net. iv ] DISSERTATION SECOND. 123 



that gravity could not be considered as a property of mat- 

 ter; but Mr. Cotes, in the preface to the second edition 

 of the Principia, maintains, that gravity is a property which 

 we have the same right to ascribe to matter, that we have 

 to ascribe to it extension, impenetrability, or any other 

 property. This is said to have been inserted without the 

 knowledge of Newton, — a freedom which it is difficult to 

 conceive that any man could use with the author of the 

 Principia. However that be, it is certain that these diffi- 

 culties have been always felt, and had their share in re- 

 tarding the progress of the philosophy to which they seem- 

 ed to be inseparably attached. 



There were other arguments of a less abstruse nature, 

 and more immediately connected with experiment, which, 

 for a time, resisted the progress of the Newtonian philo- 

 sophy, though they contributed, in the end, very materi- 



material, operate upon and affect other matter without mutual 

 contact ; as it must do, if gravitation, in the sense of Epicurus, 

 be essential or inherent in it. That gravity should be innate, 

 inherent, and essential to matter, so that one body may act on 

 another, at a distance, through a vacuum, without the mediation 

 of any thing else, by and through which their action and force 

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

 surdity, that I believe no man who, in philosophical matters, has 

 a competent faculty of thinking, can ever fall into it." {Newtvni 

 Opera, Tom. IV. Horseley's edit. p. 438.) On this passage I 

 cannot help remarking, that it is not quite clear in what manner 

 the interposition of a material substance can convey the action of 

 distant bodies to one another. In the case of percussion or pres- 

 sure, this is indeed very intelligible, but it is by no means so in 

 the case of attraction. If two particles of matter, at opposite 

 extremities of the diameter of the earth, attract one another, this 

 effect is just as little intelligible, and the modus agendi is just as 

 mysterious, on the supposition that the whole globe of the earth 

 is interposed, as on that of nothing whatever being interposed, or 

 of a complete vacuum existing between them. It is not enough thai 

 each particle attracts that in contact with it ; it must attract the 

 particles that are distant, and the intervention of particles be- 

 tween them, does not render this at all more intelligible. 



