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. .. riilliLllÈ
trit'
THE CONTRIBUTION OF THE
MECHANICAL CLOCK TO THE
IMPROVEMENT OF NAVIGATION
Edoardo Proverbio
lstituto di Astìooomia e Fisica Superiore, Via Ospedale
Caglirri. tlaty
LATITUD! SAILING AND THE IIRST MECHANICAL CLOCKS AT
72
09100
SEA
The impÒrtancè of tine scale definition in nodern navigation is well knom (1). The
problen of tiùe keeping and deternination has in facÈ played an inportant role in rhe developmeùt of navigatiÒn since man began sailing Lhe ùcèaùs.
ln 1420 rhe Portúguese begaú their exploraÈion of the Atlantic and, for about one centuryr
up lo l{asellanrs circllnnavigation of the slobe (1519-1522), oceanic navigarion was pracrically
a Hispano-Portuguese monopoly. Mter the second half of the XVI century the discovery of neq
lands and ùavigaIiona1 routes was doninated by the comfrercial necessities of rvo new seafaring
coútries:
England and Holtand.
This great expansior in oceanic navigation vas in turn the cause óf an inporÈanr rechnological revolution in navigational methods and technigues uhich brought abour the change frm
prè-astronomical navigation, which wenr fron the Prehistoric period to rhe end of the Middle
AgesJ to so_calLed astrononical navigation. As is well-knom, this consists of establishing
the position of the shi! on thè basis of the deternination of the asÈrononicat coordinates:
latilude and longitrde. The first latitude obselvaÈions on the high seas were probably carried
out toirards the eùd of the Xv century (2). A new era in oceanic navigation began at Èhat tine
based on the tecbnique of lariLude sailine.
This teclniqúe is based on an estímation of the angular distance travelled ly the ship
from north to south or vice-versa by means of the neasurenent of the angìrlar height Òf the
North Star and thè Sun rith the úse of large astrolabes and sea-rlngs (3) and, later on,
sèxranrs. Having reached the Ìatirude of rhe point of arrival or landfal1, navigation
.ontinued by keeping this Iatitude fired and sailinS along it with the aid of azinuÈh compass
and l og,
ln latirude sailing it qas necessary to measure tine intervals to establlsh the speed
aùd tlie disÈance the ship had lravè11èd. Only vhen extra-meridian neasurencnts of the Sun's
helght vere carried our ruas it necessary to know the eract nonent in irhich this observation
ùas made. The nost comon way of finding the rime ar sea dùing the day in rhe M century
aas based on the ùse of the universal ring dial. At the end of the sane century it becane
!ossible lo deternine the tiúe even at nighc ùiÈh the use of the so-ca11ed "nocturnaI".
The keeping of line otherrisè was based on the use of sand-g1asses, preslúrably invented
in the Mediterranean area during the xII or XIII century and úsed for the neasurenent of time
intervals and the correspondine distance on a !ortolan or sea-chart (4).
95
E. ?rove
96
rb i o
The appearance of the mechanicaL clock tovards the end of the XIII century was the
expression of the importanÈ technological rèvolutión going on at that time. This is not the
place for a discussion of the invention of the nechanical clock and its escaperent nechanisn,
knom as the verge-and foliol, the origin of vhich is nol coúplet€ly c1ear, (5), but it úúst
be said that in the XV century the mechanical clock was ridely used for tiúe keeping on land
in a whole series of activiries.
A,Ìong lhe reasons which kepl nechanical clocks fron being
of finding an adequate technical
used in navigation, there was certainly the difficulty
solution to the probLen of the clock's srlspension so as tó avoid oalfunctioning or stolpage
becausè of rough seas.
The póssibility
of researching the role played by the oechanical clock in sailing at this
tine and for the improvenent of navigation is made quite difficúlt by the lack of reliable
docuents. If, as seens to be che caser English ships did not use nechanical clocks on board
unÈil the xvII century, ir is certain that on Dutch ships thesè úere used starting from the
end of the XVt century. The úse of new tiae-keeping technologies by the Dutch is not
surprising if it is kèpt in nind that fror the niddle of the XVI century aúd fÒr the nett
hundred years rhey motropolized oceanic navigatiÒn aùd che scar{,h for ne! comne!.,ial roures.
The only docment we have on the use of the mechanical clock 3t sea concerns its use by
I,ii1len Barentsz, a whaler and well-knom ex?lorer, during the ea!edition irhich began in 1596
in the search for the Norlh-East passage and now conser?ed in ehe Rijksnusem of Arìsterdam (6).
