1 82 On the Construction of Kite hoi 



pable of being performed with a very small expense of 

 fuel. 



The quantity of heat, or rather the quantity of fuel, 

 by which any given culinary process may be performed, 

 may be determined with much certainty and precision 

 from the results of experiments which have already been 

 made. 



Suppose, for instance, it were required to compute the 

 quantity of dry pine-wood (what, in England, is called 

 deal) used as fuel, and burned in a closed fire-place, 

 constructed on the most approved principles, to boil 

 100 Ibs. of beef. And, first, we will suppose this beef 

 to be in such large pieces that 3 hours of boiling, after 

 it has been made boiling-hot, are necessary to make it 

 sufficiently tender to be fit for the table ; and we will 

 suppose, farther, that 3 Ibs. of water are necessary to 

 each pound of beef, and that both the water and the 

 beef are at the temperature of 55 of Fahrenheit's 

 thermometer (the mean temperature of the atmosphere 

 in England) at the beginning of the experiment. 



The first thing to be ascertained is how much fuel 

 would be required to heat the water and the beef boiling- 

 hot; and then to see how much more would be required 

 to keep them boiling-hot three hours. 



And, first, for heating the water. It has been shown 

 by one of my experiments (No. 20, see page 81) that 

 2OtV Ibs. of water may be heated 180 degrees of Fah- 

 renheit's thermometer with the heat generated in the 

 combustion of i Ib. of dry pine-wood. 



But it is required to heat the water in question only 

 157 degrees; for its temperature being that of 55, and 

 the boiling-point 212, it is 212 5 5 =157; and if 

 i Ib. of the fuel be sufficient for heating 20^ Ibs. of 



