MECHANICS AND USEFUL ARTS. 31 



feet deep, and two or three feet in diameter, closed at the bottom, 

 and having a hopper at the top, through which fuel is supplied. This 

 chamber, at a certain height from the bottom, is in direct connection 

 with the body of the furnace, so that flame may issue as freely from 

 it as from the fire-place of an ordinary reverberatory furnace. In the 

 sides of the generator, at a certain distance from the top, is a series 

 of three or four small, round holes on .the same level, and at some 

 distance lower down is another similar series of round holes. These 

 holes are for the passage of the air intended to support combustion in 

 the interior of the generator, which is blown in either by a fan or 

 some other convenient blowing-machine. Now, when the generator 

 is full of incandescent fuel, and air is injected through the lateral 

 holes, carbonic oxide gas is copiously produced and passes into the 

 furnace, as there is no other place of egress, the hopper at the top 

 being supposed to be shut. As it escapes from the generator, it is 

 met with a current of heated air, or, as it is technically termed, " hot 

 blast," which is injected downwards from the roof of the furnace at 

 or near its junction with the generator, either in several jets or in one 

 continuous sheet. The carbonic oxide while still hot is thus burnt, 

 and the heat developed is sufficiently intense even to melt wrought 

 iron by the hundred weight. The air which supplies the generator 

 is also previously heated ; and in the Swedish furnaces the apparatus 

 for heating the blast consists of a series of cast-iron pipes fixed at the 

 lower part of the stack. Hence only the waste heat of the furnace 

 is employed for this purpose. It is usual to place a hollow cylinder of 

 iron round the generator, so as to leave a closed space between its in- 

 ternal surface and the exterior of the generator ; and into this space 

 the hot blast is introduced, whence it passes through the two rows of 

 holes previously described into the interior of the generator. The 

 atmosphere of such a furnace can be rendered either reducing or oxi- 

 dizing at will by regulating the amount of blast. At the bottom of 

 the generator is a door, by means of which the ashes or clinker from 

 the fuel may be withdrawn. These furnaces can be so modified as to 

 suit any kind of fuel. A recent writer in the London Times advo- 

 cates their use even for the burning of anthracite. He says, " This 

 kind of coal gives intense local heat, but this inconvenience might 

 easily be remedied by introducing along with the air into the gener- 

 a<~or a certain proportion of steam. This steam would be decomposed, 

 with the formation of carbonic oxide and hydrogen gases and some 

 carbonic acid, and a considerable reduction of temperature would be 

 the result. But the heat thus removed from the chamber would be 

 subsequently restored in the body of the furnace by the burning of 

 the combustible gases derived from the decomposition of the steam, 

 so that there would be no loss of heat, but only a transference of it 

 from the generator, where it is not wanted, to the furnace, where it is 

 applied. The fact is, our mineral fuel has been so abundant, and so 

 easily accessible, that it has been most cruelly wasted. But matters 

 are not quite so smooth as they used to be, and necessity is beginning 

 to compel attention from our iron-masters to the subject of econo- 

 mizing fuel in every possible way. The old reverberatory furnace is 

 only a clumsy sort of gas furnace ; but in the Swedish peat-furnaces 



