10
discussed at grea.t length many other forms of steam
WHAT A UNIT OF HEAT C A N D O .
carriages , amO)lg which was a plan for a s tro et omni·
GEN ERAL BURNSIDE'S LETTER.
bus, which would carry t hirteen persons besides the
I n tal k i n g and writing about heat., physicists have
use wele felt the need of some mode of ex p ressi n g a de fi n i te
novel , the principal one being that horses were un­ quantity, aud the idea was suggested of calling that
able to understand or rather comprehend t.he nature quantity which is sufficient to raise the temperature
of a wagon that movcd without an y apparent mean s of one pound of water one degree of Fahrenheit' s
of propulsion . 'fh e exhaust steam was also a source scale a unit .
Havin g thus exactly defined a given
of . � oyance to h orses which it was desirable t o qu a ntity o f heat, it i s su rpris i n g to find h o w many
firema1!- r and steerer .
The obj ectiona to i ts
This it W <l S tho ugh t could be overcome b y
working t he steam
truths in relation t o the action of caloric may be
General Burnside has written a l etter to President
Lincoln in reference t o the late dis a ste r at Frederick s­
burg , in which h e most characteristically and mag­
n animonsly assumes the whole rpsponsibility of the
occurrence .
" The pen· is mightier than the sword , "
and i n this respect the G eneral has shown himsel f
the
greatest soldier of t h e war.
We cannot recall , at
this w r i ting, any other case of a like nature, in which
at -a-higb. pressure, a n d cutting i t briefly and clearly expressed, which before, it was
t
off short, thus diminishing i s volume. T h e c o s t o f difficult to c o mprehend and convey. I t i s an impres ­
bared his own forehead , and laid h imself open to
horse power, was also considered in balancing the
terms in scientific discnssions.
speaking o f the honorca dead who fell upon that day ,
amount in favor of steam .
fe w words by the medium of units.
working street carriages by steam , as compared with
merits o f the two systems, and resulted by a small
The Euglish roads and
streets are so much better than ours, generally, that
inventors in that country have not the same dis­
advantages to con t end with as w e h ave .
the
Whether
steam w a go n will ever supersede , to any extent,
sive illustration of the valne of accurately defined
Specific heat,
the command i ng officer so
whatever criticism might be visited upon him.
fighting superh u m a nly, the General conveys to those
will raise the temperature of a po un d o f water one
being a man , grieves with them and shares their sor­
A u n i t of heat
degre e , but it will raise the temperature of a pound
who mourn, the assurance , at least, that h e
row.
Our losse8, says the sam e authori ty, have been
man who predicted the u n i versal system of railroads
heat o r its specific heat is one thirty - third, o r three
after the enemy r efused to
of tin is
ecuted with o u t loss.
that now twine almost every country on the globe
as with
a net.
Who shal l say, then , that when the
difficulties and prej udices which now exist are over­
come, w hat new schemes and inventions may not be
inaugurated ?
SINKING OF IRON CYLINDERS FOR PIERS.
The employment of c a st iron cylinders for fo unda­
tions in water, such as bridge and dock piers, has
been tried in America to a limited extent, but wi th
also,
of a pound of tin 20° . Or, it as usual, greatly overated .
They amount to 1 , 152
ta k es o ne thirty - third o f a uni t of heat to rai se the killed , with about 7 , 000 wounded ; we also took
of mercury 3 3 0 , and
temperature of a pound of mercury o n e degree.
Years ago, h e would have been a rash
In
for instance, may be explained in a very
t h e employment o f catt.le i s a ques tion that remains
to be solved .
nobly and generonsly
We
accordingly say, t hat the capacity of mercury for
one hundredth s , expressed decimally
0·05.
A clear i!l�a �f
latent heat,
0 .03, and
that
als o , m a y be v e r y briefly
700 pris o ners, which last h ave been paroled .
The re­
treat- which seems to have been carried out only
l ea ve their intrenchments
and attack us-was a masterly affair, and w a s ex·
The P r esid e n t , in acknowledg­
ing this l e t ter, has issued an address to the army
raise the tempera­ under General Burnside, in which h e congratUlates
Fah . to 2120 the them upon their valor and endurance , and assures
water must absorb 152 units of h e at ; then i t will them that altho u gh they were unsuccessful , the at­
conveyed by lll e ans of u!,lits.
