116 REPORT 1844. 



end view. In these representations it will be seen that the gases emitted 

 from the furnaces a, a x are conducted along the internal tubes into the re- 

 turn flue b. From b they cross under the boiler below the ash-pit into the 

 flue c, and from thence along the opposite side of the boiler into the main 

 flue d, which communicates with the chimney. From this description it will 

 be observed that the gases do not unite until they have reached ee at the 

 end of the boiler. At this point a change immediately takes place in the 

 gaseous products, and that from one of two causes, as follows. Suppose the 

 furnace a x to be newly fired, and the fuel in it in a perfectly incandes- 

 cent state ; it then follows that the gases passing from a will not only be 

 different in their constituents to those from a x, but they are at a much 

 higher temperature; and both furnaces having received air as a constant 

 quantity through the fixed apertures j^, it will be seen that in the event of 

 a surcharge of air on one side, and a diminished supply on the other, that 

 their extremes are neutralized by the excess of oxygen thus introduced and 

 the increased temperature which effects ignition at the point e, where combi- 

 nation takes place. All that is therefore necessary is to replenish the fires 

 alternately every 20 minutes in order to effect the combustion of the gases 

 without the least appearance of smoke. These and the increased recipient 

 surface are the leading properties of this boiler, which, compared with others 

 having single flues, is found to be greatly superior either as regards the com- 

 bustion or ceconomy of fuel. 



General Summary of Results. 



Inbrieflyrecapitulatingthe experiments, observations and results obtained, 

 it will be seen that in the procurement and employment of heat, a number of 

 important matters have to be considered. 



First, the quality and properties of the fuel used. 



Secondly, its treatment in the furnace, and the supply of air requisite for 

 its combustion. 



Thirdly, the form of boilers, and the extent of their absorbent surfaces. 



Fourthly, the concentration and ceconomy of heat. And 



Lastly, the prevention of smoke. 



These have been treated upon in their respective order, and all that now 

 remains is to collect them into form, and draw such conclusions as will 

 enable practical men to understand and apply the means necessary for their 

 fulfilment. 



From what has been stated, and from the many facts collected and expe- 

 riments made, it will appear conclusive that a much better and more com- 

 prehensive system of combustion can be accomplished ; and by attention to 

 the following results, great and important advantages may be obtained. 



Amongst the varied species of fuel enumerated in the foregoing experi- 

 ments, there will be found ten different sorts of coal, each exhibiting its 

 peculiar properties and compounds. For the sake of brevity and deduction, 

 these may be divided into three kinds, namely the anthracite, the bituminous 

 and splint qualities. Of the anthracite we have little experience beyond a 

 knowledge of its properties and the absence of smoke. It is a coal which 

 requires a large supply of oxygen for its combustion, and instead of the 

 furnace usually employed for the consumption of the bituminous kind, it 

 would require one possessing the power of a reverberatory or a strong blast 

 acting upon it, and that under circumstances of a minute division of its parts. 



The bituminous kind is however what we have most to do with, and on . 

 reference to its constituents, it will be seen that a specific quantity of atmo- 

 spheric air is absolutely necessary for its combustion, amounting, as already 



