and the Economy of Fuel. 143 



In constructing the boiler (which is of thin sheet iron), 

 I made an experiment which succeeded even beyond 

 my expectation. The flues under the boiler (and there 

 are none round it) are projections from the bottom of 

 the boiler: they are hollow walls of sheet iron, about 

 9 inches high and an inch and three-quarters thick, into 

 which the liquid in the boiler descends, and which in 

 fact constitute a part of the boiler. By this contrivance 

 the flame is surrounded on all sides, except at the bottom 

 of the flues (where the heat has little or no tendency to 

 pass), by the liquid which is heated, and the fire-place 

 is merely a flat mass of brick-work. The grate is even 

 with the upper surface of this mass of brick-work, and 

 the ash-pit is the only cavity in it. 



In constructing the boiler, provision was made, by 

 omitting or interrupting the hollow walls or divisions 

 of the flues, in the proper places, to leave room for intro- 

 ducing the fuel, for the passage of the flame from one 

 flue to another, and from the last flue into the canal 

 by which the smoke goes off into the chimney, or into 

 the iron tubes by which the hall is occasionally warmed. 



One principal object which I had in view in this 

 experiment was to see if I could not contrive a boile^ 

 which, being suspended under a wagon or other wheel- 

 carriage, might serve for cooking for troops on a march; 

 or which, being merely set down on the ground, a fire 

 might be immediately kindled under it. 



Those who will take the trouble to examine the boiler 

 in question will find that the principle on which it is 

 constructed may easily be applied to the objects here 

 mentioned. But it is not merely for portable boilers 

 that this construction would be found useful : I am 

 convinced that it would be very advantageous for 



