and the Molecular Energy of Matter. 87 



result, so if we introduce assumed facts in explaining a 

 known fact, there is in effect no explanation given. 



But the internal energy of matter due to the motion of 

 its molecules, is at present a well-established fact, and is free 

 from the objection of being an hypothetical existence as- 

 sumed for the purpose of explaining a known fact. 



The case then may be stated thus : When two bodies are 

 placed near one another and left to themselves, each acquires 

 a certain energy. This must have been derived from some 

 antecedent energy ; but the only antecedent energy known 

 to exist is that due to molecular motion. Hence we shall be 

 justified in turning our investigations, whether experimental 

 or mathematical, in that direction. 



This is an explanation which has not been possible until 

 within late years. Newton never dreamt that what we call 

 inanimate matter is in reality animated by vast energies ; 

 had he known this fact he would perhaps not have 

 regarded it as an absurdity that two such bodies should 

 exert forces upon one another. 



That gravitation is due to molecular energy is also the 

 result of the following consideration drawn from the analogy 

 between gravitation and the forces of magnetism and elec- 

 tricity. These three forces are the only known forms of 

 attraction at sensible distances. They differ among them- 

 selves in many respects, but they are, in their main features, 

 so similar as to form a class very distinctly marked off from 

 all other existences. Now it is certain that magnetism and 

 electricity are caused in some unknown manner by the 

 energy of material molecules. But when the forms of energy 

 are absent to which these two kinds of attraction are pecu- 

 liarly due, the portions of matter in question are still 

 endued with the other forms of molecular motion, and are 

 still found to possess a power of attraction similar to, 

 though much less intense than, the other attractions. Is 

 there not a large measure of probability in the belief that 

 also in the case of this universal form of attraction, the force 

 is due to the universal form of molecular energy ? 



A more definite idea of Avhat is meant will perhaps be 

 obtained in this way : — When an electro-magnet attracts a 

 piece of iron in front of it the following action goes on : — 

 Molecular vibrations are originated in the batteiy and pass 

 into the core of the magnet. From this core they are pro- 

 pagated out into space in the form of waves, and, in some 



