6
On the causes of earthquakes on the
occasion of the calamity that befell
the western countries of Europe towards
the end of last year
editor’s introduction
A major earthquake struck off the coast of Lisbon, Portugal, on 1 November 1755, killing tens of thousands of the city’s citizens and, compounded
by flooding and fires, destroying over two-thirds of its buildings. The
magnitude of the disaster shocked the collective consciousness of Europeans. In Candide, Voltaire used the event to criticize Leibniz’s doctrine
of optimism, that ours is the best of all possible worlds, along with various other, more implicit targets. Others, taking note of the fact that the
tragedy occurred on All Saints’ Day and annihilated most of the major
churches in Lisbon, claimed that it was divine punishment for corruption
and sin. Though Königsberg was not itself directly affected, Kant wrote,
in quick succession, three essays that attempted to reassure its citizens
that the events attending the earthquake were not to be viewed as an
unspeakable evil inconsistent with God’s existence and the perfection of
the world or as an act of divine vengeance for the decadent behaviour of
Lisboans. Instead, he endeavoured to show that earthquakes have purely
physical causes and that they should therefore incite not fear, which is, in
any case, a very weak motive for virtuous behaviour in his view, but rather
careful thought about how best to control their effects (by engaging in,
for example, appropriate urban planning).
Kant published the first essay, “On the causes of earthquakes on the
occasion of the calamity that befell the western countries of Europe
towards the end of last year”, in two instalments, in the 24 and 31
January issues of the Wöchentliche Königsbergische Frag- und AnzeigungsNachrichten of 1756. His main contention in this essay is that earthquakes are caused by the conflagration of a mixture of iron filings,
sulphur, or vitriolic acid, and water that has been compressed in extensive
caverns lying below the Earth’s surface (both under land and under the
ocean floor). He also argues that earthquakes are connected with volcanic
activity, which have the same cause. He denies that they are caused by
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electricity, but allows for a connection with magnetic materials and atmospheric changes. Further, he argues that the frequency and direction of
earthquakes in mountainous regions is consistent with his view of the
cause of earthquakes.
In its most general features, Kant’s views were not particularly novel,
displaying similarities with the views of Nicholas Lémery, Christian
Wolff, Georg Erhard Hamberger, Pierre Bouguer, and Johann Heinrich
Winkler. It contrasts in both content and style, however, with, for example, Johann Gottfried Krüger’s Gedancken von den Ursachen des Erdbebens,
nebst einer moralischen Betrachtung [Thoughts on the Causes of the Earthquake, along with a Moral Observation], also published in 1756, which
consists of thirty-five pages of explanation of earthquakes on the basis of
electricity and 170 pages, consisting mostly of moralizing reflections.
further reading
Braun T. E. D. and J. B. Radner (eds.). The Lisbon Earthquake of 1755: Representations and Reactions (Oxford: The Voltaire Foundation, 2005).
Kendrick, T. D. The Lisbon Earthquake (London: Methuen & Co., 1956).
Kozák, Jan T., Victor S. Moreira, and David R. Oldroyd. Iconography of the Lisbon
Earthquake (Prague: The Geophysical Institute of the Academy of Sciences of
the Czech Republic, 2005).
Oldroyd, David, Filomena Amador, Jan Kozák, Ana Carneiro, and Manuel Pinto.
“The Study of Earthquakes in the hundred years following the Lisbon Earthquake of 1755”, Earth Sciences History 26 (2007): 321−370.
328
On the
Causes of Earthquakes
on the Occasion of the Calamity
that
befell
the Western Countries of Europe
towards the end of last year.
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Great eventsv that affect the fate of all mankind rightly arouse that commendable curiosity, which is stimulated by all that is extraordinary and
typically looks into the causes of such events. In such cases, the natural philosopher’sw obligation to the public is to give an account of the
insights yielded by observation and investigation. I do not [however] propose to satisfy this obligation in its entirety, and leave it to that person,
if such a one should arise, who can claim to have observed the Earth’s
interior with exactness. My account will only be an outline.x To make
clear what I propose, it will contain almost everything that can, as yet, be
said with any probability about this [subject], but not enough, of course,
to satisfy that strict judgement which tests everything with the touchstone of mathematical certainty. We dwell peacefully on ground whose
foundations are shaken from time to time. Without concern, we build
over cavitiesy whose supports sometimes sway and threaten to collapse.
Unperturbed by the fate that is perhaps not [so] distant from us, we give
way to pity rather than fear when we observe the devastation caused in
neighbouring places by the destruction lying hidden beneath our feet.
It is doubtless the goodness of Providence that lets us be unaffected by
fear of such fates, which cannot be prevented in the slightest by any
amount of worry, and that we should not increase our actual suffering
[unnecessarily] by fear of what we recognize as possible.
The first thing to be observed is that the ground under us is hollow and
its caverns extend very widely, almost in a single interconnected system,
even under the floor of the sea. I quote no historical examples in this
connection; it is not my intention to write a history of earthquakes. The
terrible noise heard in association with many earthquakes, like the raging
of a subterranean storm or the driving of heavy carts over cobblestones,
the continued effect [felt] simultaneously in widely separated places, of
which Iceland and Lisbon, which are separated by more than four-anda-half hundred German miles1 of sea and were set in motion on the
same day, deliver irrefutable testimony, all these phenomena agree in
confirming the interconnections of these subterranean caverns.
I should have to go back to the history of the Earth [at the time]
of the original chaos to say anything intelligible about the causes that
produced these caverns when the Earth was formed. Such explanations
will seem too much like fabrications if they cannot be presented with all
the arguments that would make them credible. Whatever their cause,
one thing is certain, namely that the direction of the caverns is parallel
to the mountain ranges, and, by a natural connection, to the great rivers
also. For these occupy the lowest parts of long valleys bounded on both
sides by parallel mountains. This is also precisely the direction in which
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Entwurf
Gewölbern
On the causes of earthquakes
earthquakes usually extend. In the earthquakes that have affected the
greater part of Italy, an almost exactly north–south motion has been
observed in the lanterns in the churches, and the recent earthquake was
from west to east, which is also the main direction of the mountains
running through the highest part[s] of Europe.
If human beings are permitted to use foresight in [the face of] such
terrible catastrophes, and if it is not regarded as a foolhardy and futile
effort to oppose general misfortune with some precautions suggested
by common sense, then should not the unhappy survivorsz of Lisbon
hesitate to rebuild along the length of the same river that indicates the
direction along which earthquakes must naturally occur in that country?
Gentil∗,2 asserts that if a city is shattered along its longer axis by an
earthquake running in the same direction, all the houses are knocked
down, but if the direction is transverse, only a few fall over. The reason
is obvious. The swaying of the ground moves the buildings out of their
vertical positions. Now if a row of buildings is shaken in this way from
east to west, then not only does each one have to carry its own weight, but
those on the west also press simultaneously on those on the east, and thus
inevitably destroy them. But if they are moved transversely, where each
has to maintain only its own balance, less damage will be caused under the
same circumstances. The catastrophe at Lisbon thus seems to have been
exacerbated by its position along the banks of the Tagus. And for this
reason, any town in a country where earthquakes have been experienced
several times, and where their direction can be known from [previous]
experiences, should not be laid out in a direction that is the same as
that of the earthquakes. However, in such cases most people are of quite
a different opinion. Since fear robs them of [the capacity for rational]
thought, they believe they can see in such widespread misfortunes a
kind of evil quite different from those [calamities] against which one is
justified in taking precautions. They imagine that they may [help to]
mitigate the severity of their fate by the blind submission with which
they yield unconditionally to it.
The main line of earthquakes follows the direction of the highest
mountains, and thus the countries that are chiefly affected are close
to these, especially if they are enclosed by two mountain ranges, in
which case the tremors combine from both sides. In a flat region, unconnected to any mountains, tremors are less common and weak[er]. This
is why Peru and Chile are more subject to frequent tremors than any
other countries in the world. In these countries, one may observe the
∗
Gentil’s Journey Around the World, as quoted by Buffon. He also confirms that the
direction of the earthquakes almost always runs parallel to the direction of large rivers.
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precaution of building houses of two storeys, of which only the lower
is made of stonework while the upper is built of reeds and light timber
so that no one will be crushed under it. Italy and indeed the island of
Iceland, part of which is in the Arctic, and other high regions of Europe,
confirm this. The earthquake that spread from west to east last December through France, Switzerland, Swabia, the Tyrol, and Bavaria, largely
followed the line of the highest regions in this continent. But it is also
known that all the main mountain ranges send out subsidiary branches
in a crosswise direction. In these, the subterranean conflagration also
spreads gradually outwards and consequently, having reached the high
regions of the Swiss mountains, it also ran through the caverns that run
parallel to the River Rhine, right into Lower Germany. What can be the
cause of this law whereby nature has linked earthquakes with the high
regions in particular? If it is agreed that a subterranean conflagration
causes these tremors, then one can easily see that because the caverns in
mountainous regions are more extensive, the emission of inflammable
vapoura there is less restricted, and the association with the air trapped
in the subterranean regions, which is always necessary for combustion,
will be freer. In addition, our knowledge of the interior composition of
the surface of the Earth, insofar as human beings are able to discover
it, teaches that the layers in the mountainous regions are not nearly so
thick as those in flat lands and the resistance to tremors is much less in
the former than the latter. If, therefore, one were to ask whether our
Fatherland has cause to be afraid of such catastrophes, then, if it were
my vocation to preach the improvement of morals, I would let the fear
of them stand in view of the general possibility [of such events] which
cannot, of course, be ruled out. But since, among the [various] motives
for piety, those that originate in [the fear of] earthquakes are doubtless
[among] the weakest, and it is my intention to adduce only physical reasons for supposing that earthquakes may occur, then one can easily see
from what I have said so far that, since Prussia is not only a land without
mountains, but must also be considered as a continuation of an almost
entirely flat land, the measures of Providence give us more cause for
hope than otherwise.
It is now time to say something about the cause of earthquakes. It is
easy for a natural philosopherb to reproduce their manifestations. One
takes twenty-five pounds of iron filings, an equal amount of sulphur,
and mixes it with ordinary water, buries this paste one or one-and-ahalf feet underground and compresses the earth firmly above it. After
several hours, a dense vapour is seen rising; the earth trembles, and
flames break forth from the soil.3 There can be no doubt that the first
two materials are frequently found in the interior of the Earth, and
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On the causes of earthquakes
water seeping through cracks and crevices can bring them into a state of
fermentation. Another experiment produces spontaneously inflammable
vapours from the combination of cold materials. Two drams of oil of
vitriol combined with eight drams of water, when poured onto two drams
of iron filings, bring forth a violent effervescence and vapours, which
ignite spontaneously. Who can doubt that vitriolic acid and iron particles
are contained in sufficient quantity in the interior of the Earth? Now if
water is added and occasions their reciprocal action, they give off vapours
that endeavour to expand, make the ground shake, and break out in flames
at the orifices of the volcanoes.
