254 HEATING AS APPLIED IN HORTICULTURE. 



square, hollowed out at the top and bot- 

 tom sides, so as to move on the rounded 

 projections on 

 Fig. 337. the tiles above 



and below it : 

 d is the door 

 of the furnace, 

 also of fire-tile, 

 and suspended 

 from the pul- 

 ley e by means 

 of a round vul- 

 canised India- 

 rubber belt. 

 The arrange- 

 ment will be better seen in fig. 339. This 

 door slides in two grooves in the side 

 bricks, as seen in the elevation. 



Fig. 338 is 

 the eleva- 

 tion, showing 

 both furnace 

 and ash-pit 

 door, slid- 

 ing horizon- 

 tally upon 

 Sylvester's 

 principle. 



Fig. 339 

 the eleva- 

 tion showing 

 the furnace 

 door suspen- 

 ded by a 

 pulley, and 

 opening ver- 

 tically, while 

 the ash-pit 



door opens 



horizontally. 



Williams s improved or Argand furnace. 

 — This furnace is founded upon the prin- 

 ciple of the Argand lamp ; and although 

 sufficiently ingenious and creditable to 

 the inventor, has not been found to act 

 very satisfactorily in practice. In " The 

 Gardeners' Chronicle," an anonymous 

 correspondent, in criticising this furnace, 

 makes the following remarks in regard to 

 its effects : — " In the annexed diagram we 

 have shown how simply and easily the 

 benefits, real or supposed, of the contri- 

 vance in question may be obtained in 

 furnaces resembling those generally used 

 for horticultural purposes. The aperture 

 in the brickwork marked by four arrows, 

 which indicate the course of the entering 



Fig. 339. 



current of air, are the only novelties ; and 

 they are new only in this peculiar ar- 

 rangement ; because, as we have already 

 stated, air has been admitted behind the 

 fire for the same purpose for very many 

 years. In this arrangement, the air 

 which enters by the four channels meet- 

 ing the current of gas at right angles, 

 or rather, indeed, opposed to it, would 

 tend to produce that forced intermixture 



Fig. 340. Whic \ . is 



secured m 



the turpen- 

 tine lamps 

 by the pecu- 

 liarly form- 

 ed chimney, 

 and the de- 

 flecting but- 

 ton placed 

 over the 

 flame." The 

 four arrows show the direction of the air. 

 Fig. 340 will more fully explain its prin- 

 ciple. 



In the " Transactions of the Society of 

 Arts" will be found several kinds of fur- 

 naces described ; and amongst them one 

 in which all the bars of the grate are 

 tubes, for the purpose of admitting a 

 current of air to pass into a long narrow 

 chamber, formed in the bridge behind 

 the fire, which has a communication with 

 the hollow bars, and from them, through 

 a thin aperture, into the flue at the throat. 

 This, with many others that could be 

 named, shows how various are the opinions 

 regarding the admission of air into fur- 

 naces — whether it should be admitted in 

 large or small quantities — whether in a 

 cold or heated state — whether directly 

 upon the fuel through the doorway, or 

 only through the ash-pit bars, &c. It is 

 somewhat surprising that the hot-blast 

 has not been tried upon hothouse fur- 

 naces. The theory appears practicable 

 enough, and it would certainly be worth 

 a trial. 



Amongst the various kinds of furnaces 

 that have been projected, there are none 

 so valuable as those constructed upon the 

 principle of consuming smoke. Of these 

 there are now somewhere above forty, for 

 which patents have been taken out. 



So early as 1 680, a stove was exhibited 

 at the fair of St Germains, near Paris, in 

 which the smoke not only descended, but 