The use of the nechanical clock wíth the balance wheel at sea was dependent on its
intrinslc
precision and the use to which it was put.
Regarding precision, the kind of clock vith an hour hand used by Barentsz could caúse
an error of about 5 to l0 ninures per day. hecision was greatly inproved in the second haÌf
of the XVII cenÈury with the introduction of the dial plate indicating the ninùtes. U! to this
time lt is probable that the mechanical clock was used exclusively as standard shilboard tinèkeeper beside the sand-glass. The irportance of the use of the nechanical clock as a linekeeper at sea 1{as greatly accenruated by the introduction of nethods of astrononical longitude
THE FINDING OF LONGITUDE AT SEA BY ASTRONOMICAI- MEîHODS
As has been seen, during the XVI century longitude was stil1 estimated by dead reckoning,
a nost inaccurate nethod becaùse of uncertainty in neasurenents caused by breezes, tides and
currents. As Nevil uaskelyne mote in the prerace to ]nis Eritísh Mariner's Gu'íde ir 1163
referring to this nethod: I'Five, ten or evèn fifteen degrèes are errors which nÒ óne can be
sure he nay not fa1l into in the course of a long voyage"
only after the use of the telescope in 1609 by Galileo (1564-1642) were sone astroùonical
nethods proposed and used for longitude determination. As longitude can be found only by
Eeasuring the difference at the sane mooedt betreen Èhe 1ocal tine of the ship and the Local
tine of longitúde zero or prime neridians, it vas thought that the observation of celestial
lhenomena
visible
over a large part of the Earth's surface could resolve the !robÌen.
based on the observation of the eclilses
The praclical mèthod proposed by Galileo
'as
of Jupiter's satellites, vhich he had discovered in January 1610. This method' as Galileo
hinseÌf stated, requlred, "first of all a precise knowledge of the movenents of Jupiter's
satellites and the definition snd distribution of the ephemerides of the instants of the
eclipses in the tifle of the first meridian. Secondly the building and use of tèlescoles of
The Contribution of the vechanical Clock
such perfection as to nake clearly visible and observable the phenomena of the eclipses.
Thirdly the discovery of artifices capable of overconing the problems deriving Iroú the shi!'s
novernent \rhi1e using the telescole.
And finally the realization of a very precise clock to
numbér the hours and Èhe fractions of the hours.rr (7). As can be seen, Galileo's ?rojecE eas
an attenpt to find an overall solution to longitude detèrmination at sea. To makè Lhèse
proposals operative in fact, he sùggesÈed solutions he felt vere practicable (8). In
particular, as regards Ehe "measúrer of tine", based on the oscillations of a pendulun of his
invention accurately described in the lerter to Lorenzo Reaglio dated 15 June 1617 and in other
letters and pubÌications (9), it is a pity calileo was not able to realize his "nisuratore
de1 teùlpo'r for longitude detennination at sea. Galileo attributed unusual !recision lo this
"tine-neasurer", more than one order of nagnitùde greater than comon nèchanical clocks óf
the epoch (10). A kind of manual for the construction and use of such a rrtime
published in Paris in 1639, probably by uersenne, tnder the title:
L'usalle du catuan de
Lthorlage phV s í.118 1míùet'elle lar calilée, Mathematicien du Dùc de llorence.
próposals for soÌving the problem of lonaitude detÈrminatión by
observation of the ecli!ses of Jupiter's satellites, made first to the King of Spain and later
to the Netherlands, met vith no success for various reasóns (11), and only from about 1690
vere Galileo's methods for finding the longitude used rather extensively, but only on land
Thus, his lrolosal for the realization of a "time-neasurer" with a pendulm for the determinarioo of longirude at sea remained on the draving board.
As is knom, calileo's
In 1514, Johano Weroer (1486-1522), in his edition of PÈolemyrs Ceognp4 (1?) ]nad
suggested another astronomical nethod for the finding of longitude based on the reasurement
of the distance betveen the moon and the fixed sÈars, inclùding the sun (13). This nethod
involved neasuring the angúIar distance beÈween the moon and the srú or stars with a cross
staff and successively a reflecting quadraot and sextant, and predicting, by calcùlation, the
tines, in relation to the prine neridian, when the noon vould be at the angular distance from
the star as seen fron the ship.
