68 Of the Management of Fire 



inches, consequently water boils at Munich at a lower 

 temperature than at London. The difference is even 

 too considerable to be neglected: it amounts to 2^r 

 degrees of Fahrenheit's scale, being 209^ degrees at 

 a medium at Munich, and 212 degrees in all places 

 situated near the level of the sea. To render the 

 results of my experiments and computations more sim- 

 ple and more generally useful, I shall always make due 

 allowance for this difference. 



Having, from the actual result of each experiment, 

 made a computation on the principles here described, 

 showing what (for the want of a better expression) I 

 have called the precise result of the experiment, it is 

 evident that these computations show very accurately 

 the comparative merit of the mechanical arrangements, 

 and the management of the fire in conducting the ex- 

 periments, in as far as relates to the economy of fuel ; 

 for the more ice-cold water that can be made to boil 

 with the heat generated in the combustion of any given 

 quantity (i Ib. for instance) of fuel, the more perfect 

 of course (other things being equal) must be the con- 

 struction of the fire-place. 



Under the head of PRECISE RESULT I have some- 

 times added another computation, showing how much 

 " boiling-hot water " might, according to the result of 

 the given experiment, be kept boiling " one hour " with 

 the heat generated in the combustion of " i Ib. of the 

 fuel." Though I have called this a precise result, it 

 is evident that in most cases it cannot be considered as 

 being very exact, owing to the difficulty of estimating 

 the quantity of fuel in the fire-place, which is uncon- 

 sumed at the moment when the water begins to boil. 



In the foregoing example, in making this computa- 



