the Barometric Formulce, (^'c. 



661 



the Constants of Barometric Formulae, which accompanies ihis Appendix, I have represented 

 the expression ^Vff' hy the character S, and the expression aF„ by the character 



S'. So that for practical purposes, S = 8'. — Q. E. D. 



I now bring forward Bessel's equation for calculating the elastic forces of vapour of 

 water (expressed in metres), corresponding to temperatures of Centigrade thermometer, 

 accompanied by some constant logarithms, useful in facilitating calculation. 



Let J^i be the elastic force (or tension) of vapour of water, corresponding to temperature 



T + T' . . 



— -r— (being the arithmetic mean of temperatures, as given by the detached thermometers). 



Metres. , ^ /t + t' V 



7=^,= 0-0051229 X 10+1O2W2-1 0-00006S6826(-^j 



Log 0-0051229 = 3-7095159. 

 Log 0279712 = 2-4467111. 

 Log 0-0000625826 = 5-7964536. 



Bessel's Equation for calculating Elastic Forces [or Tension) of Vapour of Water, adapted to 

 English inches and Fahrenheit thermometer. 



Let F be the elastic force, corresponding to temperature t, Fahrenheit. 



Eng. In. 



/^= 0-0613265 X 10 



+ 0-01C7757 . (' - 0-0000193156 . fi. 



Log 0-0613265 = 2-7876482. 

 Log 00167757 = 2-2246806. 

 Log 00000193156 = 52859082. 



Table of Elastic Forces (or Tensions) of Vapour of Water, corresponding to the Temperatures 

 (Fahrenheit) 0°, 32°, 50°, and 100°, as calculated hythe ahove Equation o/Bessel, and as obtained 

 from Anderson's Tables, made from experiments by Dalton and UaE. 