It has long been observed that a country is relieved of its violent earthquakes if a volcano has broken out in the vicinity, for it is by this means
that the enclosed vapours find an exit. And it is known that around Naples
the earthquakes are much more frequent and terrible when Vesuvius has
been dormant for a long time. In this manner, what frightens is often
beneficial, so that if a volcano were to open up in the mountains of
Portugal, it could herald the gradual departure of the misfortune.
The violent motion of water that was felt on so many coasts on that
unfortunate All Saints’ Day, is the most remarkable object of interest and
enquiry in relation to this event. It is well known that earthquakes extend
beneath the sea and cause ships to shake as violently as if they were in an
earthquake on dry land. However, in the areas where the water surged
up there were no signs of earthquakes; at least none could be felt at a
moderate distance from the coast. Nonetheless, this motion of water is
not entirely without precedent. In 1692, something similar was observed
on the coasts of Holland, England, and Germany at the time of an almost
universal earthquake. I gather that many are inclined to believe, and not
without reason, that the surging of the waters [near Lisbon] arose from
a continued shaking that the sea received off the Portuguese coast, from
the direct impact of an earthquake. [However,] this explanation appears
to be subject to some initial difficulties. I can understand very well that in
a liquid any pressure must be felt throughout the whole mass,c but how
could the pressure of the water of the Portuguese sea still raise the water
at Glückstadt and Husum4 by several feet, and that after spreading for
several hundred [German] miles? Does it not seem that mountain-high
waves would have to occur there [i.e., near Portugal] to create hardly
discernible waves here [i.e., on the Schleswig-Holstein coast, etc.]? I
answer that there are two ways in which a liquid might be set in motion
throughout its mass by a cause acting locally: either through the swaying
motion of rising and falling, that is, in a wave-like manner; or through a
sudden pressure that gives an impulse to the mass of water in its interior,
and repulses it as if it were a solid body without giving it time to evade the
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pressure by means of a wave-like surge and [thereby] dissipate its motion
gradually. The first alternative is undoubtedly insufficient to account for
the event referred to. But as far as the latter is concerned, if one considers
how water resists a sudden violent pressure as if it were a solid body, and
this lateral pressure spreads out with such violence as not to allow the
adjacent water to rise above the horizontal, [and] if one considers, for
example, the experiment of Herr Carré in the second part of the Physical
Transactions of the Academy of Sciences, page 549, where a musket ball was
shot into a box made of two-inch boards filled with water, and the water
was so compressed that the box was quite blown apart,5 [then] this gives
one an idea of the way in which the water is caused to move during
an earthquake. If one imagines, for example, that the whole west coast
of Portugal and Spain from Cape St Vincent to Cape Finistère, about
100 German miles, were shaken, and if one supposes that this quake
extended an equal distance westward into the sea, then 10,000 square
German miles of the bottom of the sea were raised by a sudden quake
whose speed we do not exaggerate if we equate it with that produced
by a powder mine that throws a body lying on it fifteen feet into the
air, and is thus capable (according to the principles of mechanics) of
travelling 30 feet per second. The overlying water resisted this sudden
shock to such an extent that it did not, as happens in slow motions,
yield and rise in waves, but received its whole pressure and drove the
surrounding water, which is to be regarded as a solid body when there
is such a rapid compression,d to the side with the same force [as that
which it received from the earthquake]. Consequently, the extremities
move with the same speed as that [water] which is directly affected [by
the impulse]. Thus in every baulke of liquid, if I may use this expression,
regardless of whether it is two or three hundred miles long, there is no
diminution of motion, if it is regarded as being enclosed in a canal with
equal openings at each end. But if the far end is larger, then conversely,
the motion through it will be correspondingly reduced. Now one must
think of the continuation of the water’s motion around itself as extending
in a circle, the circumference of which increases with the distance from
the centre. So at the periphery the flow of water is decreased in the
same measure. Thus it will be found to be six times less at the Holstein
coast, which is three hundred German miles from the assumed centre of
the earthquake, than on the Portuguese coast, which according to our
assumption is fifty miles from that [central] point. The motion on the
Holstein and Danish coast will therefore still be great enough to traverse
five feet per second, equal to the forcef of a very fast river. Against this,
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On the causes of earthquakes
it might be objected that the transmission of the pressure to the waters
of the North Sea can only occur through the channel at Calais so that its
agitation must diminish markedly through being dissipated into a wide
sea. However, if one considers that the pressure of water between the
French and English coasts before it reaches the channel must, as a result
of being compressed between these two countries, increase to the same
extent as it is subsequently diminished by expansion, then there is no
significant loss of the effects of the earthquake on the aforementioned
Holstein coast.
The most extraordinary thing about this compression of water is that
it was felt even in lakes with no visible connection with the sea, as at
Templin6 and in Norway. This seems to be almost the strongest evidence ever advanced to show that there are subterranean connections
between land-locked lakes and the sea. In order to avoid the counterargument based on the equipoise [of the waters], one would have to
imagine that the water of a lake constantly flowed downwards through
channels connecting it with the sea, but because these channels are
narrow and because the water that they lose in this way is sufficiently
replaced by inflowing streams and rivers, the out-flow is not discernible.
Nonetheless, one should not form an over-hasty conclusion concerning so strange an occurrence. For it is not impossible that the disturbance
of the inland lakes might result from other causes. The subterranean air,
set in motion by the raging fire, could well force its way through cracks
in the Earth’s strata that are normally blocked except on such occasions
of violent eruption. Nature reveals herself but gradually. One should not
seek impatiently to discover by fabrication what she conceals from us,
but wait until she reveals her secrets in distinct activities.
The cause of earthquakes seems to extend its effect into the atmosphere. Some hours before an earthquake occurs, a red sky and other
indications of altered atmospheric conditions have been observed. Animals become terrified shortly beforehand. Birds take refuge in houses.
Rats and mice scurry out of their holes. At this moment, there can be no
doubt that the heated vapour, which is on the point of ignition, breaks
through the upper vault of the Earth’s crust. I would not venture to say
exactly what effects are to be expected. But at least [we can say that]
they are not pleasing to the natural philosopher,g for what hopes does
he have of ascertaining the laws according to which changes occur in the
air when a subterranean atmosphere is interfering with their effects, and
can one doubt that this must take place frequently, for how else may we
explain the fact that there is no regularity in the changes in the weather,
because the causes of these changes are partly constant and partly
periodic?
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Note. In the previous issue7 the date of the earthquake in Iceland is
to be corrected from 1 November to 11 September, in accordance with
the report in the 199th issue of the Hamburger Correspondent.
The present observations are to be regarded as a small preliminary
exercise on the memorable natural event that occurred in our time. Its
importance and various peculiarities move me to communicate to the
public a detailed history of this earthquake, its spread over the countries
of Europe, the noteworthy things that happened during its course, and
the observations to which they can give rise, in a more detailed treatise,
which will be published in a few days by the Royal Court and Academic
Press.
336
7
History and natural description of the most
noteworthy occurrences of the earthquake
that struck a large part of the Earth at the
end of the year 1755
editor’s introduction
This essay is the second and most detailed of Kant’s writings on earthquakes in response to the Lisbon disaster. It was published as an independent piece by Johann Heinrich Hartung’s press in Königsberg. The
imprimatur was dated 21 February 1756, and it was advertised in the
11 March issue of the weekly Königsbergische Frag- und AnzeigungsNachrichten.
In this essay Kant intends to give a more detailed description and
explanation of the Lisbon earthquake and the events surrounding it.
He reports that the earthquake was preceded by a vapour rising into
the air that turned red in the atmosphere and made the torrential rains
that ensued blood-red as well. He explains these atmospheric phenomena on the basis of the iron compounds contained in the mixture of
substances that, through fermenting and being heated, led to the subterranean conflagration that caused the main earthquake. He then describes
the tsunami caused by the earthquake, its effects in distant places, its
speed of transmission and extent as well as its influence on springs,
and the mode of transmission of these effects (through the compression
of the water), distinguishing, to the extent possible, what effects are due to
the subterranean explosions and what to those of the tsunami. Kant also
describes the series of aftershocks on 18 November, 9 December, and
26 December as well as patterns in the intervals between these tremors.
He then theorizes about what geographical features are most conducive
to earthquakes and the directions of motion of an earthquake. He also
speculates, somewhat freely, about the connection between earthquakes
and the seasons and the influence of earthquakes on atmospheric conditions as well as their potential uses. Kant concludes this essay with a
sketch of a theodicy, according to which man often inappropriately views
himself rather than nature as a whole as the object of God’s actions, and,
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in addition, man is in no position to know God’s intentions in any specific case. Instead, one must assume that God’s wisdom will subordinate
lower purposes to higher ones in accordance with the noblest of aims. In
this way, there are, Kant suggests, no theologically unacceptable moral
implications of the disaster that befell Lisbon in 1755.
338
History and Natural Description
of the Most Noteworthy
Occurrences of the Earthquake
That struck a
Large Part of the Earth
at the End of the Year 1755
by
Immanuel Kant, M.A.
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It is not in vain that nature has spread out a treasury of curiosities everywhere for our observation and admiration. Man, to whom the husbandry
of the Earth’s surface has been entrusted, has the capacity and the desire
to familiarize himself with them, and praises the Creator through his
insights. Even the terrible instruments by which disaster is visited on
mankind, the shattering of countries, the fury of the sea shaken to its
foundations, the fire-spewing mountains, invite man’s contemplation,
and are planted in nature by God as a proper consequence of fixed laws
no less than other accustomed causes of discomfort which are thought
to be more natural merely because they are more familiar.
The contemplation of such terrible occurrences is instructive. It gives
man a sense of humility by making him see that he has no right, or at least
that he has lost any right, to expect only pleasant consequences from the
laws of nature that God has ordained, and perhaps he will learn thereby
to realize how fitting it is that this [present] arenah of his desires should
not contain the goal of all his aspirations.i
PREFACE.j
concerning the nature of the interior of
the earth.
1:432
So far as its extent is concerned, we know the surface of the Earth
fairly completely. However, we have another world beneath our feet
with which we are at present but little acquainted. The fissures in the
mountains that open up unfathomable depths to our plumb bobs, the
caves that we discover inside mountains, the deepest mine-shafts, which
we have extended for centuries, are utterly inadequate to give us any
distinct familiarity with the internal structurek of the huge globel we
inhabit.
The greatest depth to which people have reached from the upper
surface of the ground is less than 500 fathoms, that is, not even one six
thousandth part of the distance to the centre of the Earth. Yet these
cavities occur up in the mountains although the whole of dry land is [in
a sense] a mountain, for to reach even the bottom of the sea one would
have to descend at least three times deeper.
