Mr. W. J. ]\Iacquorx Ranking on the Science of Energetics. 385 



the fact of the production of heat by friction, the basis of the true theory 

 of heat, was long neglected, because inconsistent with the hypothesis of 

 caloric ; and the fact of the production of cold by electric currents, at 

 certain metallic junctions, the key (as Professor William Thomson recently 

 showed) to the true theory of the phenomena of thermo-electricity, was, 

 from inconsistency with prevalent assumptions respecting the so-called 

 "electric fluid," by some regarded as a thing to be explained away, and 

 by others as a delusion. 



Such are the evils which arise from the misuse of hypothesis. 



VI. Advantages of an Extension of the Abstractive Method 

 or Fbaming Theories. 



Besides the perfecting of Mechanical Hypotheses, another and an en- 

 tirely distinct method presents itself for combining the physical sciences 

 into one system ; and that it is by an extension of the Absteactive Pko- 

 CESS in framing Theories. 



The abstractive method has already been partially applied, and with 

 success, to special branches of molecular physics, such as heat, electricity, 

 and magnetism. We are now to consider in what manner it is to be 

 applied to physics generally, considered as one science. 



Instead of supposing the various classes of physical phenomena to be 

 constituted in an occult way of modifications of motion and force, let us 

 distinguish the properties which those classes possess in common with 

 each other, and so define more extensive classes denoted by suitable 

 terms. For axioms, to express the laws of those more extensive classes 

 of phenomena, let us frame propositions comprehending as particular 

 cases, the laws of the particular classes of phenomena comprehended 

 under the more extensive classes. So shall we arrive at a body of prin- 

 ciples, applicable to physical phenomena in general, and which being 

 framed by induction from fjicts alone, will be free from the uncertainty 

 which must always attach even to those mechanical hypotheses whose 

 consequences are most fully confirmed by experiment. 



This extension of the abstractive process is not proposed in order to 

 supersede the hypothetical method of theorizing ; for in almost every 

 branch of molecular physics it may be held, that a hypothetical theory 

 is necessary as a preliminary step to reduce the expression of the phe- 

 nomena to simplicity and order, before it is possible to make any pro- 

 gress in framing an abstractive theory. 



VII. Nature of the Science of Energetics. 



Energy, or the capacity to effect changes, is the common character- 

 istic of the various states of matter to which the several branches of 



