56 ANNUAL OF SCIENTIFIC DISCOVERY. 



bustion, by which more than one half the heating effect is lost, and gases 

 dangerous to health are accumulated and escape into the apartment. 



Second. The heat evolved in the air chamber and its connections, should 

 with the least possible loss be transmitted to the air of the apartment or 

 building which it is the design of the furnace to warm. To attain this end 



o o 



through the medium of the air chamber, it is necessary to have regard to the 

 extent and form, and radiating as well as conducting character of the surface 

 of the stove, to the mode of entrance and distribution of the inflowing air, 

 and to the prevention, as far as possible, of the escape of heat through the 

 walls of the air chamber itself. 



2d. To secure the healthful operation of such a furnace, three principal 

 conditions arc to be observed. 



First. The gases produced by combustion of the fuel must not be suffered 

 to mingle, even in minute proportions, with the air which is to be inhaled- 

 Of these the most noxious are the carbonic oxide and sulphurous acid gases. 

 The former, when the action of the furnace is perfect, undergoes a further 

 combustion, converting it into carbonic acid a less noxious product; but 

 the latter, or sulphurous gas, is entirely incombustible. It is evolved in 

 considerable quantity from even the purest varieties of anthracite, is espe- 

 cially prone to escape, and is eminently deleterious when breathed habitually, 

 even in small amount. To guard against such a result, the stove must 

 be constructed with as few junctures as possible ; and these must be so 

 formed and so connected as to remain air tight, in spite of the warping, and 

 the alternate expansion and contraction of the materials due to changing 

 temperature. 



Second. The air of the air chamber must be warmed evenlv and ade- 



v 



quately, without bringing it into contact with surfaces so highly heated as to 

 cause the organic matters contained in it to be burned or otherwise chemi- 

 cally altered. In order to fulfil this condition, the arrangement must be such 

 as to present to the included passing air a large warming surface heated to 

 a moderate temperature. 



Third. The air, in being supplied with an increase of heat in the air 

 chamber, must also be supplied with a corresponding increase of moisture. 

 This is requisite to maintain its natural degree of humidity, or that appro- 

 priate to the temperature, without which it is felt to be unpleasantly dry, 

 and when habitually breathed, proves highly detrimental, and even ruinous, 

 to the health. 



Such are the leading requisites of a perfect hot air furnace ; and to unite 

 them all in one and the same construction, is the difficult, and, as yet, unat- 

 tained result, to which the ingenuity and science of our inventive mechanics 

 ought to be earnestly directed. 



IMPROVEMENTS IN FURNACES AND HEATERS. 



Reverberatory Furnaces. An interesting paper on this subject was re- 

 cently read by C. W. Siemens, of London, tamed for his speculations on 

 the economy of heat, before the Manchester (Eng.) Institution of Mechanical 

 Engineers. The subject, as given in a brief report, was 3, new construction 



