HEATING BY HOT-AIR STOVES. 



217 



matter of course, when the weather is 

 cold, it should be supplied with more fuel 

 than if the cold were less intense ; and to 

 make the fire burn freely, or arrest its 



combustion, the regulating aperture e, by 

 which it is supplied with cold air, must 

 be opened and shut for those purposes. 

 By a little attention to this instrument 



Fig. 290. 



Fig. 291. 



Fig. 292. 



on the part of the individual who attends 

 the stove, both fuel and labour can be great- 

 ly economised. For example, when left 

 quite open, (which it ought to be when the 

 stove is first lighted,) the fuel would be 

 consumed in two or three hours' time ; 

 whereas, if nearly closed, it will burn 

 without a fresh supply for twelve or fif- 

 teen hours. An index being placed round 

 the circle, the time it will last is readily 

 ascertained. 



The purity of the air produced by the 

 patent air-stove proceeds from the con- 

 struction of the fire-box. It is formed of 

 a circular tube of burned fire-clay, a ma- 

 terial which is a slow conductor of heat, 

 consequently not liable to overheat the 

 air like fire-boxes made of metal. It is 

 also more durable than iron, if exposed to 

 a constant great heat. To give the tube 

 strength at a moderate thickness, and 

 perfect safety against the escape of car- 

 bonic-acid gas mixing with the heated 

 air, it is girt round with a casing of iron, 

 which is brought into close contact with 

 the whole of its external surface, on a 

 principle entirely new. To this casing of 

 iron the zigzag flues are attached ; and 

 their being of this formation gives to the 

 VOL. i. 



stove an extensive heating surface ; and 

 the heated air, having to zigzag in its 

 ascent, is discharged uniformly, not being 

 subject to accelerations by concussions 

 from the wind. 



When a humid atmosphere is required, 

 a dish containing water is placed on the 

 sand which encloses the fire-box. 



These stoves have the cold air gene- 

 rally supplied to them in the apartments 

 where they are situated ; but in some 

 cases it is brought from the external 

 atmosphere, and introduced below them, 

 as represented by fig. 292 at / /. 



Lawes hot-air furnace. — This is another 

 example of heating by hot air, accom- 

 panied with a considerable circulation. 

 It was first communicated to " The Gar- 

 deners' Chronicle," from which our dia- 

 gram is taken, by Mrs Tysson of Foulden, 

 in Norfolk, in whose establishment it is 

 said to have given satisfaction. Contrary 

 to what might be expected, the air heated 

 by this furnace loses less of its humidity 

 than we were prepared to expect : this is 

 stated to be owing to the rapidity with 

 which the cold air is made to pass through 

 the pipes, so that it is said to be totally 

 unaltered except in temperature. Mrs 



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