But those things which nature conceals from view and from our direct
investigation she reveals by their effects.m The [recent] earthquakes have
revealed to us that the surface of the Earth is full of vaults and cavities,
and that mines with manifold labyrinths running everywhere are hidden
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Vorbereitung
k
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inwendigen Bau
Klumpen
Wirkungen
History and description of the earthquake of 1755
beneath our feet. What follows in the history of the earthquake will place
this beyond doubt. We must ascribe the same origin to these caves as that
which gave rise to the sea-bed. For it is certain that even if one is only
moderately well informed about the relics left behind throughout the dry
land by the ocean after its former presence there, of the immeasurable
heaps of shells that are found even in the insides of mountains, of petrified
sea animals that are unearthed from the deepest [mine] shafts, then it
can readily be seen: first, that long ago the sea covered the entire land
for a long period; [second,] that this inundation lasted a long time and
predated the Great Flood; and finally that the waters could not have
receded by any other means than that the sea-floor sank from time to time
into deep cavities and formed deep basins into which the water flowed
and between the shores of which it is still confined. Meanwhile, the
raised areas of this sunken crust have become dry land [but] everywhere
undermined by caverns. This [dry land] is covered with steep peaks,
which we call mountains. The peaks run along the greatest heights of
the dry land in those directions in which it extends for some considerable
distance.
All these caverns contain a blazing fire, or at least an inflammable
material requiring only a slight excitationn to rage violently and shatter
or even split the overlying ground asunder.
If the whole extent of this subterranean fire is considered, then we
have to admit that there are few countries on Earth that have not felt its
effects occasionally. In the furthest north, the island of Iceland is subject
to the most violent and frequent earthquakes. There have been some
mild tremors in England and even in Sweden. Nonetheless, they are to
be found more frequently and violently in the southern lands, [by which] I
mean [those] near the Equator. Italy, and the islands in all the seas close
to the Equator, especially those in the Indian Ocean, are frequently
subject to this disturbance of their foundations. Among the latter, there
is hardly one that does not have a mountain which spews forth fire, either
at present or at least in the past; and they are just as frequently subject to
earthquakes. It is for this reason that the Dutch employ a nice precaution,
if we can believe Hübner’s report.1 In order to avoid the risk of [the
source of] the valuable spices, nutmegs, and cloves being destroyed by
an earthquake, they maintain a nursery for the plants on an island far
removed from the islands of Banda and Amboina, which are otherwise the
only places where they permit the cultivation of these species [and] which
might be totally destroyed by an earthquake. Peru and Chile, which are
close to the Equator, are troubled by this evil more frequently than any
other countries. In the former country, hardly a day passes without some
slight tremors being felt. It should not [however] be supposed that this
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is a consequence of the far greater heat of the Sun that affects the soil
of these lands. In a cellar barely forty feet deep, there is hardly any
difference felt between summer and winter. So little [therefore] is the
heat of the Sun able to penetrate the soil to great depths, and to attract
the inflammable [matter] and set it in motion. Rather, the earthquakes
are determined by the nature of the subterranean caverns. And these
follow the law according to which the collapses of the upper crust must
have occurred in the beginning, in such a manner that the closer they are
to the Equator the deeper and more numerous are the indentations they
have made, and as a result of which these mines containing the tindero
for the earthquakes have become enlarged and are consequently better
suited to ignition.
This formationp of subterranean passages is of no small importance
for understanding that which follows concerning the wide extent of the
earthquakes in large countries, of the lines they follow, the places where
they occur most frequently, and where they originate.
I now begin with the history of the latest earthquake itself. By this
I mean not a history of the instances of misfortune that people have
suffered as a result of it, nor a list of the cities and their inhabitants
destroyed under its debris. All the terrible things the imagination can
conceive have to be taken together to understand even to a small extent
the horror people must experience when the Earth moves under their
feet, when everything around them crashes to the ground, when a body
of water moved in its foundations completes their misfortune through
flooding, when the fear of death, the despair at having lost all one’s
earthly goods, and finally the sight of other people in misery must dishearten even the most courageous. A narrative of such events would be
moving, and it would, since it has such an effect on the heart, perhaps
also have the effect of improving the latter. But I shall leave this story
to more skilful hands. Here I shall only describe the work of nature,
and the remarkable natural circumstances that accompanied the terrible
event together with its causes.
concerning the harbingers of the late
earthquake.
The prelude to the subterranean conflagration that proved to be so terrible subsequently I see in the atmospheric phenomena that were perceived in Locarno in Switzerland on 14th October last year [i.e., 1755] at
8 o’clock in the morning. A vapour as warm as if it were coming out of an
o
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History and description of the earthquake of 1755
oven spread [over the area] and within two hours turned into a red mist
which developed into a blood-red rain towards the evening, which, after
it had been collected, deposited 1/9th of [its volume as] a reddish, sticky
sediment. The six-foot deep snow was similarly dyed red. This red rain
was seen for 40 hours, over an area of about 20 German miles square,
indeed as far away as Swabia. Upon this atmospheric phenomenon followed unnatural torrents of rain, which yielded up to 23 inches of water
in 3 days, which is more than is deposited in a country of moderate rainfall in a whole year. This rain lasted for more than 14 days, although not
with the same intensity for the entire period. The rivers in Lombardy
that have their source in the Swiss mountains, and the Rhône as well,
swelled as a result of this water and burst their banks. Thereafter, terrible
hurricanes prevailed in the atmosphere and these raged everywhere with
cruel force. As late as in the middle of November, a similar red rain fell
in Ulm, and the disorder in the atmosphere, the whirlwinds in Italy, and
the exceedingly wet weather continued.
If one wishes to get some idea of the causes of this phenomenon and its
consequences, one should consider the nature of the ground over which
it took place. All the Swiss mountains have extensive caverns beneath
them, which are undoubtedly connected to the deepest subterranean
passages. Scheuchzer2 has counted nearly twenty chasms that blow out
winds at certain times. Now if we assume that the minerals hidden in
these caves have come to be mixed with the liquids that cause them
to effervesce and thus start to ferment inwardly, thereby preparing the
combustible materials for that conflagration which was to break out fully
within a few days; if, for example, we imagine the acid contained in
spirit of saltpetre, and which is necessarily prepared by nature herself,
attacking the ferruginous earth upon which it fell, having been set in
motion either by the influx of water or by some other cause, then these
materials will have been heated when they were mixed and will have
emitted warm, red warm vapours from the chasms in the mountains; in
the violence of the effervescence, particles of the red ferruginous earth
were both mixed with and carried up by these vapours, and this caused
the aforementioned sticky blood-red rain. The nature of such vapours
tends to lessen the tensionq of the air and thus to make the water vapours
suspended therein coalesce; also, the concentration of all the moist clouds
hovering in the surrounding atmosphere as a result of the natural fall of
the land in the direction where the height of the column of air had been
reduced, caused the heavy and continuous downpours observed in the
areas mentioned.
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Thus, by means of expelled vapours, the subterranean fermentation
gave forewarning of the disaster it was preparing in the hidden depths.∗
Fate then took its full course in gradual steps. Fermentation does not
break out into a conflagration immediately. The fermenting and heated
materials have to meet with combustible oils, sulphur, bitumen or something similar in order to ignite. The heating process spread to and fro
in the subterranean passages until the dissolved flammable materials in
the mixture, and the other [materials], had been heated to the point of
combustion, and then the vaults of the earth were shattered and the
catastrophe reached its conclusion.
the earthquake and the motion of water of
1st november, 1755.
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The moment at which this shock occurred seems to be most accurately fixed at 9:50 a.m. in Lisbon; this time accords exactly with that
observed in Madrid, namely 10:17 to 10:18 a.m., if one converts the longitude of both cities into a time difference. At the same time, the waters
were shaken over an astonishing area, [not only] those that have a visible
connection with the ocean but also those where the connection may be
hidden. From Abo in Finland to the West Indian archipelago few if any
coasts escaped the quake. It affected an area of 1,500 miles in almost the
same space of time. If one could be sure that the time at which it was
felt at Glückstadt on the Elbe could be fixed, as reported in the public
news, at precisely 11:30 a.m., then one would conclude that the motion
of water took 15 minutes to travel from Lisbon to the coasts of Holstein. It was also felt within precisely this time on all the coasts of the
Mediterranean, and its full extent is not yet known.
Waters on the mainland that seem to be cut off from all communication with the ocean, [such as] wells [and] lakes, were set in extraordinary
motion simultaneously in countries far distant from each other. Most of
the lakes in Switzerland, the lake at Templin in Brandenburg and some
lakes in Norway and Sweden took on a surging motion, much more violent and chaotic than in a storm, yet the air was still at the time. If the
news may be relied on, the lake at Neuchâtel flowed [away] into hidden clefts, and the lake at Meiningen3 did likewise but soon returned.
In these same [few] minutes, the mineral water at Töplitz4 in Bohemia
suddenly ceased to flow and then returned blood-red. The forcer with
∗
Eight days before the earthquake, the ground at Cadiz was covered by a great many
worms that had crawled out of the earth. These had been driven out by the cause just
mentioned. In the case of several other earthquakes, violent lightning in the air and the
apprehension observed in animals have been harbingers.
r
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which the water was pushed through enlarged its former passages, and
thus it gained a stronger inflow. The inhabitants of that town had good
cause to sing Te Deum laudamus, while those in Lisbon began to sing in
quite different tones. Such is the nature of the accidents that affect the
human race. The joy of one group and the misery of another often have
a common cause. In the Kingdom of Fez in Africa, a subterranean forces
split open a mountain, which poured blood-red streams from its depths.
At Angoulême in France a subterranean roar was heard, and a deep
chasm opened on the plain, containing bottomless water. In Gémenos
in Provence, a well suddenly became turbid and then poured forth in
a red colour. The surrounding areas reported similar changes in their
wells. All this occurred in the same [few] minutes when the earthquake
was devastating the coasts of Portugal. In just this same short period of
time several earthquakes were felt in far distant countries. But nearly all
of them took place near the sea coasts. In Cork in Ireland, as in Glückstadt
and several other places situated on the sea, there were slight tremors.
Milan is probably the place furthest from the sea to have experienced an
earthquake on that day. On the very same morning at 8 o’clock, Mount
Vesuvius near Naples erupted, and then became quiet around the time
when the earthquake occurred in Portugal.
observation on the cause of this
motion of water.
History has no precedent for so widespread a disturbance of water and a
large part of the Earth observed in the space of a few minutes. One should
therefore be cautious in inferring its causes from what was a unique
event. [Nevertheless,] one can have particular regard to the following
causes that may have brought about the aforementioned event; [namely]
a general quaking of the sea-floor directly under those areas where the
sea was disturbed. But then one would have to indicate why the vein of
fire responsible for these earthquakes ran only under the bottom of the
seas, without extending to the lands that are in close connection with
the latter and are often interposed between them. It would be difficult
to explain why this disturbance of the ground, which extended from
Glückstadt on the North Sea to Lübeck on the Baltic, and along the
coast of Mecklenburg, was not felt in Holstein, which lies between these
two seas, and where only a very slight tremor was felt on the coast but
none was felt inland. Even so, the most convincing thing is the surging of
the waters far from the ocean, such as occurred at the lakes at Templin,
in Switzerland and elsewhere. It is easy to see that, in order to bring
a body of water into such violent agitation, the shock must be quite
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considerable. But why was this mighty quake not felt in the surrounding
lands under which the vein of fire must needs have run? It is easy to see
that all the evidence is against this opinion. It is extremely unlikely that
an earthquake impressed itself upon the surrounding solid mass of the
Earth itself by a violent convulsion at one point, as the ground is shaken
for some distance around when a powder magazine explodes, and both
for the reason already mentioned and because the awesome extent [of
the catastrophe] when compared with the circumference of the Earth,
constitutes such a large proportion of the latter that its shaking would
have had to produce a shaking of the whole globe. Now one can learn
from Buffon5 that an eruption of subterranean fire capable of throwing
a mountain range of seventeen hundred miles long and forty wide a mile
into the air would not move the globe one inch from its position.
