1821.] Causes of Calorific Capacity, Latent Heat, &>c. 436- 



•519599 log. 9-7156683 A 



A x 8 = 7-7253464 



A x -2 = 9-9431337 



• 30 log. .. 1-4771213 



•140 log. 9-1456014 



The tension of aqueous vapour, therefore, at 32° Fahr. is *140 

 in. by Dr. Ure, by Mr. Dalton it is -20, and by Mr. Southern 16. 



Example 2. — Let the temperature be 165° Fahr. then by 

 Table 3, T = 1130 1. 



1130-1 log. 3-0531169 



•002783313 log. 7-4445621 

 3-14541 0-4976790 



2-26371 



0-88170 log. 9-9453208.... A 



A x 8 = 9-5625664 



A x '2 = 9-9890642 



30 log. 1-4771213 



10-684 log. 1-0287519 



Hence the tension should be 10-684 in. By Mr. Dalton it is 

 10-68, and by Dr. Ure 10-80. 



These are as unfavourable cases for the theory as any I think 

 which can be picked out in temperatures beneath the boiling of 

 water ; let us, therefore, see what will be the result in some of 

 the superior temperatures. 



Example 3. — Suppose the tension be required at 250° Fahr. as 

 I am not aware that Dr. Ure has made any allowance for the 

 difference between the indications of an air and a mercurial 

 thermometer, I have in computing the values of the constants 

 reduced his temperatures, supposing them mercurial, to air indi- 

 cations. This will make a difference in the values of the con- 

 stants, which, if Dr. Ure* has accounted for, it will be needful to 

 rectify. Making this re-allowance would not, however, affect 

 the theoretical accuracy of the formula, which would only require 



* I perceive the Doctor has not accounted for it : he appears to consider the mercu- 

 rial as the true indications of temperature. 



2 f2 



