26 General Notices. 



Art. II. General Notices. 



Witty'' s Improved Furnace. — When we noticed this furnace, in a for- 

 mer Number, we were not aware of the extent of the improvement which 

 it is calculated to effect; the inventor having, in a private letter which 

 accompanied his communication, chiefly insisted on its power of burning 

 waste coal. We have since seen some printed remarks, accompanied by 

 testimonials, which show that the most important advantage of Witty's fur- 

 nace is the burning of the smoke, by which a saving of from 20 to 30 per 

 cent of fuel is obtained,- and the atmosphere in the neighbourhood of the 

 fqrnace is not polluted with smoke. It also appears that rather less attend- 

 ance is required than with a common furnace, whether for hot-houses, 

 steam-engines, or dwelling-houses. 



The first principle of excellence in the construction of this improved 

 furnace is the way in which it is supplied with fuel. By the common mode, 

 the moment the door of the furnace is opened, a rush of cold air sweeps 

 through the flues, or under the boiler, carrying off much heat. Cold, and 

 perhaps moist, coal is then thrown on the very centre of the fire, which not 

 only reduces the heat, but occasions a quantity of dense smoke to be emit- 

 ted from the chimney; and this smoke, when once formed, cannot be 

 burned except at a temperature (3000° Fahrenheit) that will melt iron. 

 This temperature would, of course, require an amazing expense of fuel. 

 The mixture of about one twelfth of atmospheric air with carburetted 

 hydrogen, of which smoke of coal is chiefly composed, produces com- 

 bustion at a high temperature. By throwing on a fire unprepared coal, not 

 only this inflammable gas (carburetted hydrogen) is generated, but also 

 nitrogen, carbonic acid gas, and other non-inflammable gases ; and it has been 

 proved, that when smoke contains one sixth part of nitrogen, or one sixth 

 of carbonic acid gas, it will not inflame. Hence the difficulty of consuming 

 smoke. In order to overcome this difficulty, Mr. Witty divides the con- 

 sumption of coal into two distinct processes : viz. carbonisation, by which the 

 coals are thoroughly dried, and freed from their watery and gaseous matter; 

 and combustion, in which the carbonised coal, or coke, is consumed along 

 with the watery and gaseous matter which is distilled from that portion of 

 coal which is undergoing carbonisation. By these two processes, the maxi- 

 mum of heat is obtained from any given quantity of fuel ; and this without 

 one particle of smoke. By Mr. Witty's plan, the atmospheric air is no- 

 where admitted but through the coke fire, and this inflames all the gaseous 

 matter, as it is evolved from the coal undergoing distillation. 



It is important here to observe, that, as a very high temperature is 

 essentially necessary for the consumption of smoke, that object can never 

 be effected under a boiler in which water is not raised much beyond 

 the boiling point. Now, the great superiority of Mr. Witty's plan is, 

 that the smoke is consumed before the flame and the heat come in 

 contact with the boiler. We are the more anxious to direct attention 

 to this, because, in heating by hot water, it will be found necessary to place 

 the boiler not immediately over the fuel, but rather over the commence- 

 ment of the flue ; or, at whatever may be the point where all the gaseous 

 matters are consumed. It will be seen in our advertising sheet that this 

 furnace has been erected in several gardens, and that it has given the 

 highest satisfaction. Mr. Miller of the Bristol Nursery has had two fur- 

 naces put up to his steam boilers, which, he says, effectually consume the 

 smoke, and produce a greater quantity of heat with less fuel. Mr. R. Mil- 

 ler, the very intelligent gardener at Alton Towers, who has had the ma- 

 nagement of several of the hot-houses and conservatories there, strongly 

 recommends it as being preferable to any other furnace that he has seen, 

 producing a great heat generally diffused, with less coal and no smoke. 

 There is one of Witty's furnaces erected at Lee's Nursery, Hammer- 