Thus we shall have to look for [the cause of] the spread of this motion
of water in some medium that is more suited to transmit a disturbance
for great distances, namely in the water of the seas themselves, which is in
[direct] connection with that which was suddenly and violently disturbed
by a direct motion of the sea-bed.
In the weekly Königsberger Anzeigen, I have tried to calculate the forcet
with which the whole sea was repulsed by the shock of the tremor on its
floor. I assumed the affected area of the sea-floor to be merely a square,
one side of which was equal to the distance from Cape St Vincent to Cape
Finistère, that is, the length of the western coast of Portugal and Spain,
and I regarded the poweru of the rising sea-bed as equivalent to a powder
mine capable of raising the bodies over it by fifteen feet, and according
to the laws by which motion is transmitted in liquids, I found it to be
stronger on the Holstein coast than the impact of the fastest running
stream. Let us here consider from a different perspective the power that
it can exercise as a result of these causes. By means of a plumb line,
Count Marsigli6 found the greatest depth of the Mediterranean to be
over eight thousand feet, and it is certain that the ocean is much deeper
at an appropriate distance from the land, but we will here assume it to
be only six thousand feet, that is, one thousand fathoms. We know that
the pressure which so high a column of water exerts on the bottom of the
sea must exceed the pressure of the atmosphere by nearly two hundred
times, and that it must far exceed the power behind a ball hurled from
a heavy cannon over a distance of one hundred fathoms in the space of
a pulse beat. This enormous load could not withstand the power with
which the subterranean fire pushed the sea-floor rapidly upwards, and
therefore this [upward] motive powerv was greater. With what pressure,
then, was the water impelled for it to shoot suddenly in all directions?
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History and description of the earthquake of 1755
And is it surprising if the shock was felt a few minutes later in Finland
and simultaneously in the West Indies? It cannot be determined how
large the area of the direct quake may actually have been. Perhaps it
was much greater than we have supposed; but it was certainly not to be
found on the sea-floor under the seas where the motion of water was felt
without any earthquake, on the Dutch, English, and Norwegian coasts,
and in the Baltic. For otherwise the dry land would undoubtedly also
have been shaken in its interior, which, however, was not observed.
In ascribing the violent quaking of all the connected parts of the ocean
to a single impact,w acting on the sea-bed in a particular area, I do not wish
to deny the actual spreading of the subterranean fire under the dry land
of almost the whole of Europe. In all probability, the two events occurred
simultaneously and both had a share in the ensuing phenomena, so that
neither individually was the sole cause of the effects as a whole. The
disturbance of the water in the North Sea, which was felt as a sudden
shock, was not the effect of a subterranean earthquake. Disturbances
would have to be very violent to bring about such effects and would
necessarily have been readily detectable on dry land. However, I do not
wish to deny that even the dry land as a whole was slightly shaken by a
weak forcex of ignited subterranean vapours, or for other causes. This
is evident from Milan, which on that day [i.e., 1st November, 1755]
was threatened by the acute danger of total collapse. Let us suppose,
then, that a feeble tremor there set the Earth in motion, which tremor
was sufficient to rock the ground back and forth by one inch over a
distance of one hundred Rhineland rods.7 This motion would have been
so imperceptible that a building of four rods in height would not have
been displaced from the vertical by half a grain [sic], that is, by half
the [thickness of the] back of a knife. This would scarcely have been
perceptible on even the highest towers. However, the lakes would have
made this imperceptible motion very evident. For if a lake is only two
German miles long, then its water will be set into a fairly strong rocking
motion by this slight motion of its floor; for the water then has a fall of
roughly one inch in fourteen thousand inches, and a speedy only slightly
less than that of a fairly fast river, such as the Seine in Paris, which
could teach us what, after some rocking to and fro, could have caused an
extraordinary disturbance in the water. But we can assume that the earth
tremor was as great again as that assumed [above] without its being felt
on dry land; and so the motion of the inland lakes appears all the more
intelligible.
Thus, it is no longer surprising if all the inland lakes in Switzerland,
Sweden, Norway, and Germany were seen to be agitated without any
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disturbance of the ground being felt. It is, however, rather more extraordinary that certain lakes disappeared altogether during this disturbance,
such as the lake at Neuchâtel, that at Como, and that at Meiningen,
although some of those have already filled up with water once again. But
this event is not without parallel. There are some lakes in the Earth that
disappear at certain times through hidden channels, and return at regular
intervals. A notable example is Lake Zirknitz in the Duchy of Carniola.8
There are some openings in its floor through which the water suddenly
runs out, complete with all its fish, but not before St James’s Day.9 And
after it has served as good arable land for three months, the water suddenly reappears about November. This natural phenomenon is plausibly
explained by comparison with the siphon in hydraulics. However, for the
cases under consideration it can easily be seen that many lakes are fed
by underlying springs that have their source in the surrounding higher
ground. When the effects of subterranean heating and the vapours it
creates have consumed the air in the caverns that hold the water for the
springs, the springs will be sucked back, thereby creating a powerful suction that drains the lake. And after the balance of the air [in the caverns]
has been restored, the lake seeks its natural exit once again. For that a
lake should maintain its level by means of a subterranean connection
with the sea because it has no external inflow from rivers, as the public
reports of Lake Meiningen have endeavoured to suggest, is obviously
absurd, for the laws of equilibrium as well as the salinity of the sea water
speak against [such a view].
A common feature of earthquakes is that they cause the disturbance
of springs. I could quote a whole list of springs being blocked up and
new ones being opened up elsewhere, of spring water shooting quite
high out of the ground, and similar occurrences from the records of
other earthquakes, but I shall keep to my subject. It was reported from
some places in France that some springs were blocked while others produced excessive amounts of water. The spring at Töplitz [in Bohemia]
stopped and the inhabitants were worried; but then the water returned,
at first slimy, and then blood-red, and finally in its natural condition and
stronger than before. The discoloration of water in so many places, even
in the Kingdom of Fez and in France, is in my view to be ascribed to
the intermingling of sulphur and small particles of iron, with the fermenting vapours forcing their way through the strata through which the
springs also pass. When these vapours reach the inside of the cisterns
containing the source of the spring, they either push it out again with
greater force,z or they change its outflow by pushing the water into other
cavities.
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These are the chief noteworthy events of the history of 1st November
and of the motion of water, which was the most remarkable of the concomitant occurrences. It is entirely credible to me that the earthquakes
that occurred near the ocean, or the shores of any water connected to
the ocean, in Cork in Ireland, in Glückstadt, and in several places in
Spain, should be attributed chiefly to the pressure of the compressed
sea water, the powera of which must be unbelievably great if one multiplies the forceb with which it strikes by the area on which it strikes,
and I am of the opinion that the disaster in Lisbon, like that of most
of the cities on the western coast of Europe, is to be attributed to the
position it had in relation to the disturbed area of the ocean, since its
whole force, magnified in the mouth of the Tagus by the narrowing of
the bay, must in addition have shaken the ground to an extraordinary
degree. From this, one may judge as to whether the earthquake would
have been felt distinctly only in the coastal towns and not in the interior
[as in fact happened], if the pressure of water had not played some part
in it.
One last phenomenonc of this great event is worth noting, where a
considerable time, one to one-and-a-half hours, after the earthquake
[there arose] a fearful upsurge of water in the ocean and a rise of the
Tagus six feet higher than the highest tide; and soon afterwards a fall to
an equal distance below the lowest tide was observed. This motion of the
ocean, which occurred a considerable time after the earthquake and after
the first terrible pressure of the waters, completed the destruction of the
town of Setubal by overwhelming the ruins and completely destroying
everything that the earthquake had spared. If a proper conception has
already been formed of the violenced of the sea water’s retreat occasioned
by the motion of the sea-floor, it will be easy to imagine that it must also
return with great violencee after its pressure has been spread into the
huge surrounding areas, and the time of its return depends on the area
that it has affected. The fearsome extent of the tidal wave on the coasts
is also dependent on the area covered.∗
the earthquake of 18th november.
From 17th to the 18th of this month the public news bulletins reported
a significant earthquake on the coasts of Portugal and Spain, as well
as in Africa. It was felt at noon on the 17th in Gibraltar at the mouth
∗
In the harbour in Husum, this tidal wave was also observed between 12 and 1, that is,
an hour later than the first shock in the waters of the North Sea.
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of the Mediterranean, and in the evening at Whitehaven in Yorkshire
in England. [During the night] of the 17th to the 18th it was already
felt in the English colonies in America. On the same 18th, it was
also strongly felt in the region of Aquapendente and della Grotta in
Italy.∗
the earthquake of 9th december.
1:444
According to news reports, Lisbon has not suffered any such violent
earthquakes since the 1st November as that on 9th December. This
was felt on the southern coasts of Spain and of France, throughout the
Swiss mountains, in Swabia, and the Tyrol all the way to Bavaria. It
travelled some 300 German miles from south-west to north-east, and,
while its direction followed the range of mountains that runs along the
length of the highest regions of continental Europe, it did not spread
very far sideways. The most careful geographers, Varenius,10 Buffon,
and Lulof,11 note that, just as any land that extends more in length
than in breadth, has a main range running along its length, so that the
principal line of mountains in Europe extends from a main stem, namely
the Alps, westwards through the southern French provinces, through
central Spain and to the most western shore of Europe, although on
the way it sends out considerable lateral branches, and equally eastwards
through the Tyrolean and other less impressive mountains until it finally
meets the Carpathian range.
It was this direction that the earthquake followed that day. If the time
of the tremor had been accurately noted at each place, it would be possible
to give some estimate of its speed, and probably one could determine
the area of the initial outbreak; but the reports are so little in agreement
that they cannot be relied upon.
I have stated elsewhere that when they spread, earthquakes usually follow the line of the highest mountain range, and for their whole length
at that, even though they become lower the more they approach the
ocean shore. The direction of long rivers is a very good indicator of the
direction of the mountain ranges, since they flow between the parallel
rows of mountains as in the lowest part of a long valley. This law of the
spreading of earthquakes is not a matter of speculation or judgement
but something that has become known through the observation of many
earthquakes. For this reason we ought to keep to the evidence of Ray,12
Buffon, Gentil,13 etc. But this law has so much inherent probability that it
must readily gain our approval by itself. If one considers that the openings
∗
Similarly in Glowson in the county of Hertford, where with a great noise, an abyss
containing very deep water opened.14
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History and description of the earthquake of 1755
through which the subterranean fire seeks a way out are only ever on the
peaks of mountains, that fire-spewing mouths have never been found on
plains, that in countries where earthquakes are violent and frequent, most
of the mountains contain broad abysses that serve to throw out the fire,
and that, as far as our European mountains are concerned, nowhere but
in them are spacious caves found that are undoubtedly interconnected;
if, in addition, one applies to all these subterranean cavities the idea
of their origin discussed above, then one will find no difficulty with
the idea that the conflagration can find open and free passages principally under the range of mountains that run the length of Europe, faster
therein than in other regions.