To
ture of a pound o f water from 600
absorb 1 , 000 units more wi thout nising its tempera­
tempt was not an error, nor was it any thing but a
As this heat which changes the water from the liquid
our brave men ; surely a cause that has such he ar t y
ture at all, but these 1 , 000 units con vert it into s team .
state to that of vapor does not show itself either to
Well may Mr . Lincoln thus eulogize
pure accident.
supporters w a s not b o r n to d i e .
In c o m m o n with
future use the touch or when tried b y the thermometer, i t is most of the Nor t he r n people we were overwhelmed, at
first, when the news and exten t of o ur disaster reached
They consti tute an called hidden or latent heat.
such satisfaction that in all likelihood their
u p o n an exten sive scale . .
�
improved devel pment of foundations laid by the
w il l be
A unit of heat applied tc
mechanical wort will raise
772 pounds of m at ter one foot ; in other words, it
diving· bell system. In 1779 the celebrated Smeaton
will perform 7 7 2 foot - pound s of work.
first used the diving-bell for repairing the founda _
As it takes more heat to raise the te m perature of
tions of Hexham Bridge , in Englan d , instead of maf ­
water one degree a t some temperatures than it doe3
p
ing coffer- dam s .
The next good im rovement was
D . Potts' s pnenmatic process of sinking iron cylin­
ders,
( old
which was illu s trat e d on page 1, Vol .
VIII,
series ) of the SCIENTIFIC AMERICAN. The principle
of this method may be briefly stated as fol lows : - An
at othcrs, i t was necessary to fix some temperature at
which the measure
h,<s been
iron cylinder to be sunk as one of the piles of the
soil ; it is then connected by a flexible hose to a re­
ceiver, which is furnished with a trap valve in the
bottom , opening downwards, and put in com muni·
cation with a three-barreled air - pump.
'fh e pump is
put in motion, and the air i s exhausted from within
the cylinder and receiver, the silt or sand is forced
up in the reservoir by the external pressure of the
atmosphere, and , as soon a s the reservoir i s filled, a
valve at. the bottom is opened and the contents al­
lowed to flow o n t , after which the valve is closed and
the operation repeated until the pile is
required
depth .
Th e cyl i n d e r sinks
sunk t.o the
by
its
own
weight and the external pressure of the atmosphere.
The method i s not available when applied t.o stony
grou n d , as water would flow in under t.he edges of
the cyl i nd e r and vitiate the external vacuum.
Fah .
agreed upon ; water !It that temperature
i r on cylinders o f the new bridge at Harlem, near this
city.
This meth od consists in filling the cylinder
with com pressed air by which means the water i s e x­
pelled from below the tube, and men excavate and
work i nside.
In both
used on the top of each cylinder during the opera..
Another method consists in
forming each cylinder with a screw on its lower ex­
tremity, and giving it a rotar y motion hy which it is
forced into the groun d .
In many situations this
plan has been very successful.
Another plan consists
in forming each screw cylinder with a disc at its
lower cnd, leaving a hole in th e center through which
a wrought-iron pipe is carried down through the
pile ,
projecting some
inches
below
its
botto m .
Water i s forced d o w n this p i p e u n d e r pressure, a n d a
r otary motion is given to the cylinder at the
time .
left untried to secure those righ ts and privileges for
which
we are
fighting and which w e properly deem.
inestimable ; without these life itself is valueless.
. . . .
THE CHANGES OF A PIECE OF SILVER.
Much has been said and written about " the wooden
wal l s of old England, " meaning thereby the w ar- ships
If we p l a ce a piece of pure silver in nitric acid and
of that nation ; but, from late experiments, w e j udge
a
they are not quite so good s paper . The special
pears ; the solution l ooking exactly like pure water .
experiments with guns and iron- clad targets-the
add a p r o per quantity of water, the silver is dissolved
�
as completely as sugar i s i n water, nd wholly disap­
If now we evap o r ate a portion of the water and set
the solu tion away , w e sh all find in the course of a
few hours t.hat the bottom of the vessel is covered
Government committee that was appointed to make
latter representing the side of a ship-deserve credit
for developing m a ny new facts connec ting with the
power of resistance possessed by various material s ,
with beautiful , white, flat plates, which are crystals a n d t h e penetratin g powers of others .
of nitrate of silver, the metallic silver in combination
with nitric acid.
