540 Account of Experiments 



steam from one of the loaves in question (after it has 

 been heated to the temperature of 212) the ioj loths, 

 equal to \\ of a pound of water, which each loaf is 

 known to lose in being baked. 



Now it appears, from the result of Mr. Watt's in- 

 genious experiments on the quantity of latent heat in 

 steam, that the quantity of heat necessary to change 

 any given quantity of water already boiling hot to steam 

 is about five times and a half greater than would be suffi- 

 cient to heat the same quantity of water from the tem- 

 perature of freezing to that of boiling water. 



But we have just observed that 20 Ibs. of ice-cold 

 water may be heated to the boiling point, with the heat 

 generated in the combustion of i Ib. of pine-wood. It 

 appears, therefore, that 20 Ibs. of boiling water would 

 require 5! times as much, or 5* Ibs. of wood to reduce 

 it to steam. 



And if 20 Ibs. of boiling water require 52 Ibs. of 

 wood, \\ of a pound of water boiling hot will require 

 loToiu" of a pound of wood to reduce it to steam. 



Of pine-wood. 

 Ib. 



If now to this quantity of fuel T$$<Hhr 



we add that necessary for heating the loaf 

 to the temperature of boiling water, as 

 above determined TooifoT 



This gives the total quantity of fuel neces- 

 sary for baking one of these loaves of 

 bread iW/oV 



Now, as these loaves, when baked into bread, weighed 

 2 Ibs. 5-i loths = 2 \\ Ibs. each, and required in being 

 baked the consumption of iW^A of a pound of wood, 

 this gives for the expense of fuel in baking bread 



