Corpuscules of Le Sage, 325 



Conception, which facilitates the application of Mathematics to 

 determine the mutual Influence of these Heavy Bodies, and 

 these Corpuscules. 



1st. Decompose all heavy bodies into molecules of equal mass, 

 so small that they may be treated as attractive points with respect 

 to theories in which gravity is considered without reference to 

 its cause ; that is to say, each must be so small that inequalities 

 of distance and differences of direction between its particles and 

 those of another molecule, conceived as attracting it and being 

 attracted by it, may be neglected. For example, suppose the 

 diameter of the molecule considered to be a hundred thousand 

 times smaller than the distance between two bodies of which the 

 mutual gravitation is examined, which would make its apparent 

 semidiameter, as seen from the other body, about one second 

 of angle. 



2nd. For the surfaces of such a molecule, accessible but im- 

 permeable to the gravific fluid, substitute one single spherical 

 surface equal to their sum. 



3rd. Divide those surfaces into facets small enough to allow 

 them to be treated as planes, without sensible error [&c. &c] . 



Remarks. 



It is not necessary to be very skilful to deduce from these 

 suppositions all the laws of gravity, both sublunary and universal 

 (and consequently also those of Kepler, &c), with all the accuracy 

 with which observed phenomena have proved those laws. Those 

 laws, therefore, are inevitable consequences of the supposed con- 

 stitutions. 



2nd. Although I here present these constitutions crudely and 

 without proof, as if they were gratuitous hypotheses and hazarded 

 fictions, equitable readers will understand that on my own part 

 I have at least some presumptions in their favour (independent 

 of their perfect agreement with so many phenomena), but that 

 the development of my reasons would be too long to find a place 

 in the present statement, which may be regarded as a publication 

 of theorems without their demonstrations. 



3rd There are details upon which I have wished 



to enter on account of the novelty of the doctrine, and which 

 will readily be supplied by those who study it in a favourable 

 and attentive spirit. If the authors who write on hydrodyna- 

 mics, aerostatics, or optics had to deal with captious readers, 

 doubting the very existence of water, or air, or light, and there- 

 fore not adapting themselves to any tacit supposition regarding 

 equivalencies or compensations not expressly mentioned in their 

 treatises, they would be obliged to load their definitions with a 



