31—1850.] 
plieated 12 It consists essentially of three 
ts. Ist. A 
reury; 2d. A 
p 
tand in * tube w 
void of air at ‘the Big of 3 30 e but the height of 
most con ntinually. 
* as it 
without any visible 
air has weight ; pe — dry it has been found | 
he 
that 100 cubic in igh a little more than 
31 i 1 
ressing on the 
mercury in he tube, for, as previously stated, the 1570 
siding of the mercury, when the tube was inverted 1 
namel Ys 
THE ee ae a 
CHRONICLE. 485 
inch, its pressure n the, 
— 
p 
885 
* 
us 
tracted from the observed height; for if the scale were 
moveable, as some are, and its t adiusted 
0 f the 2 in the cistern, 
—.— of mercury. e mark, 29 inches, would be 2, of r than 
he fluid usually Legg g wel barometers, con- the top 4 the column. ee 
with a universal pressure equal to 
an inch hi 
3 it is n 
euu 
reury, because it is the heaviest of ar known sub- |t 
stances retaining fluidity at ordin eratures, and | quo 
therefore most convenient, on account ‘of its requiring e, the neutral point; 
a shorter length of tube to contain a certain weight; observed height when this is 
i a po mas paar 
tion will not materially affect the general mean of 
observations, m more especially if — n point is 
"E at or h the — 
ands in pm locality where the et aing intended 
t quent extrication would r 
the 
on the mercury in the cistern 
must 
n whi reury in its 
a little lower, in — of what 
action. 
pe: S shall suppose it 
The wo lak be of an 
lindri at the side, nent 
* 
m S. 12 0Z. 1 fi the 
weight of 30 cubic inches of mercury at the tempera- 
ture is weight will be found sufficient to 
squeeze down the mercury in the cistern and force it up 
ure 
for although the latter bears 
he s cre ge 
re. N 
Cistern Tube. 
A= Atmospheric mer cing ( 8 pres- 
B Pressure ‘of loaded Ge ‘of, 80 inches of of 
mercury s, 
ince to the square 
L 3 
the 
perin 
1s | extremity was then herme 3 7 fo 
as 
tube me at the top, the balance will be thus 
pr 
EXPERIMENT 2, 
ä —7* 3 
ares ibe, 
8 grs. 
ts in — 2. 
oe asin experiment 7 — e hal have 
but column 
3 inches — 
column; total, 60 in 
of 30 ins. 
Ss N 
— 
reury. 
(2) B+ 830 T3060 en of mere 
er fi dude may, however, be em- to be placed, say 30 inches for places near the level of 
, | ployed on the same principle, pe * tube is made the tion for 
long ee to contain as much o will balance 
t of the atmos e 8 ly, a water 
eee in the Ts | 
1 
rfac y the sai 
If the internal 
employed, ee. not so rea dily frozen i water At an inch, the eistern, in order to 
0° water is 13.568 times, or a ‘little —— have a diameter o 
ter than mercury. ere | space sec eh * ay tube, probably — 0.025 inch 
mn of 30 inches of mercury is sufficient more, acco: e thickness of the glass. The 
n ern 
to balance the atmosphere, a ter cistern might * of much s ons without 
than 33 feet 11 inches in height would be increasing the amo ction, provided the 
required to do the same . If a space of 3 inches diameter of the tube were diminished in proportion. 
comprise th trem the fluctuations | Their capacities would still be as 1 to 100 if the cistern 
of a mercurial barometer, the corresponding range were little than 2 inches in diameter, and the tube 
in a er barometer wo 402 inches. The | 4 of an inch; but then, in consequence of narrowing 
tube of the water barometer at Some ouse the tube, the correction for capillary action — be 
wa essrs. Pellatt and Co., at the ine 
Ca apillary action has the greatest effect in narrow 
tubes; but it is necessary to observe that its action is 
t the upper end, the extremity being drawn out into a | quite the reverse as reg wa f 
fine tube ready for sealing with the blowpipe ; and a | tube is placed in a basin of mercury, the surface of the 
small stop-cock was fitted to it. The cis of rtion in the tube is found to be lowe that in the 
arometer was a s. copper steam-boiler, 18 inches | basin ; but if a similar tube is placed in a basin o 
long, 11 wide, and 10 deep. It was nearly filled with pi ae the reverse occurs ; the water in the tube rises 
disti water. Heat being applied, and s e- | above che level of that outside the tube. The effect, 
the water was fore e tube, ed a at top, to um 
the height at which it Sali have stood in the Torri- oe s, therefore, ie be a In wide tubes the amount 
if such co ave y nas Aeri of depressi: t ‘ttle n a tube of an inch 
formed by filling the tube with water, and then i in diem meter, it is only 0.007 — but in one of a tenth 
ing it in the 3 i more steam pressure of an inch, it is 0.142 i It is, howe wever, considerably 
would of course be s 
ficient to force the water to the | less in boiled tubes. 