Even the continuation of the earthquake of 18th November from
Europe to America under the floor of a broad ocean can be found in
the links between mountain ranges, which, though their continuation is
so low that they are covered by the sea, nonetheless remain mountains
there, since, as we know, there are as many mountains to be found on the
floor of the sea as there are on land; and in this way, the Azores Islands,
which are encountered half-way between Portugal and North America,
must be connected with these [mountains].
the earthquake of 26th december.
After the heating of the mineral matter had penetrated the main stem
of the highest mountains in Europe, that is the Alps, it also opened
for itself the narrower passages under the row of mountains that run
outwards from it at right angles from south to north, and extended in
the direction of the Rhine, which, like all rivers, occupies a long valley
between two rows of mountains from Switzerland to the North Sea.
On the western side of the river, [the earthquake] shook the regions of
Alsace, Lorraine, the Electorate of Cologne, Brabant and Picardy, and
on the eastern side, Cleve, part of Westphalia, and presumably some
other countries situated on this side of the Rhine about which the news
has not reported anything specific. Evidently, it maintained a direction
parallel to this great river and extended a short distance on either side.
One may ask how the foregoing can be reconciled with the fact that
it penetrated into the Netherlands, which are without any significant
mountains. But it is sufficient that a country be in direct contact with
certain ranges of mountains and may be thought of as a continuation of
these for the subterranean conflagrations to continue under the otherwise low ground, for it is certain that the chain of caverns will extend
underneath it just as, as already explained, it continues even under the
floor of the sea.
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on the intervals between successive
earthquakes.
If the succession of earthquakes is considered carefully, then, if one
were prepared to speculate, one might work out an interval after the
conflagration broke out anew after an interim period without activity.
After 1st November, we find another very violent tremor in Portugal
on the 9th, similarly on the 18th, since it extended to England, Italy,
Africa, and even to America; on the 27th a strong earthquake on the
south coast of Spain, principally in Malaga. From this time onward, it
took 13 days, until on 9th December it struck the entire region from
Portugal to Bavaria, moving from south-west to north-east, and after
this one, after another 18 days, namely on the night of 26th to 27th
December, it shook the breadth of Europe from south to north,∗ so that
a fairly accurate period of 9 or two times 9 days passed between the
repeated conflagrations, if one excepts that time it took to penetrate the
innermost part of the mountains of our continent and to move the Alps
and the entire chain of its extension on 9th December. I cite this not
with the aim of concluding anything from it, but rather to provide an
occasion for observations and reflection when similar cases occur.
I intend to make only a few remarks here on those earthquakes that
alternately diminish and then begin again. Herr Bouguer,15 one of the
representatives of the Paris Royal Academy of Sciences who visited Peru,
had the discomfort in that country of residing next to a volcano, whose
thundering noise allowed him no rest. But the observation he made of this
phenomenon offered him some compensation, in that he noticed that the
mountain always became quiet at regular intervals, and that its violence
alternated regularly with quiet periods. The observation of Mariotte16
made with a lime kiln, which when heated up expelled air through an
open window and soon after drew it in again, thus to some extent emulating the respiration of animals, is very similar to this phenomenon. Both
have the following causes in common. When the subterranean fire is
ignited, it expels all the air from the surrounding caverns. When this air,
filled with fiery particles, finds an opening, for example in the mouth of
a volcano, it rushes out and the mountain belches fire. But as soon as the
air has been driven out from the seat of combustionf the combustion dies
∗
On the 21st it was very violent in Lisbon, on the 23rd in the mountains around Roussillon, and it continued there until the 27th. It can be seen from this that it began from the
south-west once again and required much longer to spread. If we assume the place of
origin to be in the ocean to the west of Portugal, as is clear from the entire course of the
earthquake, then its beginning is fairly closely connected with the interval mentioned.
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History and description of the earthquake of 1755
down; for without a supply of air any fire goes out; then the displaced air
returns to its place since the cause that drove it out has ceased to operate
and the air rekindles the extinguished fire. In this way, the eruptions of
a volcano alternate at certain regular intervals. It is the same with the
subterranean conflagrations, even where the expanded air can find no
way out through the clefts of the mountains. For, if the conflagration
begins at one place in the caverns of the earth, it repels the air violently
and in large quantities into all the passages of the subterranean vaults
with which it is connected. At this moment the fire is stifled by the lack
of air. And as soon as this expanding force of the air diminishes, the air
that was disseminated throughout the caverns returns with great forceg
and fans the dead fire to [cause] a new earthquake. It is noteworthyh
that Vesuvius, which had been activated and ignited by the outflow of
air expelled through its mouth when the fermentations in the interior
of the Earth got properly under way, suddenly subsided a short time
later, when the earthquake had occurred in Lisbon; for at that moment
all the air that was in connection with these vaults, even that above the
peak of Vesuvius, rushed through all channels to the seat [or epicentre]
of the conflagration, where the reduction of the elasticity of the air gave
it access. What an amazing object! Imagine a chimney which derives its
draught from air vents 200 [German] miles away!
Exactly the same cause must create subterranean storm winds in the
Earth’s cavities, the forcei of which must far exceed anything we experience on the surface, when the position and connection of the caverns
lends itself to disseminating the winds. Presumably the commotion that
is felt under foot during the course of an earthquake can only be ascribed
to this cause.
From this we can probably assume that not all earthquakes are caused
by a conflagration immediately under the ground that is being shaken;
rather, the fury of these subterranean storms can set the vaults above
them in motion, which cannot be doubted if one considers that the air,
which is far denser than that on the surface of the Earth, is set in motion
by far more sudden causes, and, increased by passages that prevent its
expansion, can exercise an untold force.j It is thus probable that the
slight motion of the ground that took place in the greater part of Europe
during the violent conflagration of 1st November, was perhaps caused by
nothing other than this violently agitated subterranean air, which gently
shook the ground that was resisting its expansion in the form of a strong
storm wind.
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on the seat of the subterranean conflagration
and the places subject to the most frequent
and most dangerous earthquakes.
1:449
By comparing the time[s], we see that the place at which the earthquake
of 1st November began was on the sea-bed. The Tagus, which had
already swelled before the earthquake, the sulphur brought up by sailors
from the shaken sea-bed with their plumb lines, and the violence of
the shocks they felt [all] confirm this. The history of earlier earthquakes
also makes it clear that the most terrifying earthquakes have always taken
place at the bottom of the sea and next to this, in places at or not far from
the shores of the sea. To prove the former, I cite the raging fury with
which a subterranean conflagration has often raised new islands from
the sea-floor and, for example, in the year 1720 near the Azores island of
St Michael, the expulsion of matter from the bottom of the sea at a depth
of 60 fathoms, threw up an island one mile long rising to several fathoms
above sea level. The island at Santorini in the Mediterranean, which
emerged in our century from the depths of the sea as witnessed by many
people, and many other examples that I will pass over for the sake of
brevity, are indisputable proofs of this.
How often do sailors suffer a seaquake! And in some regions, especially in the neighbourhood of certain islands, the seas are profusely
covered with pumice stones and other varieties of ejecta from a fire that
has broken through the ocean bed. The observation of the frequency of
earthquakes on the sea-floor is naturally related to the following question: Why is it that, of all the places on land, none are subject to
more violent and frequent earthquakes than those situated not far
from the shores of the sea? This last statement is undoubtedly correct:
if we consider the history of earthquakes we find an infinite number of
disasters that earthquakes have brought upon cities or countries near the
sea shore whereas those felt in the middle of a land mass are very few
and then of less significance. Ancient history already records the terrible
devastation this [kind of] disaster has wrought on the sea coasts of Asia
Minor or Africa. But neither with them nor with more recent ones do
we find significant earthquakes in the centre of large land masses. Italy,
which is a peninsula, most oceanic islands, and coastal Peru suffer the
greatest incidence of this evil. And even in our own time, all the western and southern coasts of Portugal and Spain have been much more
severely shaken than the interior of the mainland. To both questions I
propose the following solution.
Of all the interconnected caverns under the uppermost crust of the
earth, there is no doubt that those running under the bottom of
the sea must be the narrowest, because there the continuing base of
the solid ground has sunk to the greatest depth, and must rest far lower
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History and description of the earthquake of 1755
on its deepest foundation than places in the centre of the land. But it is
well known that an ignited, expanding matter must have a more violent
effect in narrow cavities than where it can expand [freely]. In addition, it
is natural to suppose that, since there can be no doubt that the seething
mineral and inflammable materials will very often have become liquid
when subterranean heating occurs, as is demonstrated by the sulphur
streams and lava which often pour out of volcanoes, and, on account of
the natural slope of the floor of the subterranean caverns, will always have
flowed to the lowest caves of the bottom of the sea, more frequent and
more violent tremors must take place there on account of the plentiful
supply of combustible material.
Herr Bouguer correctly supposes that the penetration of sea water by
the opening of some cracks in the sea-floor must bring the mineral matter
that is naturally inclined to heating into the most vigorous calefaction.
For we know that nothing can stimulate the fire of heated minerals into
greater fury than the ingress of water, which increases its activity to
the point where its violence,k expanding in all directions, prevents any
further inflow of water by expelling all earthy matters and blocking the
opening.
In my opinion, the great violencel that shakes land situated close to a
sea shore is partly the perfectly natural result of the weight with which
the sea water burdens its floor which adjoins this land. For everybody will
easily recognize that the force with which the subterranean fire attempts
to raise this vault, on which such an astonishing weight rests, must be
very much restrained, and, since it cannot find any space for expansion,
must turn its entire force against the base of the dry land which is most
closely connected to it.
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on the direction in which the ground is
shaken by an earthquake.
The direction in which an earthquake spreads over large areas is different
from that in which the ground on which it exerts its forcem is shaken.
If the uppermost covering of the hidden cavern in which the burning
matter is expanding has a horizontal direction, then the ground must
be alternately raised and lowered in a vertical direction because there
is nothing that might direct the motion more to one side than to the
other. But if the layer of earth that constitutes the vault is tilted, then
the disruptive force of the subterranean fire will also push it upwards
at an oblique angle to the horizon, and one could deduce the direction
in which the oscillation of the ground must occur on each occasion, if
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one had definite knowledge of the direction of slope of the layer under
which the vault of fire is situated. The slope of the topmost surface of
the shaken ground is no certain indication of the angle of the vault in its
entire thickness; for the layers of earth lying on top can form manifold
declivities and hills, which the lowest layers do not follow at all. Buffon
believes that all the different layers found on Earth have a common
basement rock that covers all enclosed cavities below it and that some
parts of it are usually exposed on the peaks of high mountains where
rain and storm winds have completely eroded the loose material. This
opinion is given strong support by the evidence of earthquakes. For a
forcen so furious as that exercised by earthquakes would, by its repeated
onslaughts, long ago have shattered and eroded any vaulting other than
one made of rock.
