xvi Historical Sketch of the Physical Sciences, 1818. 
210° of the degree at which the elasticity of steam is required: 
Let 7 = the mean ratio between 210° and the temperature at 
which the elasticity of the steam is required. Then 28-9 + n. 
log. r = log. of the elasticity required. Above 210° we add 
below 210°, we subtract n log. r. 
The following table exhibits the elasticity of the other vapours 
examined by Dr. Ure. 
Ether. Alcohol, Sp. Gr. 0°813. Naphtha. Oil ofTurpentine 
Temp. Elast. |Temp. | Elast. |Temp.| Elast. Temp. | Elast. |Temp.| Elast. 
34° | 6:20 32° | 0-40 |173°0°| 30°00 | 316° | 30-00 |304-0°) 30-00 
44 8:10 40 0°56 |178°3 | 33°50 | 320 31:70 |307°6 | 32°60 
54 | 10°30 45 0-70 |180°0 | 34°73 | 325 34:00 |310°0 | 33°50 
64 | 13:00 50 0°86 |182°3' | 36:40 | 330 36°40 |315°0 | 35°20 
7A | 16°10 55 1:00 |185°3 | 39°90 | 335 38:96 |320°0 | 37:06 
84 | 20-00 60 1:23 |190°0 | 43-20 | 340 41°60 |322:0 | 37°80 
94 | 24-70 65 1°49 | 193-3 | 46°60 | 345 44:10 |326°0 | 40°20 
104 | 30-00 70 1-76 | 1963 | 50°10 | 350 46°86 |330°0 | 42:10 
2d Ether. | 75 2:10 |200°0 | 53:00 | 355 50°20 |336:0 | 45:00 
105 | 30:00 80 2°45 |206°0 | 60°10 | 360 53°30 |340:0 | 47°30 
110 | 32-54 85 2°93 | 210-0 | 65:00 | 365 56:90 |343:0 | 49-40 
115 | 35:90 90 3°40 | 214-0 | 69-30 | 370 60°70 |347-0 | 51°70 
120 | 39°47 95 3°90 |216°0 | 72-20 | 372 61-90 |350:0 | 53°80 
125 | 43-24 | 100 4°50 |220:0 | 78°50 | 375 64:00 |354°0 | 56°60 
130 | 47:14 | 105 5:20 |225°0 | 87-50 3570 | 58-10 
135 | 51-90 | 110 6°00 |230:0 | 94:10 ' 360:0 | 60°80 
140 | 56:90 | 115 710 |232°0 | 97°10 362°0 | 62-40 
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3. Specific Heat of Solids at different Temperatures.—That 
every substance has a specific heat peculiar to itself, or that 
every substance requires a quantity of heat peculiar to itself, in 
order to produce a given change of temperature, was first 
pointed out by Dr. Black. Experiments to determine the spe- 
cific heat of bodies were afterwards made by Dr. Crawford and 
Mr. Wilke, by Lavoisier and Laplace, and more lately by Mr. 
Dalton. But it was not agreed upon, whether the specific heat 
of the same body remains permanent at different temperatures, 
or whether it does not vary according to some particular law. 
Dr. Crawford made a set of experiments to’ prove that it remains 
unaltered at all temperatures as long as a body does not change 
its state; and Dr. Irvine’s theory of heat depended in a great 
