H4 Of the Management of Fire 



estimate ; but, as they make part of a work which I 

 understand is preparing for the press, I dare not antici- 

 pate what Mr. Kirwan will himself soon lay before the 

 public. 



According to this estimate it appears that 1089 Ibs. 

 of oak produce as much heat in their combustion as 

 600 Ibs. of pit-coal. Now, if we suppose that the pine- 

 wood used in my experiments is capable of producing 

 as much heat per pound as oak, and I have reason to 

 think it does not afford less, from the quantity of 

 pine-wood used in any of my experiments, it is easy to 

 ascertain how much coal would have been necessary 

 to generate the same quantity of heat ; for the weight 

 of the coal which would be required is to the weight of 

 the wood actually consumed, as 600 to 1089. 



In one of my experiments (No. 31), 11,368 Ibs. of 

 water, at the temperature of 65!, were made to boil 

 with 650 Ibs. of pine-wood. As when the experiment 

 was made the mercury in the barometer stood at about 

 28 English inches, the temperature of the water when 

 it boiled was only 209^-, consequently its temperature 

 was raised (209! 65!) 144 degrees. Had the water 

 been boiled in London, or in any other place nearly on 

 a level with the surface of the sea, it must have been 

 heated to 212 to have been made to boil, consequently 

 its temperature must have been raised 1463 ; and to 

 have done this, instead of 650 Ibs. of wood, 66 ij Ibs. 

 would have been required (140 is to 650 Ibs. as 146^ 

 to 66 4 Ibs.). 



If pit-coal were used instead of wood, 363^ Ibs. of 

 that kind of fuel would have been sufficient ; for the 

 quantities in weight of different kinds of fuel required 

 to perform the same process being inversely as the 





