579 
of Edinburgh, Session 1871 - 72 . 
une latitude, que les rendoit egalement compatibles avec plusieurs 
“ autres hypotheses; qu’aussi, l’on ne manqua pas de lui opposer : 
“ au lieu que, les consequences du choc des Atoms; auroient ete 
“ absolument univoques en faveur du seul principe veritable (des 
“ Accelerations egales en Tempuscules egaux).” 
If Le Sage had but excepted Kepler’s third law, it must be ad¬ 
mitted that his case, as stated above, would have been thoroughly 
established by the arguments of his “ memoire ;” for the epicurean 
assumption of parallelism adopted to suit the false idea of the earth 
being flat, prevented the discovery of the law of the inverse square 
of the distance, which the mathematicians of that day were quite 
competent to make, if the hypothesis of atoms moving in all 
directions through space, and rarely coming into collision with one 
another, had been set before them, with the problem of determin¬ 
ing the force with which the impacts would press together two 
spherical bodies, such as the earth and moon were held to be by 
some- of the contemporary philosophers to whom the epicureant 
“ would not listen.” But nothing less than direct observation, prov¬ 
ing Kepler’s third law,—G-alileo’s experiment on bodies falling from 
the tower of Pisa, Boyle’s guinea and feather experiment, and 
Newton’s experiment of the vibrations of pendulums composed of 
different kinds of substance—could give either the idea that gravity 
is proportional to mass, or prove that it is so to a high degree of 
accuracy for large bodies and small bodies, and for bodies of dif¬ 
ferent kinds of substance. Le Sage sums up his theory in an ap¬ 
pendix to the “ Lucrece Newtonien,” part of which translated 
(literally, except a few sentences which I have paraphrased) is as 
follows:— 
Constitution of Heavy Bodies. 
1st, Their indivisible particles are cages; for example, empty 
cubes or octahedrons vacant of matter except along the twelve edges. 
2d, The diameters of the bars of these cages, supposed increased 
each by an amount equal to the diameter of one of the gravific 
corpuscles, are so small relatively to the mutual distance of the 
parallel bars of each cage, that the terrestrial globe does not inter¬ 
cept even so much as a ten-thousandth part of the corpuscules 
which offer to traverse it. 