On the coast, the slope of this vault is undoubtedly inclined towards
the sea and thus slopes down in its direction from the place in question.
On the banks of a great river, it must slope in the direction of the flow
of the stream; for if one considers the very long stretches, often exceeding several hundred [German] miles, that the rivers run through on dry
land without creating permanent pools or lakes, then there is probably no other explanation for this uniform slope than the extremely firm
foundation, which, by sloping uniformly towards the bottom of the sea
without many depressions, provides the river with an inclined surface for
draining the water. For this reason, we can suppose that during an earthquake, the motion of the ground of a city situated on a large river will
be in the same direction as that river, as in [the case of] the Tagus from
west to east,∗ while the [motion] of a city on the sea shore will be in the
direction in which the shore slopes towards the sea. Elsewhere,17 I have
indicated what the lie of the land may contribute to the total destruction by an earthquake of a city in which the main streets follow the
slope. This note is not merely a supposition; it is a matter of experience.
Gentil, who personally had the opportunity to gather accurate information about numerous earthquakes, reports this as an observation confirmed by many examples: that, if the direction in which the ground is
shaken is the same as that in which the city has been built, it will be
demolished completely, while less damage will occur if it crosses this
direction at right angles.
The Histoire de l’Académie Royale des Sciences in Paris reports that when
Smyrna, which lies on the eastern coast of the Mediterranean, was rocked
∗
Just as a river has a slope towards the sea, the lands on its sides have a slope towards its
bed. If this last applies to the whole layer of earth, and this has just such a slope at its
greatest depth, then the direction of the earthquake will also be determined by this.
n
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History and description of the earthquake of 1755
in 1688, all the walls having a direction from east to west collapsed and
those that were built from north to south remained standing.
The fact is that the shaken ground makes repeated motions and moves
those things that are built lengthwise in the direction of the motion to
the greatest extent. All bodies that have great freedom of motion, e.g.,
chandeliers in churches, usually show the direction in which the tremors
occur and are much more reliable indicators for a city to determine the
direction in which it should build than the somewhat more doubtful
factors previously mentioned.
on the connection of earthquakes
with the seasons.
Herr Bouguer, the French Academician already referred to on several
occasions, reports in [the account of] his journey to Peru, that, even
though earthquakes occur in this country fairly often and at all seasons,
the most terrible and most frequent ones are felt in the months of autumn
towards the end of the year. This observation is confirmed not only by
numerous cases in America, for apart from the destruction of the city
of Lima ten years ago, and that of another equally populous city in
the previous century, very many examples have been noted, but also in
our part of the world we find, apart from the latest earthquake, many
other historical instances of earthquakes and volcanic eruptions that have
occurred more frequently in autumn than at any other time of the year.
Is there a common cause for this agreement, and to which cause can
one more properly attribute the supposition than to the rains which,
in the long valley between the Cordillera Mountains in Peru, last from
September until April, and are also most frequent in autumn in our own
country? We know that all that is necessary to cause a subterranean fire
is to bring the mineral matter in the caverns of the Earth into a state of
fermentation. But this is done by the water when it has seeped through
the clefts in the mountains and has run away through the deep passages.
The rains first stimulated the fermentation that expelled so many strange
vapours from the interior of the Earth in the middle of October. It was
precisely these, however, which drew forth even more humid influences
from the atmosphere, and the water, which penetrated into the deepest
cavities through cracks in the rock, completed the heating, which had
already begun.
on the influence of earthquakes
on the atmosphere.
We have seen above an example of the effects of earthquakes on our
atmosphere. It is probable that more natural phenomena are dependent
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on the eruptions of the subterranean heated vapours than is generally
supposed. It would hardly be possible for there to be such great irregularity and so little consistency in the weather if external causes did not
occasionally enter our atmosphere and bring disorder into its proper
changes. Can one imagine a likely reason why the sequence of meteorological changes is almost always different even in a sample of many years,
whereas the course of the Sun and the Moon is bound by laws that are
always the same and water and earth, taken generally, always remain constant? Since the unfortunate earthquake and shortly before it, we have
had such abnormal weather over our entire continent that one might
be forgiven for suspecting that the earthquakes were responsible. It is true
that there has been warm winter weather before without any earthquake
having preceded it; but can one be sure that there was not a fermentation in the interior of the Earth that frequently drove vapours through
clefts in rocks, through the cracks in the layers of the earth and even
through its loose substance, and that these might have caused significant
changes in the atmosphere? After observing that in the present century
alone, and indeed only since 1716, very bright Northern Lights have
been seen in Europe all the way to its southern lands, Muschenbroeck18
regards the most probable cause of this change in the atmosphere to
be the volcanoes and the earthquakes, which had frequently been active
some years previously, and had emitted flammable and volatile vapours;
and because of the natural northward flow of the upper atmosphere,
the vapours had accumulated there and brought about the fiery atmospheric phenomena which have been seen so frequently since that time,
and these will presumably be gradually consumed until new exhalations
replace what has been used up.
In accordance with these principles, let us examine whether it is not
in keeping with nature that changing weather such as we have had is a
result of that catastrophe. The bright winter weather and the accompanying cold is not merely a consequence of the greater distance of the
Sun from our zenith at this time of the year, for we often perceive that
despite this the air can be very temperate; rather, the draught of air from
the north, which sometimes can also turn into an east wind, brings us
cooled air from as far away as the Arctic Circle that covers our waters
with ice and makes us feel some of the winter of the North Pole. This
motion of air from north to south is so natural in the autumn and winter
months if external causes do not interrupt it, that this north or north-east
wind is encountered continually throughout this period in the [Atlantic]
Ocean at a considerable distance from any dry land. It originates quite
naturally from the effect of the Sun, which at that time is making the
air less dense over the southern hemisphere and thus causes it to flow
from the northern hemisphere: so that this must be considered to be a
uniform law which, though it might be altered to some extent by the
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History and description of the earthquake of 1755
features of the various countries, cannot be reversed. Now if subterranean fermentations eject heated vapours somewhere in the countries
to the south, then these will initially reduce the atmospheric pressureo
in the region where they rise by weakening the elasticity [of the air] and
causing cloudbursts, hurricanes, and so on. Subsequently, however, this
part of the atmosphere, since it is weighed down with so many vapours,
will move the neighbouring air by its density and cause a flow of air from
south to north. But since the motion of the atmosphere from north to
south is natural in our region at this time of the year, these two mutually
opposed motions will act against one another and result initially in dull,
rainy air because of the concentrated vapours, and at the same time in
a high level of barometric pressure,∗ because the air, which has been
pressed together by the conflict of two winds, must form a high column;
and for this reason, people will learn to accept the apparent error of
the barometer, when there is rainy weather even though the barometer
is high, because then this same humidity of the air is an effect of two
conflicting winds which drive the vapours together and can nonetheless
make the air significantly denser and heavier.
I cannot pass over in silence the fact that on that terrible All Saints’
Day the magnets in Augsburg cast off their burden and the compasses
were disoriented. Boyle19 has previously reported that something similar
once occurred after an earthquake in Naples. We do not know enough
about the hidden nature of the magnet for us to be able to give a reason
for this phenomenon.
on the uses of earthquakes.
People will be shocked to find such a terrible scourge of humanity praised
from the point of view of utility. I am sure that people would gladly do
without it in order to be relieved of the fear and the associated dangers. Such is our nature as human beings. Once we have laid an illegitimate claim to all the pleasant things in life, we are not prepared to pay
the cost of any advantages. We demand that the Earth’s surface should
be so constituted that one might wish to live on it forever. In addition,
we imagine that we would better regulate everything to our advantage,
if fate had asked for our vote on this matter. Thus we wish to have
e.g. the rain in our power so that we could distribute it over the whole year
in accordance with our convenience and so could always enjoy pleasant
days between the dull ones. But we forget the wells, which we cannot do
without and which would not be maintained under this system. Equally
∗
This has been observed almost constantly in this wet winter weather.
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Höhe des Luftkreises
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we do not know the use which is brought to us by the same causes that
frighten us in the case of earthquakes, and yet we should like to see the
latter abolished.
As human beings, who were born to die, we cannot tolerate the fact
that some died in the earthquake, and as strangers here who possess no
goods we are inconsolable that goods were lost which in the general
nature of things would soon have been left behind anyway.
It is easy to guess that, if people build on ground that is filled with
flammable matters, then sooner or later the whole glory of their buildings could be destroyed by earthquakes; but must we therefore become
impatient with the ways of providence? Would it not be better to conclude that it was necessary for earthquakes to occur occasionally on the
Earth, but it was not necessary for us to erect splendid houses on it? The
inhabitants of Peru live in houses that are built with mortar only up to
a low height and the rest consists of reeds. Man must learn to adapt to
nature, but he wants nature to adapt to him.
Whatever damage earthquakes may, on the one hand, ever have caused
for man, they can, on the other hand, easily replace with interest. We
know that the warm baths, which over the course of time may have been
useful to a significant proportion of mankind in promoting health, derive
their mineral properties and their heat from just the same causes that are
at work in the heating of the Earth’s interior, which set these [waters] in
motion.
It has long been suspected that the veins of ore in the mountains are a
slow effect of the subterranean heat, which brings the metals to maturity
through a gradual process of shaping and boiling them by means of
penetrating vapours in the rock’s interior.
In addition to the coarse and dead matters it contains, our atmosphere
also needs a certain active principle, volatile salts and parts that enter
into the composition of plants, to move and developp them. Is it not
likely that the natural forms that continually expend a large part of it,
and the changes that all matter ultimately undergoes through dissolution
and composition, would in time entirely use up the most active particles if there were not a fresh influx from time to time? The soil at least
becomes less and less potent when it feeds strong plants, but rest and
rain restore it again. But where, finally, would the potent material that
is used without replacement come from if there were no other source
to maintain its supply? And this source is presumably the store of these
most active and volatile substances which the subterranean caverns contain, some of which they distribute from time to time over the surface
of the Earth. I also note that Hales20 has had great success in purifying
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auszuwickeln
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History and description of the earthquake of 1755
gaols and indeed all other places affected by animal exhalations by fumigating them with sulphur. Volcanoes expel an immeasurable amount
of sulphurous vapours into the atmosphere, [so] who knows whether
the animal exhalations with which the air is laden would not eventually
become harmful if the volcanoes did not provide a powerful antidote to
them?
