452 Mr. Herapath on True Temperature, and the [Dec. 



Dr. Ure, that the ebullition actually took place at 212° Fahr. the 

 barometer being 30 inches. 



In one experiment Rumford distilled 29*61 French grammes 

 of vapour into 2781 grammes of water at 55° Fahr. and found 

 the mixture 67-5° Fahr. These data give W = 2781, w = 29'61, 

 T = 1023*7, and t = 1172-6. To shorten the calculation, we 



W 2781 



may put — = g9<61 



1023-7 x 93-921 + 1172*6 x 



= 93*921, and then we shall have t =» 

 = 1035*6, which corresponds with 



93-921 + 1 

 66*8° Fahr. *7° below the observation. 



In another experiment he distilled 24*40 grammes of vapour 

 on the same quantity, 2781 grammes of water, at 57-}- Fahr. and 

 found the temperature raised to 67*5° Fahrenheit. Hence 



W = ^1 = 113*9754, T = 1026, and t = 1172*6. Therefore, 



is 24-40 ' 



1026 x 113-9754 + 2149-76 1AO r «-o T l fu * * co 



t= ..on--. ; = 1035*8, or o/° Fahr. that is *5° 



113-97a4 + 1 ' 



beneath the experiment. The following table contains these 

 calculations collated with the experiments : 



Authorities. 



Thomson 



Ure 



Rumford, 

 Ditto. . . 



Quantities mixed, with their temp, 

 in Fahr. 



Vapour. 

 Weight. Temp. 



1*0 



200*0 

 29*61 

 24*40 



212° 

 212 

 212 

 212 



Water. 

 Weight.] Temp. 



9 62*0° 



32340 42*5 



2781 55*0 



2781 57*25 



Temperature of the 

 mixture by 



Exper. 



178*6° 

 49*0 

 67*5 

 67*5 



Theorv. 



178*8° 



49*3 

 66*8 

 67*0 



Excess of 

 theory above 

 experiment. 



+ 

 + 



•2° 

 •3 

 •7 

 •5 



M. diff. --•175 



Philosophers will perceive from this and the other specimens 

 I have given, that we are not more unfortunate in our investiga- 

 tions of the mathematical laws of " Latent Heat " than we have 

 been in any of the rest of our inquiries. 



Cor. 2. — Substituting the numbers thus found for b and b' ', we 



shall have t' 



6 w t + 11 



6 to t + 



6 



l w' t' 



all the vapour being condensed, and 



T = 



. (to + to') 



all the water being vaporised 



1 1 . (to + n>') 



By the former of these theorems, if we take w — 100, w' = 1, 

 t = (201*2° Fahr.) 1163, and t f - 1172*6, we getr' = 1172*7, 

 or 212° Fahr. ; that is, 1 oz. of steam at 212° Fahr. condensed in 

 100 oz. water at about 201° Fahr. will raise the temperature of 

 the water to 212° Fahr. the same as I have stated p. 102 of the 

 present volume of the Annals. 