Anerigo Veslucci had already observed that "the lighter coúrse of the moonrr among the
stars coúId be used in longitude delernination at sea (14). However, the difficully
of
knowing the móon's position in advance ùich great accuracy and the comllexity of the teduction
calculations contributed to its úse being discouraged in navigation, aE least until the
beginning of the XVIII century. This explains the failure of altemlts made in the early part
of the XVII century (1637) by Joho Baptist Morin (1603 1656), when he proposed to the King
of France the preparation of lr.rnar tables corrected for refrac!ion and horizontal parallax in
vieR of mking lunar observation available fÒr the deternination of longitúde at sea.
The only oavigator at the beginning of the XVII ceútùry vho used a nethod based on the
noon's notion for lonsitude determination at sea appears to bè Villiam Baffin (1584-1622)
in using nethods based on lunar motion
during his voyage to creenland (15), The difficulty
dèrives not only from the inaccuracy of lunar lablès, but also fron the inadequacy of the
nechanical ctocks and sand-glasses used on board for tine keeping during the day. rhe
sitúation induced nóst invèstigators to considèr the possibility of lroviding a more córrect
It is interestlng to observe that together vith the vaÌious atcempts ro better the
performance of the clocks used in longitude deternination, a great effort vas nade to inprove
knowledge of lunar notion in ordèr to solve the 1Òngitude problem at sea. These efforts led
to positive results thanks to the fact that three events of revolutionary irnportance took !lace
simultaneously in the second half of the XVII century:
9l
98
n. Proverbio
i) first of alt the creation of scientific organlzations such as the Royal Society (j662)
and the Acadénie des Sciences (1666) and of insritúrions for astronÒmica1 research such as
che astrononical observatories of ?aris (1667) and creenvich (1675) which creared the operative
bases for tackling the problen of longirude dererninarion a! sea. The Royal Observarory at
Greenvich had been founded qith a clear mandaÈe to rectif)i "the table of Èhe notions of the
heavens, and the places of the fixed stars, so as ro lind out the so nuch desired longirude
of places for the perfecring of the art of navigation"i
ii) secondly, thanks to the contribution of a great núber of astronoùers, ùarhematicians
and physicists the grounds were laid for rhe research, ahich culminared Firh the publicarion
of Nertonrs Ptí|cípad, Ìèading to the discovery of rhe physicat laws of motion, wbose applicaLión to the motior of the heavenly bodies and clockwork movenènr alloved the solurion of a
whole series of theoretical and pracrical problens- Ir musr nor be forgotren thar,'rhe invest
j-salion of timekeepers for Lh. longitùde was s!bordinarc r.r an even Larg]:,r projecr Laun{iÌred
and carried Lorward by the samc grotrp of ùen! that df constructing a cheory ot Lhc lars Òf
mo!ion and establishing th! Copernican rheory úpon a súr. foundarion o[ ùechani.s" (]6)i
iii) finalry, the foundations rere laid for Lhar important rechùologic!t revoturioù whi.h,
Hith the definirioù of ncw technoLogicaL.apàciries and {:ompeLe.ce and rh€ Émèrgctrce ot a nèù
prolessional class of technicians in the field of o?tics, echanics and chronoùerry, 1èd ro
the realization of nev and more lrecise instrunents for the seasuremen! of tine and angles,
with the appÌication of rhe relescope to rhe sraduated insrrwen!s.
Here it can only be mentioned in passing thar John Falmsteed, rhe firsr AsLronomer RoyaÌ,
and his successorsr not only Nerè cÒn!inced of the impractabiÌiry of finding the longitude
by any method but Èhat derived fron a perfecr knovledge of rhe moonÌs ùórion, bur also rorkéd
or the problen of the moon's motion, rith rhè purpose of iú?rovirg rhe accuracy required for
a satisfactory lunar Èheory (17). lr úas noÈ by accident rhar rhe ships of the ltast India
Conpany vere èquipped regularly irith ùarine clocks only from about 1770 onwards (j8).
THE ROLE
OI
THE I{ECIIANICA], CLOCK
IN
LONCITIDE DITER}JINATION AT SEA
Experimentation with the pendulN as a timekeeper began in England, Hó1land and ]raÌy
at about the sane tine, sEinúlated by Ricciolirs recohmendarion of its applicarion in his
Alnagesl,un of 1651 (19), and greatly influenced by Calileo's !róposals as úe11 as Mersenoers
sLudy on pendulm isochronism (20). However, ve do oot knov if the first atrempts following
this tÒ apply the pendulm ro mechanical clocks, both reighted and wirh springs, for longirude
deterninaÈion at sea, Fere made in rhe hopes of consrrucring rinckeepèrs to be used for keeping
time day by day, thaÈ is,
of oeasuriog longirude by tùnar disrance, or it rhè
intention was rhat of realizinA acrual Íarinè clocks to be used for the keepioA of rhe tine
zcro neridian on deep sea ships during long voyages.