Finally, it seems to me that the heat in the interior of the Earth provides a powerful proof of the effectiveness and great utility of the heating
that takes place in the deep caverns. Daily experience shows that in the
great, indeed the greatest depths that men have reached in the interior of mountains, there is a permanent heat which cannot possibly be
ascribed to the effect of the Sun. Boyle cites a good deal of evidence which
shows that, in all the deepest shafts, the upper region is found to be
much cooler than the outside air in the summer, but that the deeper
one descends, the warmer the region, so that at the greatest depths, the
workers are obliged to take off their clothing while they work. Everyone
will easily grasp that, since the warmth of the Sun penetrates the Earth to
only a very slight depth, it cannot have the slightest effect in the very lowest caverns, and the fact that the warmth encountered there is the result
of a cause that prevails only in the greatest depths can also be seen from
the reduced warmth that is experienced the more one ascends even in
the summer. After carefully comparing and examining the experiments
carried out, Boyle concludes very reasonably that, in the lowest caverns,
which are inaccessible, there must be constant heating processes and an
inextinguishable fire maintained thereby which transmits its warmth to
the uppermost crust.
If this is indeed the case, as one cannot but concede, will we not be able
to expect the most beneficial effects from this subterranean fire, which
always maintains a gentle warmth for the Earth at the time when the
Sun withdraws its warmth from us, and which is able to encourage the
growth of plants and the economy of the natural realms? Since so much
utility is apparent, can the disadvantage that accrues to the human race
through one or other eruption, exempt us from the gratitude we owe to
Providence for all the measures it employs?
The reasons I have cited to encourage [such gratitude] are naturally
not of a kind to furnish the greatest conviction and certainty. However,
even suppositions are acceptable if the aim is to move mankind to a desire
for gratitude towards that supreme being that is worthy of respect and
love even when it chastises [us].
note.
I mentioned above that earthquakes force sulphurous exhalations
through Earth’s cavities. The latest information from the mining shafts
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in the mountains of Saxony confirms this by means of a new example.
They are now so full of sulphurous vapours that the workers have had
to abandon them. The occurrence at Tuam in Ireland, when a shining
atmospheric phenomenon appeared in the shape of pennants and flags
over the sea, changed colour gradually, and finally spread a bright light,
whereupon a violent earth tremor ensued, is a new confirmation of this.
The change of colour from the darkest blue to red and finally into a
bright white light can be attributed to the exhalation that was initially
very thin when it erupted and then gradually increased by the more frequent influx of further vapours; as is well known to science, these vapours
must go through all degrees of light from blue to red and finally to a shining white. All this occurred before the tremor. It was also proof that the
seat of the conflagration was at the bottom of the sea, as the earthquake
itself was mainly felt on the coast.
If one were to extend the list of places on the Earth that have always
experienced the most frequent and most violent tremors, one might add
that the western coasts have always suffered far more incidents than the
eastern coasts. In Italy, Portugal, in South America, and even recently in
Ireland, experience has confirmed this correspondence. Peru, which is
situated on the western coast of the New World has almost daily tremors,
while Brazil, which has the Atlantic Ocean to its east, experiences nothing
of this. If one were to conclude any causes from this curious analogy,
then one might well forgive one Gautier,21 a painter, when he seeks
the cause of all earthquakes in the rays of the sun, the source of his
colours and his art, and imagines that it is precisely these that drive our
great sphere around from west to east by striking the western coasts
more strongly, which is allegedly the reason why those coasts are upset
by so many tremors. In a healthy natural science, however, such an idea
scarcely merits refutation. The reason for this law seems to me to be
connected with another one, for which there is no sufficient explanation
as yet: namely that the western and southern coasts of nearly all countries
are steeper than the eastern and northern coasts, which is confirmed by
a glance at the map as well as the reports of Dampier,22 who, on all his
maritime journeys found this to be almost universal. If one derives the
depressions on dry land from subsidences, then in the regions with the
greatest declivity, deeper and more numerous caves must be encountered
than in places where the Earth’s crust has only a gentle slope. But this
has a natural connection with earthquakes, as we saw above.
concluding observation.
The sight of so many wretched people as the latest catastrophe caused
among our fellow citizens ought to arouse our philanthropy and make
us feel some of the misfortune that afflicted them with such cruelty. But
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History and description of the earthquake of 1755
we go against this very much if we always regard this sort of destiny as
a punishment meted out, which afflicts the destroyed cities on account
of their evil deeds, and if we regard these unfortunates as the target of
God’s vengeance over whom his justice pours out all its wrath. This
kind of judgement is a culpable impertinence that arrogates to itself
the ability to understand the intentions behind divine decisions and to
interpret them according to its own opinions.
Man is so opinionated that he sees only himself as the object of God’s
activities, just as if the latter had only him to take account of in devising
the appropriate measures for the ruling of the world. We know that
the whole essenceq of nature is a worthy object of divine wisdom and
its activities. We are a part of this and try to be all of it. The rules of
perfection in nature at large are regarded as irrelevant, and everything
is to be seen merely in relation to ourselves. All the things in the world
that provide comfort and pleasure, people imagine to be there only for
our sakes, and nature supposedly does not undertake any changes that
might be any sort of cause for discomfort for mankind except to punish
us, threaten us, or to wreak vengeance on us.
Nonetheless, we see that an infinite number of evildoers sleep in peace,
the earthquakes have shattered certain countries since time immemorial
with total indifference to the old and new inhabitants, that Christian
Peru is shaken just as much as the heathen part, and that many cities
have been spared this devastation from the beginning, cities that could
not presume to be any less punishable than others [that were destroyed].
Thus man is in the dark when he tries to guess the intentions that God
envisages in the ruling of the world. We are, however, in no doubt when
it is a question of applying these ways of providence in accordance with
its purpose. Man is not born to build everlasting dwellings on this stage
of vanity. Since his entire life has a far nobler aim, how well does this
harmonize with all the destruction fit into this which allows us to see the
transience of the world in even those things that seem to us the greatest
and most important and to remind us that the goods of this world cannot
provide any satisfaction for our desire for happiness!
I am in no way implying that man is subject to an unchanging fate
of natural laws without respect to his particular virtues.r That same
supreme wisdom from which the course of nature derives that accuracy
that requires no correction, has subordinated lower purposes to higher
ones, and in just those intentions in which the former has often made
the most significant exceptions to the general rules of nature in order
to attain those infinitely higher aims that far surpass all the resources
of nature, in those intentions the leaders of the human race will also
prescribe laws in their government of the world to regulate even the
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course of natural things. When a city or country perceives the disaster
with which divine providence terrifies it or its neighbours, can there
be any doubt as to the party it should support in order to prevent the
threatened destruction, and will the signs still be ambiguous that make
those comprehensible intentions to whose implementation all the paths
of providence unanimously either invite or drive mankind?
A prince who, activated by a noble heart, allows himself to be moved by
these hardships of the human race to avert the miseries of war from those
who are threatened on all sides by serious misfortune, is a beneficent tool
in the gracious hand of God, and a divine gift to the peoples of the earth
who can never assess its worth in keeping with its magnitude.
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8
Continued observations on the earthquakes
that have been experienced for some time
editor’s introduction
Kant’s third and final essay on earthquakes was published in the 10 and
17 April issues of the Wöchentliche Königsbergische Frag- und AnzeigungsNachrichten and continues the reflections presented in the previous two
essays. Kant’s primary concern in this essay is to refute various competing opinions about earthquakes, specifically, those by Gottfried Profe
and Pierre Bouguer. His main objection to Profe, who claims that the
alignment of the planets was responsible for the Lisbon earthquake, and
to Bouguer, who agrees with an unnamed Peruvian author that the Moon
could bear some responsibility for this event, is that if one calculates the
actual gravitational effect that either the planets, fully aligned, or the
Moon by itself would have, the effect would be minuscule and certainly
much too small to be a significant cause of such a large effect. Moreover,
Kant notes, a report by Gassendi suggested that a rare conjunction of the
three outer planets, which had occurred in 1604, resulted in no significant earthquakes, thus contradicting Profe’s theory. Kant concludes his
treatment of earthquakes with a brief reiteration of the main contours
of his theory.
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Continued Observations
on the
Earthquakes
that have been experienced for some time.
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The fire of the subterranean vaults has not yet subsided. The tremors
continued until recently and terrified countries where this evil was previously unknown. The disorder in the atmosphere has altered the seasons
in half of the world. Those who know least claim to have guessed the
cause. Some can be heard to declare without reflection or understanding
that the Earth has shifted its position and come closer to the Sun by I
don’t know how many degrees; a judgement worthy of a Kindermann,1
were he to arise again to peddle the dreams of a deranged mind as observations. In the same category are those who bring comets back into play
since Whiston2 has taught even the philosophers to fear them. It is a
common extravagance to import the source of an evil from several thousand miles away when it can be found in the neighbourhood. This is what
the Turks do with the plague; this is what people did with the locusts,
with the livestock disease, and with God only knows what other evils.
People are reluctant to perceive something that is merely close at hand.
To detect causes at an infinite distance is the only proper proof of an
astute understanding.
Among all the conjectures that, by differing significantly from the
rules of proper science, can easily deceive people who do not know how
to test them, is the notion attributed in the press to Herr Professor Profe
of Altona.3 It is admittedly a long time since the observation of major
events on Earth caused suspicion to be thrown on the planets. The lists
of harsh accusations our revered ancestors, the astrologers, have made
against these bodies have been filed in the archive of antiquated fantasies
along with the true story of fairies, the sympathetic miracles of Digby4
and Vallemont,5 and the nocturnal events on the Blocksberg.6 But since
natural science has been purged of these foolish ideas, a Newton has
discovered and confirmed empirically a real force which even the most
distant planets exercise on each other and on our Earth. However, to
the great misfortune of those who wish to make extravagant use of this
noteworthy property, the magnitude of this force and the manner of its
operation are defined, with the assistance of geometry, by the very same
observation[s] to which we owe its [original] discovery. Now no one can
any longer make us believe whatever they like about its effects. We have
the balance in our hand by which we can weigh up the effects against the
given cause.
If someone, who had been told that the Moon attracts the waters of the
Earth and in this way causes that rising and falling of the ocean that we
call the tides, and further that all the planets are endowed with a similar
gravitational force, and, when they are close to a straight line drawn
through the Earth and the Sun7 combine their gravitational forces with
that of the Moon, if, I say, such a person, with no ambition to examine the
matter more closely, were to suppose that these combined forces were
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Continued observations on the earthquakes
able not only to bring the waters on the Earth into the violents motion we
observed on 1 November, but also to ignite the hidden tinder by means
of some influence on the subterranean air so as to cause an earthquake,
then no more can be asked of such a person. But one expects more from
a student of nature.t It is not sufficient to have stumbled upon a cause
that has some similarity with the effect; it must also be proportional in
its magnitude. I shall quote an example. Dr Lister,8 an otherwise able
member of the Royal Society of London, had observed that the marine
plant called sea lentil has an unusually strong scent. He noticed that it
is frequently found on the tropical coasts. Now, since a strong scent can
probably move the air a little, he concluded that the prevailing east wind
that blows constantly in these seas and extends more than a thousand
miles from the land, stems from this cause, especially since this plant
turns with the Sun. The absurdity of this opinion is simply that the cause
is out of all proportion to the effect. The same applies to the force of the
planets when compared to the effect that is supposed to derive from it,
namely that of moving the seas and causing earthquakes. Perhaps people
will say: do we know the strength of the force with which these celestial
bodies can act upon the Earth? I shall reply to this question shortly.