al tip of the par 2 5 height of 40 feet. The tapering The correction for tem the most 
closed. r . hot weather it may amount to the t 
more. According to the experiments = 
. and Petit, mereury prestige yd r, alk wich i 
Tarenheite thermometer, ygyo 0) ei tt 
| occupied at 32° rometers ‘shoald 
| furnished with a L dipping in 1 8 23 
75 * N the — agp the 
e to 
temperature; 3 
4 
en case, and * — n a 
odged ina w 
wat eee a | 
3 coat convolution of a windin 
red 
may be rendered 
* 
zero of the centigrade an aumur’s scales, is 
—— universally a dopted po tape to which the mer- 
is reduce a bar ae stand at 30 inches, 
easil is 60°, and if at 
rena employed a lead Sge, bent at the lower —4 
n the principle of the syp arometer, so that when | e 
the air was light, and the column in the vacuum conse- 
| quently lowered, the water rose in the open -e end, 
tupwards ; and the e ary when the air was heavy. 
and fall. Cl ft id 
Tube. fl 
No atmospheric pressure, 
W. 
= 29 Ibs. 8 oz. 248 gr. | ey 
ations by ex nsion — contraction in the cane A siaii rende 
of the pipe, and alterations in the specific gravity o P. 
a with the pocite gariz Bot: the would acquire 66° 
i i swage saa 18 om 
i identi i water were | the mean time, n 
ghen 1 2 ie f t no gee 42 a be about meeeg of a 
2 inches, | inch ; this barometer will stand at 
30. 100, em its fellow eee at 30. To-day 
re exerts a e p 3 to-morro 
recisely the same; but if 3 
expansion be day, the barometer will rise 
erease 
of oe of 20°, or from 1097 80 6025 : and d this | and thus lead e supposition that the air has be- 
circumstan I of e xpansion come heavier ; andit is only when the correction for ten 
counteract the 
In order that the p ressure of the 8 may be U that the ee continues the same. W 
in the — of water nearly +4, 0 sa = 
Iso nec mercury is above 32°, the ——— 
reury. 
{3) A $ B=60 ; and by g B, this ROA 
giv ives 
4) A—60—B ; by No.1 ee 30, t therefore 
5) A 30 inches of mi mercury, and also equal to 
B; so that we may employ —— > or B, as in the 
preceding experiments, with the effect. 
e atmosp e cistern, 
— pressing with — sagen a 
— to to fs 5 if below 32°, the correction 
must be ad: 
The best table pes correction for temperature is con- 
ne calculated by N Schuma 
in a “ Rep to the yal 
ir 
to + 2 to the indications ‘of — m 
ese corrections should be made for capacity, | 
e action, and N ture. correction 
for px. tage: A Pig: nds the relative Range of 
58 tube cistern; e pane difference | cher. 
3 the l the 2 correction ; 
pons — it rad * it should always be marked 
the instrumen w marked by the th 
best makers, and — is likewise the 3 2 8vo. 
i i i mercury stood w e scale 
. . mensuration from the 0 — 8 = 
: pense 
3 
1 
and instructions for m 
fess the haag 
n be m 
ed ssi sd te — The 3 cistern were made as 
dig p ee. 5 inches in diameter, and the capacity of the 
be — nae ae aae aio: for altho € 1 
capacities | crease the amount of capillary action, yet as this action 
Es 
peat 