The idea of detemining longirude differences by transporring rinepieces goes back, as is
kno\r!, ro ceM Frisius, who expounded ir in 1530 in his book re ptinc.í.pia Astrancniae et
Co€nalfcphade (22), even though in l5l0 Alonso de Sanra Cruz had lrolosed the sa e merhod for
lonAitude deterniDation at sèa (23). The inveúrion of rhe fusée, abou[ 1525) ccrrainly
contribúted to nourishing the belief that rhe neú inproved portable rimepieces vorld be capable
of giving nore or less úifom time duing twenty-four hours also ar sea.
The fact renains that until halfvay rhrough rhe XVII cèntury no real cha.ge vas inrróduced
into the nethods of astrononical navigarion for rhe derermination of longirude.
It is possiblè, starting from this period, to sing:Le óur rhree distinct phases in rhe
developnent of a mechanlcal clock intended for marine use. In Èhe firsr lhase, which began
Tte Contribution of the l4echanical Clock
aboùt 1660 and fiúished in lhe leriod from 1675 to 1680, it is difficult
to establish from
the technical !óint of vieù iust lhat differences there qère betùeen normal pendulm clocks
and those ezplicltly designed for longitude determination at sea.
fron the description of the first pendullft clocks ]n the Ilarolagi.tnn constructed by Sanuè1
Coster stàrting from 1657, it is cvident that the goal of Eùygens vas that of realizing a
lrecise tinekeeper for asEronotuical purposes rather than for longitude determination, even
thoùgh in maDuscript K, vritten betùeen 1656 and 1651 (24), Huygens quotes the Geogy.ÌpbJ af
Metius vith reference to the longitude problea. This fàct brought about aD objective dela)'
in the realization of marine clocks capablè of competing with longitude determination
tecÌDiqúes based on the measurenent óf lunar dislances. In effect, Òn1y fron 1661-62 can ve
daie the adaptation of tao of Huygèn's clocks by Alerander Bruce for the precise lurlose of
delemining lonsitude at sea (25). The story of these tro clocks is reported in detaiÌ by
Drmond Robertson (26). 1t is inÈerèsÈing lo observe that these two clocks, driven by a
spring like Coster's first clocks, differ fron these and from the clock described in Hor'ÒLogiln
in 1658 because of the different suspensión óf the !endùlM betveen the cycloidal cheeks, sith
its rod held het\ièen tvo jaws in a s?ecial crutch in order to prevent a rotary notion of the
lendúlun at sea. The performauce of these clocks at sea, Lested dùring a voyage to london
undertaken by Brùce himself in 1662, aìid Ìater during a voyase to Lisbon in 1663 in the charge
of Captain, Ìater Àdmiral Robert Holnes, was nol completely satisfaclory (27).
Better resul!s seem to have been given by these clocks during the tests rhèy under\,rent
durinB the voyases betveen Africa and America by captain Holnes in 1665-66 (28). Relative
variations even of several minútes (3 to 7) were noted at the end of the voyages (29). Daily
delays on the order of one minute were reported by de la Voye in longitude deterninations at
sea betireeo Toulon and crete (30). These alternatins results inflùenced the opinion of Huygens
hinsèlf as regards the possibllity of using frechanical pendrlún cÌocks in longitude deternination at sea. So, in November 1663, he wrole lo Moray that I'clocks will never Aive longitude
with the greaLèst perfèctión even thoúgh they will always be of great hel! as their use is
perfectedr', ehile in February 1ó64, after havine desisned his "remontoirerr device, licensed
in Holland in Decènber 1664, he Mote sonething qúite different iD his letter to Johan de l,litt
(31). Scepticisn on the possibility of the use of ùechanical clocks ln the period fron 1670
to 1675 was also clearly expressed by ciovanni Hevelius. ln h,is Machina Coe1.est'is (1613) he
wróte: "Sone nourished the hope of finally discovering the distances from the meridians and
tlie exact longitude of places with the help of these pendú1m clocks: Uith this systèo thè
calculaÈion
oìrt, in ny opinion, according to \rha È is expected, especially on these
very long voyages lasting seveîal months" (32).
The fact renains that even after hís moving to Paris in 1666 and experinents on Dutch
aúd French ships the perfornance of lhe clocLs of Huygens, still
of rhe type tested by Brùce,
thc voyage fron Toulon to Crete in 1669 an error of about two
degrees, corresponding to about eight ninutes in tine, was noted (33).
showèd
no irprovenent.
