254 THOUGHTS ON THE NATURE AND ORIGIN OF FORCE. 



matliematical theory of lij-drodynamics,) thiulis he finds iu these phe- 

 nomena an explanation of force in general, inclnding that of gravitation. 

 He observes : " In mechanics — in nature, there is no such thing as a 

 pulling force. * * * The line of conclusions here indicated tends to 

 argue that there is no such thing as attraction in the sense of a pull- 

 ing force, and that two utterly isolated bodies cannot influence one 

 another. If the ethereal vibrations which are supposed to constitute 

 radiant heat, resemble the aerial vibrations which constitute radiant 

 sound, the heat which allbodiespossess, and which they are all supposedto 

 radiate in exchange, will cause all bodies to be urged toward one another."* 

 Supposing that such resulting ethereal currents could have any sen- 

 sible influence on planetary masses, it seems to be entirely overlooked 

 that such currents would be of the most variable and fitful character. 

 Every sun-spot would derange the planetary orbits; jDlanets when cloud- 

 clad would affect eacli other very differently from those having trans- 

 parent or diathermanous atmospheres ; and no resource of mathematics 

 could ever predict an occultation or eclipse. 



Were it necessary to discuss the question whether gravitation is 

 either a form or a result of motion, the fact that its action is instanta- 

 neous, that it requires no sensible lapse of time to be felt by the most 

 distant planet, is perhaps the most direct evidence bearing on the point. 

 Were any interval of time occupied in the transmission of this influence 

 from the sun to a planet, there would result a phenomenon of " aberra- 

 tion" (similar to that of light) by the amount of orbital motion occur- 

 ring during the time of its transit, the consequence of which would be 

 an acceleration and extension of the radius- vector, or a spiral unwinding 

 and final dispersion of all the planets and their satellites. In general 

 terms, the stability of a planetary system, or the conservation of mean 

 distances, depends upon the absolutely radial and immediate action 

 of the central attraction. Sui^posing, in the case of our earth, that 

 gravity occupied even so short a time as the hundredth part of one second 

 in passing over the ninety-one and a half million miles from the sun — dur- 

 ing this interval (of the one-hundredth of a second) the planet would 

 have traveled about one thousand feet in its orbit; and the resulting dis- 

 placemeut or " aberration'' of directive force would be about the twenty- 

 five-hundredth part of one second of orbital arc. It has been shown 

 that even this small deviation would have been noticeable in the 

 two thousand years separating us from the time of Hipparchus. Arago 

 has estimated that any possible velocltt/ of gravitation must be, at least, 

 fifty million times that of light !t 



Gravitation, therefore, is not a motion ; nor is it the product of any 

 motion. We are forced to the conclusion, however " unable to conceive" 

 the fact, that it is really an actio in dlstans, and that ad infinitum ; that 

 it is a force, a ftiint reflex of its Author, Instantaneously omnipresent. 



* L. E. D. Phil. Mag. for November, 1870, Vol. XL, p. 354 ; ami Juno, 1871, Vol. XLI, 

 p. 406. 



t Popular Adrononvj, English edition, Vol. II, p. 469. 



