and the Economy of Fuel. 107 



fuel consumed, it must depend in a great measure on 

 the size of the fire-place ; and when it is required to 

 heat a large quantity of water, or of any liquid, in a very 

 short time, either the fire-place must be large, or (what 

 in my opinion would be still better) a number of separate 

 fire-places two or three, for instance must be made 

 under the same boiler. The boiler should be made 

 wide and shallow, in order to admit of a great number 

 of flues, in which the flame and smoke of the different 

 fires should be made to circulate separately under its 

 bottom. 



The combustion of the fuel, and consequently the 

 generation and communication of the heat, may in the 

 same fire-place be considerably accelerated by increasing 

 the draught (as it is called) of the fire ; which may be 

 done by increasing the height of the chimney, or by en- 

 larging the- canal leading to the chimney, and keeping 

 the damper open, when that passage is too small, or by 

 shortening the length of the flues. 



The master brewer having expressed a wish that some 

 contrivance might be used by which the water might be 

 made to boil a little sooner in the new boiler, I made an 

 alteration in its fire-place which completely answered 

 that purpose. 



But, besides the desire I had to oblige the master 

 brewer (who only thought how he could contrive to 

 finish as early as possible his day's work), I had another 

 and much more important object in view. Having had 

 reason to suspect that flues which go round on the out- 

 side of large boilers do little more than prevent the 

 escape of the heat by their sides, which, with infi- 

 nitely less trouble and less expense, may be prevented by 

 other means, I was desirous of finding out, by a deci- 



