258 CONNECTION OF ELECTRICITY AND MAGNETISM. 



Newton himself, with that wise moderation which is characteristic of 

 all his speculations, answered that he made no pretense of explainiog 

 the mechanism by which the heavenly bodies act on each other. To 

 determine the mode in which their mutual action depends on their 

 relative position was a great step in science, and this step l^ewton 

 asserted that he had made. To explain the process by which this action 

 is effected was quite a distinct step, and this step Newton, in his Prin. 

 cipia, does not attempt to make. 



But so far was Newton from asserting that bodies really do act on 

 one another at a distance, independently of anything between them, 

 that in a letter to Bentley, which has been quoted by Faraday in this 

 place, he says : 



" It is inconceivable that inanimate brute matter should, without the 

 mediation of something else which is not material, operate upon and 

 affect other matter without mutual contact, as it must do if gravitation, 

 in the sense of Epicurus, be essential and inherent in it. That gravity 

 should be innate, inherent, and essential to matter, so that one body 

 can act upon another at a distance, through a vacuum, without the 

 mediation of anything else, by and through which their action and 

 force may be conveyed from one to another, is to me so great an absurd- 

 ity that I believe no man who has in philosophical matters a competent 

 faculty of thinking can ever fall into it." 



Accordingly, we find, in his Optical Queries and in his letters to 

 Boyle, that Newton had very early made the attempt to account for 

 gravitation by means of the pressure of a medium, and that the reason 

 he did not publish these investigations " proceeded from hence only, 

 that he found he was not able, from experiment and observation, to 

 give a satisfactory account of this medium, and the manner of its 

 operation in producing the chief phenomena of nature."* 



The doctrine of direct action at a distance cannot claim for its author 

 the discoverer of universal gravitation. It was first asserted by Eoger 

 Cotes, in his preface to the Principia, which he edited during Newton's 

 life. According to Cotes, it is by experience that we learn that all 

 bodies gravitate. We do not learn in any other way that they are 

 extended, movable, or solid. Gravitation, therefore, has as much right 

 to be considered an essential property of matter as extension, mobility, 

 or impenetrability. 



And when the Newtonian philosophy gained ground in Europe, it was 

 the opinion of Cotes rather than that of Newton that became most 

 prevalent, till at last Boscovich propounded his theory, that matter is a 

 congeries of mathematical points, each endowed with the power of 

 attracting or repelling the others according to fixed laws. In his world, 

 matter is unextended and contact impossible. He did not forget, how- 

 ever, to endow his mathematical points with inertia. In this some of 

 the modern representatives of his school have thought that he " had 



* Maclaurin's Account of Newton's Discoveries. 



