PAST CHANGES IN THE UNIVERSE. 



355 



done in friction, as in dragging masses (vehicles, 

 etc.) along the earth's surface, then the waves of 

 heat due to the friction are radiated into the me- 

 dia of space, and, becoming naturally dissipated 

 in the gravific medium through which they have 

 to pass, the energy thus finally returns to this 

 medium, to be available for utilization again. 

 Winds or currents of air are due directly (as is 

 known) to variations of pressure in the earth's 

 atmosphere, which readjust themselves through 

 the action of gravity. The gravific medium is 

 therefore the agent directly concerned in pro- 

 ducing the current of air or wind, and therefore 

 is the motive agent concerned in developing mo- 

 tion in the machinery driven through the inter- 

 vention of the wind. In the case of the ship pro- 

 pelled by the wind, the power is converted into 

 heat in the passage of the ship through the water. 

 The heat then passes in waves to the media in 

 space, or is dissipated in the source whence it 

 was derived in a cyclical process. It should be 

 observed that all these deductions are necessa- 

 rily true on the acceptance of the explanation of 

 the mechanism of gravity afforded by the physi- 

 cal theory. 



There can be little doubt that the explanation 

 of gravity (the fundamental agency in Nature) 

 will naturally and inevitably entail with it, in 

 principle, analogous explanations of the other 

 molecular motions (" chemical " reactions, etc.). 

 Thus the operation of the steam-engine will show 

 itself as a cyclical process, the motion passing 

 from the media in space to the coal, and thence 

 (in a circle) to the media in space in the various 

 operations of the engine. 1 Thus considerations 

 of great practical interest present themselves on 

 the recognition of the existence of the stores of 

 concealed motion in space revealed by the ki- 

 netic theory of gravitation, and problems of the 

 highest practical importance may suggest them- 

 selves as to possible methods of utilizing this 

 store of motion to greater advantage than at pres- 

 ent. There might be a tendency to regard con- 

 siderations of this nature (independently of their 

 truth or error) as in some degree occult. This 

 could only arise from the kind of prejudice that 

 tends to beset every new path, or possibly in the 

 absence of realization of the mechanical fitness of 

 the scheme due to attention not having been given 

 to the subject. What may be justly regarded as 

 occult are the effects themselves (or the devel- 



1 See also a paper in the Philosophical Magazine 

 for April last (" The Bearing of the Kinetic Theory 

 of Gravitation on the Phenomena of 'Cohesion' and 

 ' Chemical Action ' "). 



opments of motion in matter, occurring on every 

 hand) without any explanation at all. Since the 

 store of energy simply consists of finely-subdi- 

 vided matter in a state of rapid motion, and 

 since it is obviously just as easy to reason of 

 matter of one dimension as of another, there can 

 be nothing whatever occult about the subject at 

 all. The conclusion deducible with certainty be- 

 forehand that this store of motion — if it did ex- 

 ist in space — would be concealed, ought to go far 

 to remove all preliminary doubts es to its exist- 

 ence ; and unless we are ready to surrender the 

 right of using our reason, the developments of 

 motion occurring on all sides (as combustion, 

 the detonation of explosives, and the varied move- 

 ments developed in masses and molecules of 

 matter, etc.) are utterly inexplicable without the 

 existence of this store of motion in space. Mi- 

 nuteness of size of the particles is evidently 

 adapted to rapidity of motion, and this rapidity 

 of motion is itself essential to an intense store 

 of energy, and this rapidity of motion, combined 

 with minuteness of size, obviously and necessa- 

 rily renders the motion of the particles concealed ; 

 indeed, the more perfect the concealment the 

 higher should we be warranted in estimating 

 the intensity of the store of energy to be (from 

 the known fact that the higher the velocity of 

 the component particles, the more impalpable does 

 the medium become). It is very important, there- 

 fore, to keep in view that — independently of all 

 question of the existence of this store of energy 

 in space — it is so fan an indisputable fact that if 

 it did exist it would be perfectly concealed. There 

 can therefore be no legal a priori reason for 

 doubting its existence, and the admirable man- 

 ner in which (on analysis) the mechanical con- 

 ditions show themselves to be adapted to allow 

 the existence of an available store of energy in 

 space, to any intensity consistent with conceal- 

 ment, and in harmony with the conditions of life, 

 ought to render the contemplation of the problem 

 one of great mechanical interest. Surely, for ex- 

 ample, to realize how the motion is transferred 

 from the concealed store of motion in space to a 

 mass of gunpowder (as a shell, for instance) in 

 the act of explosion, is a problem of the highest 

 mechanical interest, and no one surely would mis- 

 take theories which may serve as a convenient 

 temporary refuge in the absence of any concep- 

 tion of the process involved, as explanations of 

 the process involved. Clearness of conception is 

 the test of truth, and constitutes the real dignity 

 of Science, and theories, however elaborated, if 

 vague, have no real dignity; and the aim ought 



