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KEPOBT — 1881. 



practical considerations give us reason to hope for, we sliould still have to adjudge 

 it a wasteful though a valuable servant. Nor does there appear to be any prospect 

 of substituting with advantage any other form of thermo-dynamic engine, and 

 thus we are led to enquire wliether any other kind of energy is likely to serve us 

 better than heat, for motive power. 



Most people, especially those who are least competent to judge, look to elec- 

 tricity as the coming panacea for all mechanical deficiency, and certainly the 

 astonishing progress of electricity as applied to telegi-aphy, and to those marvellous 

 instruments of recent invention which the British Post Office claims to include in 

 its monopoly of the electric telegraph, as well as the wonderful advance which 

 electricity has made as an illuminating agent, does tend to impress us with faith in 

 its future gi'eatness in the realm of motive power as well. 



The difference between heat and electricity in their modes of mechanical action 

 is verj^ wide. Heat acts by expansion of volume which we know to be a neces- 

 sarily wastefal principle, while electricity operates by attraction and repulsion, 

 and thus produces motion in a manner wliich is subject to no greater loss of effect 

 than attends the motive action of gravity as exemplified in the ponderable applica- 

 tion of falling water in liydraulic machines. If then we could produce electricity 

 with the same facility and economy as heat, the gain would be enormous, Ijut this, 

 as yet at least, we cannot do. At present by far the cheapest method of generating 

 electricity is by the dynamic process. Instead of beginning with electricity to 

 produce power, we begin with power to produce electricity. As a secondary motor, 

 an electric engine may, and assuredly will, play an important part in future appli- 

 cations of power, but our present enquiry relates to a primary, and not a secondary, 

 employment of electricity. Thus we are brought to the question, from what 

 source, other than mechanical action, can we hope to obtain a supply of electricity 

 sufficiently cheap and abundant to enable it to take the place of heat as a motive 

 energy. It is commonly said that we know so little of the nature of electricity 

 that it is impossible to set bounds to the means of obtaining it, but ignorance is at 

 least as liable to mislead in the direction of exaggerated expectation as in that of 

 incredulity. It may be freely admitted that the nature of electricity is much less 

 understood than that of heat, but we know that the two are very nearly allied. 

 The doctrine that heat consists of internal motion of molecules may be accepted 

 with almost absolute certainty of its truth. The old idea of heat being a separate 

 entity is no longer held except by those who prefer the fallacious evidence of their 

 senses to the demonstrations of science. So also the idea of electricity having a 

 separate existence from tangible matter must be discarded, and we are justified in 

 concluding that it is merely a strained or tensional condition of the molecules of 

 matter. Although electricity is more prone to pass into heat, than heat into 

 electricitv, yet we know that they are mutually convertible. In short I need 

 scarcely remind you tliat according to that magnificent generalisation of modern 

 times, so pregnant with great consequences, and for which we are indeljted to 

 many illustrious investigators, we now know that heat, electricity, and mechanical 

 action are aU equivalent and transposable forms of energy, of which motion is 

 the essence. 



To take a cursor}' view of our available sources of energy, we have, firstly, the 

 direct heating power of the sun's rays, which as yet we have not succeeded in 

 applying to motive purposes. Secondly we have water power, wind power, and 

 tidal power, all depending upon influences lying outside of our planet. And thirdly 

 we have chemical attraction or affinity. Beyond these there is nothing worth naming. 

 Of the radiant heat of the sun I shall have to speak hereafter, and bearing in 

 mind that we are in search of electricity as a cause, and not an effect, of motive 

 power, we may pass over the dj-namical agencies comprised under the second head, 

 and direct our attention to chemical affinity as the sole remaining source of energy 

 available for our purpose. At present we derive motive power from chemical 

 attraction through the medium of heat only, and the question is, can we with 

 advantage draw upon the same source through the medium of electricity. The 

 process by which we obtain our supply of heat from the exercise of affinity is that 

 of combustion, in which the substances used consist, on the one hand, of those we 



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