HEATING BY HOT-AIR STOVES. 



219 



&c, p. 1187. Fig. 296 is a transverse 

 vertical section of it. " The products of 

 combustion of the fire, k, rise up between 

 two brick walls, so as to play upon the 

 bed of tiles /, where, after communicating 

 a moderate heat to the series of slanting 

 pipes, whose areas are represented by the 

 small circles a a, they turn to the right 

 and left, and circulate round the succes- 

 sive rows of pipes b b, c c, d d, e e, and 

 finally escape at the bottom by the flues 

 g g, pursuing a somewhat similar path to 

 that of the burned air among a bench 

 of gas retorts. It is known that two- 

 thirds of the fuel have been saved in the 

 gas-works by this distribution of the 

 furnace. For the purpose of heating 



Fig. 296. 



hothouses, the great object is to supply 

 a vast body of genial air ; and there- 

 fore, merely such a moderate fire should 

 be kept up in h as will suffice to warm 

 all the pipes pretty equally to the tem- 

 perature of 220° Fahrenheit ; and, indeed, 

 as they are laid with a slight slope, are 

 open to the air at their under ends, and 

 terminate at the upper in a common 

 main pipe or tunnel, they can hardly be 

 rendered very hot by any intemperance of 

 firing. If the tubes are made of earthen- 

 ware, the construction of this stove will 

 cost very little; and they may be made 

 of any size, and multiplied so as to 

 carry off the whole effective heat of the 

 fuel, leaving merely so much of it in the 

 burned air as to waft it fairly up the 

 chimney." 



A very powerful stove is described by 

 Dr Ure in " The Dictionary of Arts and 

 Manufactures," p. 1187. Fig. 297 "ex- 

 hibits a vertical section of a stove, which 

 has been recommended for power and 

 economy ; but," says the learned Doctor, 

 " it is highly objectionable, as being apt 



to scorch the air. The flame of the fire a 

 circulates round the horizontal pipes of 

 cast-iron, b c de, 

 lg " which receive the 



external air at 

 the orifice, and 

 conduct it up 

 | through the se- 

 ries, till it issues 

 highly heated at 

 k I, and may 

 thence be con- 

 ducted wherever 

 it is wanted. The 

 smoke escapes 

 through the 

 chimney /. This 

 stove," he ob- 

 serves, "has evidently two obvious 

 faults : first, It heats the air-pipes very 

 unequally, and the undermost far too 

 much ; secondly, The air, by the time it 

 has ascended through the zigzag range 

 to the pipe e, will be nearly of the same 

 temperature with it, and will therefore 

 abstract none of its heat." Such are the 

 faults of most of the air-stoves now in 

 use. 



Polmaise hot-air stove. — This mode of 

 heating has pretty generally been set 

 down as the invention of the late Mr 

 Murray of Polmaise, near Stirling. That 

 gentleman, it appears, only revived, and 

 probably unknown to him, a mode of 

 heating invented by Dr Desaguliers, and 

 described by Bradley so early as 1719. 

 It appears to have lain nearly dormant 

 from that period, till Mr Sylvester em- 

 ployed it some years ago to heat the 

 Derby Infirmary, as well as several hot- 

 houses in the same county. Mr Mur- 

 ray's revival of Desaguliers' method in 

 1841, created at the time a considerable 

 degree of interest, more especially as the 

 editors of the two leading horticultural 

 newspapers of the day took opposite po- 

 sitions in the matter, and each brought 

 forward an array of evidence, conjecture, 

 and opinion, to bear for or against the 

 utility of this system. 



We shall briefly detail the objections 

 that present themselves to it. But first 

 let us describe the stove in its most per- 

 fect form ; and we conceive we cannot do 

 this better than in Mr Meek's own words, 

 accompanied with his diagrams as pub- 

 lished in " The Journal of the Horticul- 



♦ 



