Chemistry. xv 
observe the height of the column of mercuty. A fourth person 
sat at a table, and wrote down the temperature and the corres- 
ponding heights of the mercury. ‘These experiments, like many 
others of mine which I had projected, and partly completed, 
were interrupted in consequence of bad health, and I have never 
found leisure or inclination to resume them. If they have been 
of no other use, they enable me at least to appreciate with tole- 
rable accuracy the degree of precision to which experiments 
made in this way may be carried. The following table exhibits 
the elasticity of steam at different temperatures, according to the 
results given by Dr. Ure. 
Temp. |Elasticity.| Temp. (Elasticity, Temp. |Elasticity. Temp. |Elasticity. 
249 0-170 165°0° 10-80 259°0° 61-90 292°3° | 123-10 
32 0-200 170°0 12°05 251°6 63°50 294-0 126-70 
40 0-250 175:0 13°55 254:5 66°70 295°6 130-40 
50 0'360 180-0 15°16 2550. 67°25 295°0 129-00 
55 0°:416 1850 16:90 257°5 69°80 297-1 133-90 
60 0-516 190-0 19-00 260°0 72°30 298°8 137-40 
65 0°630 195-0 21:10 260°4 72°80 300°0 139°70 
70 0°726 200:0 23°60 262°8 75°90 300°6 140-90 
75 0860 | 205°0 25°90 2649 77°90 802°0 144-30 
80 1-010 210°0 28°88 || 265:0 78:04 303°8 147-70 
85 1:170 212:0 30:00 267°0 81:90 3050 150-56 
90 1-360 216°6 33°40 269-0 84-90 306-8 154-40 
_95 1-640 220°0 35°54 270°0 .| 86°30 308°0 157-70 
100 1-860 221°6 36'70 271'2 88-00 310:0 161-30 
105 27100 225°0 39°11 2TS*T 91-20 311-4 164-80 
110 2-456 2263 40:10 | 275°0 93-48 312-0 167:00 
115 2°820 230:'0 43:10 QT5'7 94°60 |Another exper. 
120 3°300 230°5 43°50 | 277-9 97°80 312:0 165°5 
125 3°830 234°5 46°80 | 279°5 101'60 
130 4-366 235°0 47°22 | 280°0 101°90 
135 5:070 238-5 50°30 | 281°8 104-40 
140 5°770 240°0 51'70 | 283°8 107°70 
145 6-600 242-0 53°60 | 285:2 112°20 
150 1 530 245-0 56°34 | 287°2 114:80 
155 8-500 245°8 57:10 | 289-0 118:20 
160 9°600 248°5 60°40 | 290°0 | 120715 
Absolute precision would require a small correction in the 
above table for the dilatation of the glass tube. It is obvious 
that the capacity of the glass tube gradually increases with the 
temperature; so.that the elasticities given in the table are a little 
below the truth ; and the error increases with the temperature. 
The absolute expansion of glass, given in a preceding part of this 
paper, from the experiments of Dulong and Petit, will enable any 
person who is so inclined to apply this correction. 
_ Dr. Ure’s empirical formula for representing the elasticity of 
steam at different temperatures, which hes been explained in 
the Annals of Philosophy, vol. xiii. p. 215, is very simple and 
imgenious, and must be of considerable use to engineers in calcu- 
lating the force of steam at different temperatures. It is as 
follows: Let m represent the number of decades above or below 
7 