The nitrate of silver has some very
sin gular properties.
If kept free from cont a c t with
other substances, it may be exposed t o the light for
any length of time without any change from its pure
white color .
O r it may be applied to cotton or the
s k in or hair in the dark without any change in color .
same
This method has been found very successful in
sillking such cylinde!s in v e ry hard river bottoms.
THE number of applications for pensions
penetrate plates which break cast-iron sho t like glass .
A target was con s t r ucted entirely of iron, under the
impression that it would prove superior to one com ­
posed of wood and iron combined ; but it was found
inferior, owing to the greater amount of vibration
induced by the sho t striking. Hard wood, especially
But if it is applied moist to any vegetable or animal teak, was supposed, until latel y , to b e the best back­
ing material which could be employed for the iron
It is the coloring agent in indelible
plates ; but, strange t o ' relate, it has been found by
If we place crystals of nitrate of silver i n water ,
were lately con structed with one-inch plate· iron­
a few minutes.
ink.
they arc quickly dissolved, and if we throw a little
table sal t-the chl oride of so d ium-into the solntion ,
the chlorine in the salt, forming the chloride o f sil­
experiment t o b e inferior t o pape r .
teak- wood , the otllQr backed by the same thickness
6-pounder, using elon gated shot
and
Metals may be silvered cold by means of the chloride
it was ill the paper one.
turns black when ex po s ed to the action of the light .
o f silver.
If we mix chl oride of silver with carbonate of soda,
Two targets
the one backed by fourteen inches i n thickness of
ver. This is a white lustreless p owde r , and gradually
2�
5�
a Whitworth
inches in length ,
in diameter, and t h e penetration w p, s found
to be t wice as great in the timber-backed target that
at with
The targets were then fired
a l 2 - po u nder, and with like results .
The re ·
sistance of p aste - boa rd to shot has attracted so much
and heat the mixture in a crucibl e to a very bright
attention o n the other side of the Atlantic that fur ­
decompos e d .
and tOl1gher material
red, it is d issolved, and both of the substances are
combines with
The chlorine leaves the silver and
the sodium of
the
soda, forming
chloride of sodi u m-tabl e salt-the carbonic acid es­
capes as
a
gas, and the
silver i s
l eft in the metalic
state in the hottom of the crucible.
Th us w e have silver first as a white solid me tal ,
then a liquid
like w ater, then in crystals like salt,
then as indelible ink, then as a gray or black pow­
th e r experim ents are t o be m a d e w i t h i t .
A denser
than wood can be made of
straw and cornstalk p aper .
Who knows. but the seas
may yet be navigated in paper ships ?
POMPEIAN windo w-g l a s s , of which panes have been
discovere d as large as 20 by 28 inches , h as proved , on
examinat i o n , to
have : been c a s t in a manner similar
m ak i n g plat e'glass, except
to tha t now followed in
m ade at der , and fi nally again a s a metal . And th e se are that it was not rolled flat, 8 S now, by metal cylin·
only a very s m al l p art of th e forms which i t may be de r s , b u t p r es se d out with a wooden mallet, so that
its t hicknes s is not uniform.
made to assume.
the Pension Bureau at Washington , up to December
12th, t hi s year, was 7 , 9 1 1 .
Thus it has
been found that steel and wrought-iron shot will
nes with of paste-board . They were fired at with
of these methods, the cylinders the silver leaves the ni tric acid, and combi
used are plain casti rrg s ; an air-tight trap hood being
tions of excavating .
what the North will d o .
And
, PAPER FOR SHIP.BUILDING.
A plan the reverse o f this, called Hughes' s pneu­ substance and exposed to the light, it turns black in
matic syste m , has been employed for sinking the cast.­
j. e. t o
this is j ust
No lawful means will be
" pick the fl i n t a n d t r y her again . "
being easily obtained.
foundation is covered with an a i r- ti ght cap, placed in
p osition , and allowed to sink t h rough the water and
should be tak e n , and 60°
us, but we feel like adopting the backwoodman ' s ad­
vice t o his comrade when his rifle m i ssed fire,
© 1863 SCIENTIFIC AMERICAN, INC.