32 PROCEEDINGS OF THE 



theory and practice have demonstrated that its meebanical application does nofc 

 involve so much waste of power as takes place in a steam-engine ; but whether 

 we use heat or electricity as a motive power, we must equally depend upon 

 chemical affinity as the source of supply. The act of uniting to form a chemical 

 product liberates an energy which assumes the form of heat or electricity, from 

 either of which states it is convertible into mechanical effect. In contemplating, 

 therefore, the application of electricity as a motive power, we must bear in mind 

 that we shall still require to effect chemical combinations, and in so doing to con- 

 sume materials. But where are we to find materials so economical for this 

 purpose as the coal we derive from the earth and the oxygen we obtain from the 

 air ! The latter costs absolutely nothing ; and every pound of coal, which in the 

 act of combustion enters into chemical combination, renders more than two-and-a- 

 half pounds of oxygen available for power. "We cannot look to water as a prac- 

 tical source of oxygen, for there it exists in the combined state, requiring expen- 

 diture of chemical energy for its separation from hydrogen. It is in the atmos- 

 phere alone that it can be found in that free state in which we require it, and 

 there does not appear to me to be the remotest chance, in an economic point of 

 Tiew, of being able to dispense with the oxygen of the air as a source either of 

 thermo-dynamic or electro-dynamic effect. But to use this oxygen we must 

 consume some oxidiEable substance, and coal is the cheapest we can procure. 



I have hitherto spoken of coal only as a source of mechanical power, but it is 

 also extensively used for the kindred purpose of relaxing those cohesive forces 

 Tvhich resist our efforts to give new forms and conditions to solid substances. In 

 these applications, which are generally of a metallurgical nature, the same 

 wasteful expenditure of fuel is everywhere observable. In an ordinary furnace 

 employed to fuse or soften any solid substance, it is the excess of the heat of 

 combustion over that of the body heated which alone is rendered available for 

 the purpose intended. The rest of the heat, which in many instances constitutes 

 by far the greater proportion of the whole, is allowed to escape uselessly into the 

 chimney. The combustion also in comnjon furnaces is so imperfect, that clouds 

 of powdered carbon, in the form of smoke, envelope our manufacturing towns, 

 and gases, which ought to be completely oxygenized in the fire, pass into the air 

 with two-thirds of their heating power undeveloped. 



Some remedy for this state of things, we may hope, is at hand, in the gas 

 regenerative furnaces recently introduced by Mr. Siemens. In these furnaces the 

 rejected heat is arrested by a so-called "regenerator," as in Stirling's air-engine, 

 and is communicated to the new fuel before it enters the furnace. The fuel, 

 however, is not solid coal, but gas previously evolved from coal. A. stream of 

 this gas raised to a high temperature by the rejected heat of combustion is 

 admitted into the furnace, and there meets a stream of atmospheric air also raised 

 to a high temperature by the same agency. In the combination which then 

 ensues, the heat evolved by the combustion is superadded to the heat previously 

 acquired by the gases. Thus, in addition to the advantage of economy, a greater 

 intensity of heat is attained than by the combustion of unheated fuel. In fact, as 

 the heat evolved in the furnace, or so much of it as is not communicated to the 

 bodies exposed to its action, continually returns to augment the effect of the new 



