W. J. M. Rankine, Esq., on the Elasticity of Vapours. 35 



In order to calculate the constants, the following experi- 

 mental data have been taken, assuming that, on Dr Ure's 

 thermometers, 180° were equal to 100 centigrade degrees. 



The values of the constants in equation (1.), calculated 

 from these data, are as follows, for inches of mercury and 

 Fahrenheit's scale : — 



Alcohol, specific gravity, 0-813. 

 Ether, boiling point, 105° F. 

 Ether, boiling point, 104° F. 



Log/3. 



Los 



6-16620 

 5-33590 

 5-44580 



3-3165220 

 3-2084573 

 3-2571312 



5-7602709 

 5-5119893 

 5-3962460 



Absolute zero 462°'3 below ordinary zero. 



The curves represented by the formulse for those three fluids 

 are laid down on the diagram which accompanies this memoir 

 (Plate I.), and which, in the engraving, has been reduced to 

 one-fourth of the original scale. The horizontal divisions re- 

 present the scale of Fahrenheit's thermometer, numbered from 

 the ordinary zero ; — the vertical divisions, pressures of va- 

 pour, according to the scales specified on the respective- 

 curves. The points corresponding to the experimental data 

 are surrounded by small circles. 



