102 Of the Management of Fire 



boilers, I was for some time quite at a loss to account 

 for this difference. In all my experiments with boilers 

 of different sizes, from the smallest saucepan up to the 

 largest kitchen boilers, I had invariably found that the 

 larger the quantity of water was which was heated, 

 the less, in proportion, was the quantity of fuel neces- 

 sary to be employed in that process ; and so entirely 

 had that prejudice taken possession of my mind, that 

 when the strongest -reasons for doubt presented them- 

 selves, they were overlooked ; and it was not till I had 

 searched in vain on every side to discover some other 

 cause to which I could attribute the unexpected appear- 

 ance that embarrassed me, that I was induced I may 

 say, forced to abandon my former opinion, and to be 

 convinced that what I had too hastily considered as a 

 general law does not in fact obtain but within narrow 

 limits; that although in heating certain quantities of 

 liquids there is an advantage, in point of the economy 

 of fuel, in performing the process on a larger scale, in 

 preference to a smaller one, yet when the liquid to be 

 heated amounts to a certain quantity this advantage 

 ceases; and, if it exceeds that quantity, it is attended 

 with an expense of fuel proportionally greater than 

 when the quantity is less. 



What the size of a boiler must be, in order that the 

 saving of fuel may be a maximum, I do not pretend to 

 have determined. I think, however, that there are some 

 reasons for suspecting that it would not be larger than 

 some of the kitchen boilers used in my experiments. 

 But I recollect to have promised my reader that I 

 would not give him my opinion without laying before 

 him at the same time the grounds of those opinions. 

 In the present case they are as follows : 