On
The history of the narine clock proposed by Bruce and Huygens is quite interesÈing and
ís closcly connected sjrh that oi cLocks designed for the sÒLutioo of the Lo.tiiude probLèn
in lnsland and Italy in the saúe leriod.
The recent history of chrononetry has pointed úp rhe fact that the period fron 165ó to
1660 was crucial in Ehe developmenl of the nechanical clock and, in this period, perhaps even
lefore coster's clocks, in Switzerland, cernany, France and Italy lendul@ clocks with special
characÈerisÈics, like the clocks rith the escalenent at the bottoù and the horizontal crom\iheeI dorùvards, built in Rone and FÌorence (34), were being designèd and prÒduced.
99
ln the
vay we are of thc opinion that in che follo\,'ine period rhar idea of producing
and realized, indépendently, èven outsi.le EÒ1land. Already in
1660 Giuseppe canpani, in hts Li:scarsa 1:rtorna ai suai nuti a!íualí, declared thar hè had
invented a clock of great !recision, and huch nórè !erfect than the peùdulum regutator, for
determiring longitúde at sea. He did nor discuss this new rype of c1ock, bur it is knóm Ehar
for several years he carried out experinreflts on chis proiect (35). Some ye.rrs 1arer, in 1662,
Giuselpe's eÌder brothèr Ìlatteo pubÌished hts lÌuara ir.tenzicne dtÒtar.alí gírlsi,1:Esíni ad uEo
delle natígdziorc, reprinted the next year (36), in vhich for rhe firsr tine ve have the
presentation of a pendulm clock inside a glass belÌ to prorect it froo rhe effects of arnÒs?heric pressurc and sulp1ied with a double conpensatory s)'steri foi rhe neútraÌizarion o{ the
shiprs pitchiùg and rolling (37). In the period froù Ì658 ro 1660 in England Robert Hooke
carried out his abortive project for patenting and markering warches. AllhouAh in this coúntry
the first investigaÈions of tirekeeters for longirude deternination lras subordiDare, ',ro ao
even largLìr proje.t, that of constrùcting a general Lheor)' of [hÉ laws of norionrr (38), rhere
is no dÒubt that these activities qere the basis for the larer !Ìacrical coDtributions made
by Brucè and Llooke to the reà1izaÈion of marioe clocks.
same
marine clocks \ras cullivated
THE BIRTH
OI'TIE
TIARINE TII.IEKEE?ER
Until about 1675, the rèsutts of the use
úavigation were discÒuraging. No change took
afer the introduction of Feight-driven clÒ.ks
and enploled during the expedilion io 1669 ro
of oechanical clocks by Bruce and Huygens iú
place iú this situation, as has been
with a nine-inch pendìrÌun deviséd by Huyeetrs
expel the Túrks from Crere (39).
Things did not chanse aftèr the uncerrain ùse at sea of the neù clock wirhoút the Lirrle
chaiù, the so-cal1ed clock à remontoire, builr by Thúrer in Paris fron 1665 onwards (40), and
of the rriangùlar lendúlum.lock drivèn by a spring, designed in the period îran 1611 ta 1612
(41) but úsed at sea only duriDg the two voyages to the Cap€ of Cóod lÌope by Thonas ttelder
and Jo. de Graef in 1686-87 aDd and 1690-92 (42). on this latter voyage the difference in
longitude beÈreen tÌre Cape and Santiagó calculated vith tlie clocks on board was incorrccr by
more than six degrees (43). lle do not know if [he discovery by HuyAeDs of rhe general
conditions for isochronisn of the s?rings after rhe publicatiÒr aî tl\e EotÒLag.im aEc illetari.u.n
in 1673 is boudd up with Èhe idea of iúpróvinA [he pèrfornànce of the Mrine clocks.
Roberr Hóoke had already discovered that thÉ spring iras a "tautochrone't before 1666 and
made the first ap?Iication of a spring to a narine timekeeper in 1675 (44), the sane year in
which HuyAens nade lìis discovery kùom (45,46). lr is probabL. thrL thè spiraL spring
balance was applied to sone marine clocks soaetime about 1683 (47), and in any case nor beforè
1679, to judge from a 1eÈter by iluygens tó Paul Pellissón in lhich he srates thar "rhe lasr
trials with pendulu clocks at sea have not been whÒlly unsuccessful, burJ as they necessarily
suffèr fron the notion of a vesset, there is nore hope of success vith balance \rirh a slira1
sprins, etc. r'(48) .