Herr Bouguer,9 a celebrated member of the French Academy, relates
that during his stay in Peru, a learned man who wished to become Professor of Mathematics at the University of Lima had written a book
entitled An Astronomical Clock of Earthquakes, in which he undertook to
predict earthquakes from the orbit of the Moon. It is easy to guess that
it is all very well for a prophet in Peru to predict earthquakes, as they
occur there almost daily and differ only in their strength. Herr Bouguer
adds that anyone who, without much thought, bandies about ideas concerning the rising and falling node of the Moon, proximity and distance
to the Earth, conjunction and opposition, might happen at times to say
something that is confirmed by events, and he [Bouguer] admits that
he [the Peruvian author] has not always predicted incorrectly. He himself conjectures that it is not altogether unlikely that the Moon, which
moves the waters of the ocean so strongly, may have some influence on
earthquakes, either by carrying the water, which it raises to extraordinary
levels, into cracks in the Earth that it would otherwise not reach, and that
this causes the raging motion in the deep caves, or by some other kind of
connection.
If one considers that the gravitational forces of the celestial bodies
can act on the innermost parts of matter and thus move the air in the
deepest and most inaccessible passages of the Earth, then one can hardly
deny the Moon some influence on earthquakes. But this force would at
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most merely stimulate the flammable matter within the Earth, and the
remainder, the tremors, the motion of the water, will only be an effect
of this latter.
If one ascends from the Moon to the sphere of the planets, this capacity
gradually disappears as the distances increase, and the combined forcesu
of all the planets produce only an infinitely small fraction of the effect
produced by the single Moon which is so close to us.
Newton, who discovered the admirable law of gravity, which must
be regarded as the most fortunate attempt the human intellect has yet
made in understanding nature, teaches us how to calculate the gravitational force of the planets that have moons around them and he has
established that of Jupiter, the largest of all the planets, to be somewhat
less than one thousandth part of the gravitational pull of the Sun. The
ability to bring about changes on our Earth through this force decreases
in inverse proportion to the cube10 of the distance and is thus, in the
case of Jupiter, which is more than five times further from the Earth
than is the Sun, and if one takes the ratio of its gravitational force into
account, 130,000 times smaller than what the gravitational force of the
Sun alone can effect on our Earth. Now, on the other hand, the attraction of the Sun can raise the level of the water in the ocean by about
two feet, as we know from experience combined with calculations; thus
the attraction of Jupiter, when combined with that of the Sun, would
add one 65th of a decimal scruple11 to this level, which would amount
to approximately one thirtieth of a hair’s breadth. If one considers that
Mars and Venus are much smaller bodies than Jupiter and that their
gravitational forces are proportional to their masses,v then one is still
going too far if one attributes to both together approximately twice as
much capacity to affect our Earth by their gravity as Jupiter, because
they are roughly three times closer, even though they have many hundred times less bodily content and hence gravitational force. But even
if I were generous enough to make their force ten times greater, they
could not, even combined, raise the level of the sea water by one third of
a hair’s breadth. If one adds the remaining planets, Mercury and Saturn,
and considers them all in conjunction, then it becomes clear that they
could not nearly increase the rise in the water brought about by the Sun
and the Moon together by one half of a hair’s breadth. Is it not ridiculous to fear frightening motions of water resulting from the attraction
of the Moon and the Sun, when the level to which they raise the water
has been increased by one half of a hair’s breadth, whereas without these
there would [supposedly] be no danger to worry about? All other circumstances completely contradict the alleged cause. Just as the Moon causes
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Continued observations on the earthquakes
the highest tides not merely at the moment when it is closest to the
[imaginary] straight line drawn through the Sun and the Earth, but does
so for some days before and afterwards, so also the combined [force of
the] planets should have caused motions of water and earthquakes on
several successive days and for several hours at each of them, if they had
had any part in it.
I must beg my readers’ pardon for having led them so far around
the firmament to enable them to judge correctly events that have taken
place on our Earth. The effort one applies to stop up the sources of
errors also provides us with purified cognition. In the following piece,
I shall consider the most noteworthy appearances of the great natural
event that have occurred since those which I attempted to explain in a
separate article.
The planets have been acquitted before the tribunal of reason of having
had any part in the devastation that befalls us in earthquakes. From now
on let no one suspect them again in this connection. There have probably been several planets in conjunction on previous occasions without
any earthquake being felt. According to Gassendi,12 in 1604 Peiresc13
observed the rare conjunction of the three outer planets, which occurs
only once every eight hundred years, but the Earth remained safe. If
the Moon, upon which alone such suspicion might fall with some plausibility, did have a part in it, then the contributing causes would have
to be present in such full measure that even the smallest external influence could provide the impetus for the change. For the Moon frequently
comes into the position in which it exercises a maximum effect on the
surface of the Earth, but it does not produce earthquakes nearly so often.
The quake of 1 November occurred soon after the last quarter, but at
that time the Moon’s influence is at a minimum, as Newton’s theory
and observation show. Let us therefore look for the cause in our place
of habitation itself, for we have the cause beneath our feet.
Since the earthquakes mentioned previously, none have occurred that
have extended further afield than that of 18 February. This was felt
in France, England, Germany, and the Netherlands. As reported from
numerous places such as Westphalia and the regions of Hanover and
Magdeburg, it was also more like a gentle rocking of ground moved
by violent subterranean storms than the explosions of burning material.
Only those in the top floors of buildings felt the rocking; it was hardly
noticed on the ground below. Already on the preceding 13th and 14th,
tremors were felt in the Netherlands and neighbouring places, and on
those days, especially from the 16th to the 18th, widespread hurricanes
raged in Germany, Poland, and England, and lightning and tempests
occurred; in short, the atmosphere had been brought into a kind of
fermentation, which may serve to confirm what we have already noted
elsewhere, namely that earthquakes or the subterranean conflagrations
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that are their cause, alter our atmosphere by injecting foreign vapours
into it.
From time to time subsidences have occurred in the soil. Pieces of rock
have broken loose from the mountains and have rolled into the valleys
with terrible force. Besides, such events often take place without any preceding earthquakes. Continuous rain often causes the channels supplying
the wells,w filled with water, to undermine the base of an area of land by
washing out the soil, and likewise to tear pieces of rock from the tops of
mountains, especially when the effects of frost and water are combined.
The great crevasses and clefts that have opened up and usually closed over
again in Switzerland and other places are clearer proofs of an expansive
subterranean powerx as a result of which the layers of somewhat lesser
density have fractured. If we consider this fragility of the ground we stand
on, the store of subterranean heat that might everywhere maintain the
combustible materials, seams of coal, resins and sulphur in a constantly
blazing fire (just as coal mines, when they have ignited spontaneously in
the air, will often smoulder and burn outwards for centuries), if, I say,
we consider this constitution of the subterranean caverns, would not a
[mere] nod be enough to plunge our vaults into whole seas of glowing
sulphur and to devastate our inhabited places with streams of burning
material, just as the ejected lava destroyed the villages that were built
at the foot of Mount Etna in undisturbed tranquillity? Herr Dr Poll
is right, when, in a short treatise on earthquakes, he demands nothing
more than water to set the ever-glowing embers beneath the earth in
motion by means of expanding water vapours and cause the earth to
tremble; when, however, he tries to invalidate Lémery’s experiment14
(which explains the tremors by adding water to a mixture of sulphur and
iron filings) by saying that no pure iron is encountered in the earth but
only iron ore, which does not produce the required result in this experiment, then I would ask him to consider whether the manifold cause
of the heating, e.g., the weathering of iron pyrites, the fermentations
through the admixture of water, as is detected in ejected lava after rain
and likewise in the permanent fire of Pietra Mala, after it has melted
the deep-seated iron ore to granulated iron, or even magnetite, which is
very like pure iron and which is doubtless to be encountered plentifully
in the depths, is not able to provide sufficient material for carrying out
this experiment on a large scale. The most curious observation reported
from Switzerland that a magnet, together with the thread from which it
was hanging, deviated several degrees from its vertical direction during
an earthquake, seems to confirm the involvement of magnetic materials
in earthquakes.
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Continued observations on the earthquakes
It would take a large volume to cite and examine all the hypotheses
that have been proposed in order to forge new paths of research, and
that often succeed each other like the waves of the sea. There is also
a certain good taste in the natural sciences which knows at once how
to distinguish the unbridled excesses of a craving for novelty from the
secure and careful judgements that have the evidence of experience and
of rational credibility on their side. Father Bina,15 and only recently
Herr Professor Krüger,16 have ascribed earthquakes and electricity to
the same causes. There is an even greater temerity in the suggestion of
Herr Prof. Hollmann,17 who, having demonstrated the usefulness of air
vents in soil ignited by inflamed materials by the example of volcanoes,
without which the Kingdoms of Naples and Sicily would no longer exist,
then maintains that the uppermost crust of the Earth ought to be dug
through, down into the deepest burning clefts, so as to provide a way
out for the fire. The great thickness, together with the hardness of the
interior layers, without which such cruel attacks of earthquakes would
have destroyed such a country long ago, and likewise the water that
soon puts an end to all digging operations, and finally the incapacity
of human beings, make this suggestion [no more than] a fine dream.
From the Prometheus of modern times, Herr Franklin,18 who sought
to disarm the thunder, to that man who sought to extinguish the fire
in Vulcan’s workshop, all such endeavours are proofs of the boldness of
man, allied with a capacity which stands in a very modest relationship
to it, and ultimately they lead him to the humbling reminder, which is
where he ought properly to start, that he is never anything more than a
human being.
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9
New notes to explain the theory of the
winds, in which, at the same time, he
invites attendance at his lectures
editor’s introduction
This set of notes was published on 25 April 1756 as part of Kant’s advertisement for the lectures he was planning to give at the university in the
summer semester of that year. For this reason, it is appropriate that at the
end of these notes he announced the textbooks that he would be using for
his lectures on physics, logic, and metaphysics. Kant used no textbook for
his lectures on physical geography, since none was approved to that end,
and he always used Wolff for mathematics, most likely Wolff ’s Auszug
aus den Anfangsgründe aller mathematischen Wissenschaften [Excerpt from
the First Principles of All Mathematical Sciences].1
Kant does not present a comprehensive theory of winds in this essay.
Instead, over the course of five notes, he attempts to explain a series of
specific meteorological phenomena, sometimes in novel ways. (In each
case, he cites independent experience to confirm the principle that is
central to each explanation.) Accordingly, he claims that the direction
of coastal winds – onshore or offshore – depends on the expansion and
contraction of air that is caused by differences in the rate of heating and
cooling of the land and the water at sea during the day and at night
(first and second notes). He also explains the difference in (east–west)
direction arising for winds moving from the Equator towards either of
the Poles and vice versa that is due to the rotation of the earth (third
note) – a phenomenon that was later described in terms of the Coriolis
effect– as well as the easterly direction of the trade winds (fourth note).
Finally, Kant provides an account of monsoon winds (fifth note).2
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