577 
of Edinburgh, Session 1871-72. 
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 Bumford* in the 
following statements : — 
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. And this is the reason why I desired you would 
“ not ascribe innate gravity to me. That gravity should be innate, 
u inherent, arid essential to matter, so that one body may act upon 
11 another at a distance through a vacuum , without the mediation 
“ of anything else, by and through which their action and force 
u 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 Ihnen nicht bergen, dass ich iiber diese Puncte ein volliger 
“ Newtonianer bin, und verwundere ich mich, dass Sie den Principiis 
“ Cartesianis so lang adhariren ; es mochte wohl einige Passion vielleicht 
“ mit unterlaufen. Hat Oott konnen eine animam, deren Natur uns unbe- 
“ greiflich ist, erschaffen, 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 H 
VOL. VII. 