Neverthè1ess thè adding of a spiral
Hùygens
s!ring to the osciltating balance Nheel in 1675 by
did not yield lhe resuÌts that he e:?ected, principally on a.count of rhe inflúence
of temperature (49).
The unreliability
oÎ the first spiral spring limekeepers and the 1ow esteem displayed by
Huygens for lhis kind of cIock, denìonstrated b), the fact that he hínself discarded rhe idea
first put forward in 1665 by Hooke on the possibility of applyins a spring regula.or (50),
ins!ired Húygens to re-exanine ner ty!es of narine !endúlum clocks. The projecr of the
"pendul!Í cylindric@ trichordonrr (51), whose tÒrsiÒoa1 oscilÌations were shom by Hùysens
The Contribution óf the
èchanical Clock
101
to be aÌnosc isochrone, ìrears thc date l683 But ehe realization of isochronoús marine cLocks
proved to be nost ùncertain cven lhough it seéms that tNo of these
clocks vere bùi1t by rhe fanous Dútch clocknaker Jóhanúes Van Ceulen (52). In 1683, however,
Huygens, ariting to Fullerius states lhàt "at the reguest of the (EasE Indies) ConPanv, he had
úndertaken the construction of clocks to deternine the longítude, possessing as constant e
regularity as those with the three-foot Pendulun, bùt such as should rot be disturbed bv the
based on this princi!le
notion of the sea" (53).
lron 1675-80 to 1710-15, a second Phase in the dévelópúent of marine clocks cen be singled
oìrt. This is a stage of meditalion on rhe Precarious sÈate of narine timekeèper technologv
ro'l"ui é n- previou oha' h4 "". , r"o o " rert.:i op, rl,r .
poor in results and innovations in narine clocks but one in
It is a phase larticùlarly
which the great, decisive steps in the aPPlication of chrononetry to astronomical navígation
Èhat viII take ?1ace in the first half of the XVIII century are being prepared. In this Period
we have the !rojects nuygens elaborated frofl 1693 onoards but already singled oút ten vears
before (54), for the realization of a "baÌancier narine parfait" (55) together vilh other
devices for ifrproviDg the accuracy of narine clocks (56). ln ?articúlar' Iluvgèns' attentioD
is focusèd on the ?roblem of the train friction and thc equilibritùî of the balance lrheel, on
qhich his successots aiIÌ concentrate their efforts.
These successÒrs .ti.l not overlook the fùndamèntaÌ inPortance of the esca!ement in
ia!roving tlre perfornìance of timekeelers. Thèy used esca!emenLs differeol fron the lraditional
crom-wheel escapement always used by Hùygens, sùch as the anchor escaPement invented bv Hooke
and introduced by William Clenent about 1680, or the "dead_beat" escaperìent devised bv George
craham about 1719 20.
About 1715, the tine Fas tipÉ for the finàI phase iD the realization of a narine clock
capable of resÒlving the problen of longiEùde delernination at sea. Ar rhe €nd of this third
phase it was decided to aban.lon ùnce and for all the lunar distances nethod for the finding
But
of longitude at sea, which had been ulhe1d by the Greenoich astroììomers i! Particular.
clocks
reached
an
accùracv
1770,
vhen
narine
rhis did not take pÌace overniahr. ùlly about
of jìrst
keelers
the old
vessels
a fev seconds a day and súrpassed by one order of magnicude che accuracv of the tinesupplied lo navigators at the beginning of the IvIII cencury Fas it decided to abandÒn
methods of lotrgitù.le determinatíoD at sea aúd the ConPaniès regutarlv equiPPed their
with the nev chronometers. This took !lace betqee! 1770 and 1790 (57).
The coDditions that gúaranteed lhis trúc revolutíon were the dèvelopnent of technologv in
France and England in the first half of the XVIII cenlury and economicaL íncentive. This
favoted by lhe "Act for Providing pubric reFard for such person
latter conditiod tas initially
or persons as shall discover lhe longitúdè at sea", Passed by the llitish Parlianent in 1714
on the reconmendalion of a comissjon, of vhich lsaac Ne\rto! was a nenber. The airard was fixed
at 10,000, 15,000 and 20,000 pounds sEèr1ing
The prolagonists of this teclDotÒgica1 and horological revolulion aere Eenrv Sullv' James
HarrisoD, Ferdlnand Berthoud aúd Pierre le Roy With thém it can b€ said that the nodern ùarine
chrononeler ras born and a significant
steP forward made in the im!roleoent of astrononical
102
NOTES AND RNFERNNCES
1. Klepczynski, It. J.r Modern navigarion sysrems and rheir retaÈion to rinekeepine,
Praa. 1DLL, 0crober, 1983, 1293-98.
