58 
REPORT—-1854. 
substance at its upper end within the needle projecting downwards from it. This 
tube was also surrounded by a bath filled with oil, the surface of which just covered 
the upper end of the tube. A powerful lever acted on a piston carefully packed and 
fitting accurately into the vertical cylinder just mentioned, and the pressure thus 
applied to the oil, filling the cylinder and the tubes, was communicated to the sub¬ 
stance at the upper end of the vertical tube. The substance was then gradually and 
slowly heated by heating the oil in the ball), the temperature of which was known 
by a thermometer with its boll immersed in it. The temperature was thus increased 
till the needle dropped down from the top of the tube. To ascertain the exact instant 
when this took place, a small compass was so placed near the top of the tube con¬ 
taining the magnetized needle, that the needle of the compass was deflected about 
90° from its nntural position, its return to which was the signal that the magnetiad 
needle had fallen, and the substance melted. The temperature of the bath at that 
instant gave the temperature of liquefaction. 
The following ore some of tire results obtained 
Substances experimented 
upon. 
Pressure in lb*, to the 
square inch. 
Temperature Fahr. at which it 
liquedcd. 
Spermaceti. 
0 
7790 
11,880 
o 
124 
O 
140 
0 
176-5 
Wax . 
0 
7790 
11,880 
148-5 
166-5 
176-5 
Sulphur. 
0 
7790 
11,880 
255 
275-5 
285 
Stearine. 
0 
7790 
11,880 
138 
155 
165 
course wnen the weight 0 was on the piston, the substance was unner 
spheric pressure, or about 15 lbs. to the square inch; the pressure of 779° 
per square inch was that at which the Britannia Bridge had been raised. J' r j 
Hopkins had also tried the metallic alloys which fuse at law temperatures, but 
not detected any elevation of fusing temperature required by increasing the pressun-, 
relied upo cx P er ‘ raeut3 required to be repeated and confirmed before they coul 
O t *^ ?ormv l ai for the Maximum Pressure and Latent Heat of Vapour*- HjJ 
VV ilham John Macquokn Ranking, C.E., F.K.SS. Land, tf 
■ y 
„ 1 . Th r5 Utho r > , roa80n ' Q g from the supposition that the pressure exerted by » K'P 
- lts va P our - when in contact with each other, is the result o 
pansive elasticity in the vapour, balanced by an attractive force which tends 
rnni ens - e ,h ,° surfac c of the liquid or solid, many years since arrived* 
temnPMif" that , t , le law connecting the maximum pressure of a va P° u f Jlbv 
the follo\v[ng V f OU l ^ P ro ^ a ^ty be found to be represented to a near approxi 
log P=A-5_g_&c. ; 
F 
MiTthpr T denotes the temperature racusured from the absolute zero of the I 1 ,, 
P the maximum pressure; and A, B, C, *c.. constants to 
The tn . ,0ra / !X P Cn ’ uen tal data for each substance. . ffl0r netef 
■ m lhe raost P r ohabie position of the absolute zero of the perfect gas therm 
274° for the Centigrade scale, 
Havimr ... 4 dl 0, 2 for Fahrenheit's scale. nrr «ur« 
steam usinJthr til ! 0rmulu ,n M - Rcgnaulfs experiments on theP^^ 
expedmentfl dam hT with three constants A. B, C, determined fru® ! 
SBTSSiS A T\ th ° rcsult3 of experiment and calculation 
with MSte* he Wl - 0lc Cxtcnt of the experiments. The same was ^ ^ 
ZrL oily * e *l>erimcuts on the vapour of mercury, using a form 8 * 8 
