THE LE SAGE THEOEY OF GRAVITATION. 



[Translation by C. G. Abbot, with, introductory note by S. P. Langley.] 

 INTRODUCTION. 



Le Sage's paper is one much oftener referred to than directly quoted 

 from or read, and this is partly because the original is very little 

 known, although it is in no more obscure a place thau the Memoirs of 

 the Berlin Academy, printed in the year 1684. 



Le Sage appears to have been one of the academicians who, though 

 in the capital of Prussia, were bound to write French of auy sort rather 

 than German, and it is only fair to the present translator to say that 

 certain passages of the original hold the meaning of the author so 

 securely hidden that it is doubtful if anyone could render them into 

 English with entire confidence that their whole meaning had been 

 grasped. Whatever the original obscurity, however, the translation, I 

 believe, means something definite and, I hope, true. 



The reader will recall that at the time when Le Sage wrote, the 

 corpuscular theory of light was universally accepted, the laws of the 

 conservation of energy and of matter were as yet unknown, and the 

 kinetic theory of gases was quite beyond the scientific horizon. Hence 

 it is a matter for surprise, not that Le Sage introduces in explanation 

 of the difficulties met with hypotheses now in a form appearing some- 

 what crude, though doubtless still conceivable, but rather that his 

 statement requires so little modification to fit it to the thought of the 

 present day. 



Some of the great objections made to Le Sage's theory, such as the 

 supposed impossibility of this shower of his atoms acting with equal 

 effect in the interior of the densest bodies as on the surface, are made 

 in probable ignorance of how entirely satisfactory the hypothesis of the 

 author is in this respect; I mean so far as the use of the mathematical 

 infinity can render it so; while other difficulties have been, if not 

 cleared up, at least rendered less formidable by the advance of modern 

 knowledge, which is on the whole clearly making more for the hypoth- 

 esis than against, if we put it in the form in which Le Sage would 

 doubtless put it were he living now. 



Thus the objection of the hypothesis of countless atoms coming from 

 and going to infinity, to the dissipation of their kinetic energy into 

 heat upon impact with solids — this latter class of objections seems to 

 have been very generally met in recent years. Thus it has been made 



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