2. BarthoÌomeo Diaz at Èhe Cape of cood Hope in 1488, and Vasco de cama in the Bay of
Sainte-Hé1ène in 1497 certainly nade use oJ large asrrolabes for latirud€ derermin
àtion ar sea. (E. poùtle, Le. aoliítialr.1è
Ì.o nariqat.iÒl! artlatantq e .t, XV
.7:àdZÉ), Coimbra, 1969, 11-18.
3. Shirley, J. W., Iúprovemenr in rechniques of navigaÈion in ElizaberÌran EnsiandJ in
'.'1:!*p-!:I'.chr1ai.osa 3 socí(:L chanse',, Ed. p. sorlam, rekniska Íuse;r, siockholn,
1980, p.123.
4. Waters, D, W., The insrrunenral and asrronomicat soiurion to che problem of lonsiru.ìe
at sea in rhe eighreenrh cenruryJ in "tt,.1jrspa|t lecltnoio.J! I S).iat Chan!€;,
ap- eit. , p.t4l.
5. Price, D. J., The prehistory of rhe ctock, DíscarettJ, Aprir, 1956, p.j53-57j prov.:rbio, E.
"L'evo1úzione deAli srrmenri e de11e tecniche ler ta conservazione de1 refr!o,',
Gioln. di AstuonÒnia, 2, 1982, 133-44.
6. Ìlorpurgo,8., Er difficile darare ún oroloaio anri.o, ld Ct.:sridra, ), j95j,23-28.
Galileors proposal to rhe States ceneral of rhe Nerherlands, l5 Augusr 1636. tn: calileo
calilei,rr@ere", !'i rcnze, Xvr,
466,
8. A dètailed description of rhe solurions proposeil by calileo regarding rhe observation
of Jupiterrs satellites for longirudè decernination at sea is tó be found in the
letter he wrote ro Lorenzo Reaglio on 5 June 1637. (C. calilei, op. cit., X,|1r,
9ò. 0 ).
9. ln CaliÌeo's letter to Lorenzo Reagllo he atso sùgSesrs a mechanisn ro count the
oscillations of the ,,tine-neasuler". Further descriprions are given in ùpeyazioni
Astrononí.lL (c. caLirei, dp. .r:t-,VIII,
45t) ard in thè lctr.r Lo c. ll. Baljaùí
dareo lSpot b r lo, .,. C I ..,
. . .,.\. t., or,.
10. C. Gali1eo, Òp. cit., Xw, 461 .
11. Conceming Caliteo's proposats ro Spain an.t the Netherlands on rhe súbjecr of longirude
see also: E. ?rovèrbio, It ruolo di calireo nella dèterminazione derta lonsirudine,
Cal.enda o t*:L popola,4t),
1984,9a4j-52.
12. I,lernerus, J., in Ptalenae geagraphid.n dnnoLat'iÒ|È, Nórimbergae, j5j4.
ll.
lor the hlstory of rhe precursors and successors of the lunar distance and other
astronomicaÌ nerhods for longirude dererminarion, see: E. C\yot, E1:.staire de la
Cetenninatían de!, 'Longitù.des, La chalr: de Fonds, 1955.
14. Canovai, 5., Vadggi Lli AnerigÒ Vespuccí,.:on La ríta, I'elogio e Lc di|septazíal1e
gíustificatíra
dí questa celeb?e naúi.(1ta!e, rirenzc. 1817.
15.
Gúyot, E., op. cit., 61 .
16.
Patterson, L. D., PeDdúluhs of lhen and Èooke, a)!,,1., jA, 1952, 2j8.
11. On the role played by the asrrononers and lechni.ians of the creenwich 0bservatory in
the developnent of observational in..rqprr".or
longirJde c"r"rm:nauion ir ire
XVIII century, see: ldarncr, D. J., Astrononcrs, artisans and loneirud., in
'llrdnspÒ1.t :I'echnalaglj and SÒcíaL Clnnge", op. cít.,
133-4Ai Warers, D. W.,
op. cít., 143-62.
18. LJaters, D. \,1., op. cít., 160.
l9. Riccioli, G. 8., Alndgestlin,trrúr, Bononiae, 1651.
