THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



FEBRUAR Y 1895. 



XIY. Comparative Review of some Dynamical Theories of 

 Gravitation. By Dr. S. Tolver Preston*. 



Introduction. 



THE modes of accounting for natural phenomena have been 

 very different at different times. The old philosophers 

 had in general scarcely an idea of that which we now call a 

 mechanical explanation; they figured to themselves rather 

 the agencies working in nature as living beings. This applies 

 also to Kepler, who banished from himself any idea of a 

 mechanical explanation of the laws discovered by him. On 

 the basis of the researches of Galileo, Newton was the founder 

 of the Mechanics of to-day ; and on his principles the edifice 

 of the action-at-a-distance theory has been founded. Until 

 Newton's time the notion of a direct action at a distance was 

 completely unknown : on the contrary, many experiments 

 exist by the Greek philosophers to account for the seeming 

 action at a distance by the intervention of a medium ; there- 

 fore Demokritos sought to explain natural phenomena by the 

 motions of very fine bodies. First Boscovich, Mosotti, 

 Wilhelm Weber, and many others developed the aspect of 

 nature on the basis laid down by Newton, in accordance with 

 which the universe consists of a number (if even very great) 



* Being a Dissertation presented to the Philosophical Faculty of the 

 University of Munich, for the attainment of the degree of Doctor of 

 Philosophy (translated from the German). Communicated by the Author 



Phil. Mag. S. 5. Vol. 39. No. 237. Feb. 1895. L 



