KINETIC THEORIES OF GRAVITATION. 231 



thirty-six feet. No indications however, were perceived in the needle.* 

 Experiments with solid cylinders of copper, iron, glass, &c, secured 

 within the helix were successively made without result. Similar cyl- 

 inders were then dropped through a, fixed helix, and also reciprocating 

 motion by mechanical devices was tried, but equally without any effect 

 on the galvanometer needle. Faraday concludes, " Here end my trials 

 for the present. The results are negative. They do not shake my 

 strong feeling of the existence of a relation between gravity and elec- 

 tricity, though they give no proof that such a relation exists."! These 

 experiments were skillfully devised. to detect a correlation between the 

 two, it* any such existed. Were gravity either a form or a resultant of 

 molecular motion we should certainly expect to find evidence of an 

 expenditure of such motion, proportioned to the energy of the " fall." 



Several years later, in a memoir "On the Conservation of Force,'* 

 Professor Faraday thus states the result of his further meditations on the 

 "attractive" theme of gravitation: "I believe I represent the received 

 idea of the gravitating force aright in saying that it is a simple attractive 

 force exerted between any two or all the particles or masses of matter 

 at every sensible distance, but with a strength varying inversely as the 

 square of the distance. The usual idea of the force implies direct action 

 at a distance ; and such a view appears to present little difficulty 

 except toXewton, and a few, including inyself, who in that respect may 

 be of like mind with him.f This idea of gravity appears to me to 

 ignore entirely the principle of the conservation of force : and by the 

 terms of its definition, if taken in an absolute sense, '■varying inversely 

 as the square of the distance,' to be in direct opposition to it." § 



This singular misconception of his theme, which underlies all his 

 subsequent reasoning, may be briefly rebutted by the simple averment 

 that the conservation of force has no relation whatever to the law of 

 force, and can have no relation to it. All that the established doctrine 

 affirms, is that be the law what it may, "conservation" demands that 

 none of the resultant effects shall vanish, and that the action of the law 

 shall be absolutely the same in the same conditions. In the case of a 

 dynamic radiation — indeed, through a perfectly elastic medium, — con- 



* It is evident that whether the earth he contemplated as an electrically-charged 

 globe or as a permanent magnet, the delicate experiments of Faraday, ahove described, 

 would necessarily give indications thereof in the galvanometer : and it is an interesting 

 illustration of the scientific conscientiousness of the experimenter, to ohserve with 

 what caution these collateral results were eliminated. 



t Philosophical Transactions Roy. Soc, 1851, vol. 141, pp. 1-0. A Mr. Zalewski pre- 

 sented to the French Academy of Sciences, (April 22, and August 19, 1850, and again 

 July 5 and 19, 1852,) memoirs " On Electricity as the Cause of the Effects attrihuted to 

 Universal Gravitation." (Comptes Bendus, 1850, vol. xxx, p. 485; vol. xxxi, p. 255; 

 and for 1852, vol. xxxv, pp. 49 and 95.) "Faraday's insight was so profound, that we 

 cannot assert that something may not yet be discovered by such experiments, but it 

 will assuredly not be conservation of force." Professor Tait's Lecture on "Force," 

 Nature, 21st September, 1876, vol. xiv, p. 402. 



I Referring, of course, to the "third Bentley letter." 



$L. E. D. Phil. Mag., 1857, vol. xiii, p, 228. 