20. Mersenne, M., Cogítata Ph! sica-Matematícd, phenone,n.! B,1t.LíEtíca, parisii, 1644.
21. On the úse óf rhe nechanical cLock up ro abour rhe middle of the XVII century. see:
Ì1. Proverbio, calileo caÌilei ed i1 probÌema dclla úisu!. del Lenpo, in ,,iL,,orir;
Celerie e Crísi del Sapet,e", Ed. p. calluzzi, rstiruto e ltuseo di Sroria de]le
Sc ienze, firenze, 1984,63-13.
22. Geùra Frisius, De Pdncípiís Ast?anoniae et coÈnagrdphiae, Anruerpiae, j533; see also:
F. lladdison, LIedieùal €cientifi.c ínstlnnents dnd. the d",DeLopment of neDigatíondl.
i.tLstrwnentE in the XVth dnd. xvlth centlar.ieB, coiúbra, 1969, 41-42.
23, Pastor, R., La ciencia.! Ld tecnicd en eL descubrinento d., Ane"ica, Buenos Aires,
1945,
24.
25.
26.
96 .
Chr., Jlr-nre: Conpletet, La Haye, Xv1Ì, 1932, 8,
References to the Mrine clock in rhe Euygens' vorks are given in: H\y1ens, op, cít.,
Huyecns,
Xvrl, 157'236; XVI1i, 7-17, 21-.t2, 114-23, 369-'t3, 449-596, 592-96, 6lt-5-1.
Drùìnond Robertson, J.,Ihe era!,utio of the ciaclara"r,, London, 1931, J43-74.
21.
íbíd. , 144,
28.
Huygeùs,
14a,
lrh.., op. ciL., t',tII, 23A-34,,11tt, 114 11.
rl'e ' ó', -ibu, on o- che iFchrn;c"
(1ocl
103
29. Drlnmond Robertson, J., op. .'í1., xvIII, 150.
30. Huyg€ns, ,p. úii., xvi11, 633-35.
31. ilì'., xvr1, r62 61.
32. Hevelius, Ioll., Mdchina CoeîeÈí'i.s l, cedani, 1673, 369.
33. Drummond Robertson, op. cí!.. t 159.
14. 0r.1 the realizatioD of the first pendulm clocks, seei E, Morpurgo, Ltoralogío e'tL
Penórlo, !.Òna, 1951: E. L. Edwardes "The suspended fobot aDd nev light on early
Pendùlum cÌocks'r, ,4Nt1:quarì tút Haralag!, A, !L1, 1981, 614-26i R Plomb; "Du..h
jnflúen.es in Fren.h clockmaking and vicé-versa in Ehe latter balf of thc
seveùteÈdth t.ntnrytl, Atì.L1.ortti.m Hotologr!, I, Xll, 1974, 28-45.
35. can?ani, e., Dísca?sÒ íntarna d suai nutí atiuol'i 1660, Ed. S. A. Bedini, Mllano, 1983.
16. Campani, M,, Ptoposiziane d'a!íuo1.i q';ustissiní etc., RÒna, 1613.
37. uor!urso, !., "ScetoaDo gli entùsiasmi", La CL.tcridra, 9, I, 1956, 15-18.
38. ratterson, L. D., op. cit., 218.
3s. DrL,mond Robertso!, J., op. .i.1.,158. Huysens Ct\r., Òp. cíx., MlI, 116-17.
40. EùyseDsr Chr. op. ciL., {V!I, 2:14 15, Dr@mond Roberrsof op. .it., 159.
41. Uùygens, Cht., o{). .:it., \uI1I, 12 17, 120-22.
42. 'ibid., 515 19,537-45,636-51.
43, íbid, , 646,
44. Patterson, L. D., op. cít., 2A1 a545. on the discusscd question af tl\e inD.nLí.on of Ehe spiral sprirg see; Drummond
Rob.rtson, op. c;1., 115-87', uorse, D., dnd finch v., John lÌamsteed and the balance
spting,.4Ì!t;q|lttn HÒ?Òi.ot!, 16, IX, 1970, 664-73.
46. Huygcìns, Cht., .p- .:íx.,IvIIt, 501-08, 522-26.
47. 1:.hiC-, XVIr1, 5i3.
48. Drrmond Robertson, op. .'ít,, 162 63.
49. ltuygeùs, Chr., .r. cir., XVIII, 507-08.
50. Patterson, L. D., op. cit., 2a1.
51. HuySens, oD. ciL., X'llI, a?l 35.
52. ib1:d., 508- 12, 532.
53. Drt'mond Roberston, .tp. t:it. j 163.
54. ìlùygens, cl. ttt., Ivlll, 536-38.
55. íb-id. , 546-61 ,
56. íbic.,562-96,
57. Iiaters, D. lt., op. cít., 160,