1819.] Philosophical Transactions for 1818, Part II. 215 
ment, represented by the length of the column of mercury in 
inches which that vapour is capable of supporting. 
eid A eee 
Temp. |Elasticity,| Temp. | Elasticity. Temp. |Elasticity.| Temp. Elasticity. 
_|———_ | 
24° 0-170 165-00 10°80 250-09 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°16 255°0 67°25 295°0 129-00 
55 0-416 185°0 16°90 257:5 69°80 297°1 133-90 
60 0-516 190-0 19-00 250°0 "12°30 298°8 13740 
65 0-630 195:0 21:10 260-4 72°80 300-0 139-70 
10 0°726 200:0 23°60 262°8 75°90 300°6 140°90 
15 0°860 205-0 25°90 2649 17°90 302°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 81-90 305°0 150°56 
90 1-360 |, 216-6 33°40 269°0 84-90 306°8 15440 
95 1640 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 2-100 225°0 39°11 273°7 91-20 311-4 164-89 
110 2°456 226°3 40:10 2750 93-48 312°0 167-00 
115 2‘820 230:0 43:10 QT5°T 94-60 | Another exper. 
120 3°300 230°5 43°50 2179 97-80 312:0 165°3 
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 5170 240-0 51-70 283°8 107°70 
145 6600 242-0 53°60 2852 112°20 
150 7-530 2450 56°34 287°2 114°80 
155 8°500 2458 57°10 289°0 118°20 
160 9-600 248-5 60°40 290°0 120°15 
Dr. Ure has discovered that if 30 = elastic force of steam at 
212° be divided by 1:23, the quotient will exhibit the elastic 
force of steam at 10° below 212°. This last quotient divided by 
1:24 will give the elastic force of steam at 10 below 202° ; this 
last quotient divided by 1-25 will give the elasticity of steam at 
10° below 192°, and so on. To obtain the force of steam above 
212°, we have only to multiply 30 by 1-23 for the force at 222°;. 
that product multiplied by 1:22 gives the force at 232°; this last 
product multiplied by 1-21 gives the elasticity at 242°, and so on. 
Or this empirical formula of Dr. Ure may be represented more 
generally in this way: 
28-9 represent the elasticity of the vapour of water at 210°. 
Let x represent the number of decades above or below 210° of 
the degree at which the elasticity of steam is required. Letr 
= the mean ratio between 210° and the temperature at which 
the elasticity of steam is required.* Then log. 28°9 +n. log.r 
= logarithm of the elasticity required. Above 212° we add, and 
below 212° we subtract 2 . log. 7, 
Dr. Ure ascertained, by a set of experiments conducted in the 
same manner, the elasticity of the vapours of alcohol, sulphuric 
* By mean ratio is meant the terms 1:23, 1°24, 1-25, &c. or 1°23, 1-22, 1:21, &c. 
as far as is required, added together, and the sum divided by the number of 
terms, 
