MECHANICS AND USEFUL ARTS. 37 



exalted to the same condition, and any excess of carbon forms, with free 

 hydrogen, marsh gas, or light carburetted hydrogen. The vapor of water is 

 thus made to give up not only its constituent elements to form new com- 

 pounds with oxygen, producing in the change great heat, but a great part 

 of the heat absorbed by the water in becoming steam is also liberated in this 

 change of its physical and chemical condition. Moreover, as all these 

 products of combustion and of chemical reaction pass together over the 

 bridge-wall of the furnace into a space from which atmospheric air is not 

 excluded, it then and there happens that any free hydrogen, light carbu- 

 retted hydrogen, or oxide of carbon which have previously escaped com- 

 bustion, take fire and burn, yielding up their quota of heat to the general 

 aggregate. 



Such is the intensity of heat in that portion of the furnace where these 

 reactions take place, that only the most solid structures of refractory fire- 

 bricks will endure it, and the color seen throughout that portion of the 

 furnace is o'f the purest white. 



In view of the facts already stated, it is easy to understand why it is that 

 when the reactions described are once set up, the admission of a free current 

 of atmospheric air should immediately check the energy of the combustion, 

 and soon result in total suspension of the peculiar energy of this furnace. 

 The air containing only one-fifth of its bulk of oxygen gas, the active agent 

 in combustion, the access of so large a proportion of cold air, four-fifths of 

 which are not only indifferent, but positively prejudicial, from the quantity 

 of heat it absorbs, it happens that the temperature of the mixing-chamber 

 is rapidly reduced below the point at which carbon can decompose vapor of 

 water, and the instant that point is reached the arrival of fresh supplies of 

 steam completes the decline of energy, and the furnace commences forth- 

 with to belch forth from its stack dense volumes of smoke and watery 

 vapor. When in proper action, not a particle of smoke is visible from the 

 stack of a furnace in which wet fuel is burning, and, what is more remark- 

 able, the reactions are so evenly balanced that no wreaths of watery vapor 

 are observed; while, in the earlier stages of combustion, before the proper 

 temperature in the mixing-chamber is reached, both these products are seen 

 in great abundance. 



The language of the inventor, in describing the construction of his furnace 

 for burning begasse, is as follows : 



" I build two furnaces, side by side, each nearly square in its horizontal 

 section. Towards the top I draw in the wall in such a manner as to form a 

 kind of dome, with a sufficient opening at the top to feed the begasse. In 

 each furnace-chamber there should be a partition of fire-brick, extending 

 across it from front to back, and rising nearly to the top, dividing it into 

 two nearly equal parts. The main chamber of each furnace should be 

 divided into two parts, upper and lower, by a fire-brick grating about one- 

 fifth the height of the furnace above the hearth, the back end of the grate 

 being a little lower than the front. 



"In each furnace, at the front, on each side of the central partition, and 

 immediately under the front end of the grate, should be doors for feeding 

 wood and other dry fuel, and directly under these doors, at the hearth of the 

 lower chamber, should be draught openings, capable of adjustment, to sup- 

 port combustion in the lower chamber. Extending across the back of both 

 furnaces, and opening into both by flues, is a mixing-chamber, into which 

 all the gases from both furnaces enter in a highly heated state, and mix and 



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