256 



HEATING AS APPLIED IN HORTICULTURE. 



its leading feature. No furnace, however 

 constructed, can consume its own smoke 

 upon first kindling the fire, nor until the 

 fire has attained the temperature neces- 

 sary for the consumption of smoke, which 

 appears to be never less than 1000° of 

 Fahr. scale. 



To understand the principle of this 

 furnace we may observe, that there is 

 a carbonising plate, on which the coal is 

 submitted to two processes — namely, car- 

 bonisation and combustion. Over this 

 plate is formed an arch of fire-brick, or 

 large Stourbridge lumps, either of which 

 radiates sufficient heat to produce a 

 powerful effect upon the coal, which 

 instantly gives out plentiful streams of 

 carburetted hydrogen gas. The gas, 

 being thus formed at a high temperature, 

 is immediately inflamed by a due pro- 

 portion of atmospheric air rushing 

 through the heated coke at the bottom of 

 the furnace, which, meeting the gas, pro- 

 duces a brilliant and lasting fire, and, 

 from its purity of flame, prevents soot 

 from lodging in the flues, if common 

 attention be given to the first lighting ; 

 and it can be kept'in for months together 

 without relighting if required. 



In this furnace a third, or thereby, 

 only of the floor consists of a grate, and 

 that placed close to the throat. The 

 inclined plane on which the coal is placed 

 is set at an angle of about 35° or 40°, and 

 occupies the whole space from the grate 

 to the feeding-door. This door is smaller 

 and differently formed from those in 

 common use. It has merely sufficient 

 opening to admit of the supply of the 

 fresh coal, and is very completely closed 

 with a flanged lid to exclude air. The 

 fuel is pushed forward upon the inclined 

 plane by means of a square piston, 

 wrought by a handle from without ; and 

 by reversing the motion, the piston is 

 brought back to its original place, to ad- 

 mit of fresh supplies of coal. The first 

 arrangements being completed, the fire 

 being kindled, and the door completely 

 closed, the plane and the arch are thus 

 converted into a retort. The heat of the 

 fire and the hot air rising through it, 

 which is strongly reverberated from the 

 arch, promotes the distillation of the 

 nearer portions of the coal. The gases 

 as they rise are whirled into the current 

 towards the flue, and, meeting with the 



rush of heated air through the fire, are 

 inflamed and completely consumed. This 

 process continues till the coal is perfectly 

 coked which is then pushed forward by 

 the screw, to make place for fresh supplies 

 of coal. If properly attended to, these fur- 

 naces work well ; but it is difficult to get 

 men to attend to them, as the feeding of 

 furnaces has hitherto been carried on with- 

 out system or regard to correct principles. 



A scientific remedy is noticed in " The 

 Pharmaceutical Times " for the consump- 

 tion of smoke, which consists in intro- 

 ducing a cast-iron tube from a boiler to 

 convey a column of steam above, and to 

 be dispersed by a rose nozzle over the 

 surface of the coking coal. "Decomposi- 

 tions and new combinations thus take 

 place, which effect the entire combustion 

 of the inflammable gases, and the imme- 

 diate disappearance of a column of black 

 smoke, which, till the turning on of the 

 steam, had hovered in the shaft of the 

 chimney." Where steam is employed, 

 this is easily effected, and at little waste 

 of power. A more simple and almost as 

 efficacious a method may be applied in 

 any hothouse furnace, even of the most 

 common construction, by leading a 

 metallic tube, finely perforated at the 

 end, to terminate over the fire, the other 

 end being connected with a cistern of 

 water. The jet of water, about as fine as 

 a small needle, being thrown upon the 

 fire whilst burning briskly, will gene- 

 rate sufficient steam in the furnace to 

 secure the combustion of all smoke. 

 The accidental leaking of a boiler over a 

 fire-place kept constantly at work led to 

 the discovery of this simple remedy. 



The majority of smoke-consuming fur- 

 naces, although in form and minor de- 

 tails differing from each other, nearly all 

 rest on one general principle — namely, 

 the admission of an adequate supply of 

 air behind the fire-bridge, and just at the 

 point where the supply afforded by the 

 ordinary draught ceases to be effective. 

 The carbonaceous vapour, being still 

 heated to a high degree, becomes in- 

 stantly ignited on being brought in con- 

 tact with the air, so that a sheet of flame 

 may be seen to sweep along the bottom 

 of the boiler, and ■ no smoke is produced. 

 If the extra supply be cut off, the flame 

 immediately ceases, and its place is occu- 

 pied with a dense volume of black smoke, 



