of Edinburgh, Session 1871-72. 
577 
no other ultimate properties of matter than perfect fluidity and in¬ 
compressibility are noticed, and shown to be, in all probability, 
only dependent on the weakness of mathematics. 
3. On the Ultramundane Corpuscules of Le Sage. 
By Professor Sir W. Thomson. 
(Abstract.) 
Le Sage, born at Geneva in 1724, devoted the last sixty-three 
years of a life of eighty to the investigation of a mechanical theory 
of gravitation. The probable existence of a gravific mechanism is 
admitted and the importance of the object to which Le Sage 
devoted his life pointed out, by Newton and Bum ford* in the 
following statements:— 
“ It is inconceivable that inanimate brute matter should, without 
“ the mediation of something else, which is not material, operate 
u 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. And this is the reason why I desired you would 
“ not ascribe innate gravity to me. That gravity should be innate, 
‘ c inherent, and essential to matter, so that one body may 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 
“ absurdity, that I believe no man who has in philosophical 
“ matters a competent faculty of thinking, can ever fall into it, 
* On the other hand, by the middle of last century the mathematical 
naturalists of the Continent, after half a century of resistance to the Newtonian 
principles (which, both by them and by the English followers of Newton, were 
commonly supposed to mean the recognition of gravity as a force acting 
simply at a distance without mediation of intervening matter), had begun to 
become more “Newtonian” than Newton himself. On the 4th February 
1744, Daniel Bernoulli wrote as follows to Euler, “ Uebrigens glaube ich, 
“ dass der Aether sowohl gravis versus solem. als die Luft versus terrain 
“ sey, und kann Ilmen nicht bergen, dass ich fiber diese Puncte ein volliger 
“ Newtonianer bin, und verwundere ich mich, dass Sie den Principiis 
“ Oartesianis so lang adhariren ; es mochte wohl einige Passion vielleicht 
“ mit unterlaufen. Hat Gott konnen eine animam, deren Natur uns unbe- 
“ greiflich ist, erscliaffen, so hat er auch konnen eine attractionem universalem 
“ materise imprimiren, wenn gleich solche attractio supra captum ist, da 
“ hingegen die Principia Cartesiana allzeit contra captum etwas involviren.” 
4 ii 
VOL. VII. 
