420 PHILOSOPHICAL TRANSACTIONS. [aNNO ]708. 



Theorem Q. — If any corpuscle be in contact with a body ; the force by which 

 that corpuscle is attracted, that is, the force by which it coheres with that body, 

 will be proportional to the quantity of contact : for the parts more remote from 

 the contact, contribute nothing to the cohesion. Therefore, according to the 

 various contact of particles, various degrees of cohesion arise ; and the force of 

 cohesion is greatest, when the superficies, where bodies touch each other, are 

 planes; in which case, caeteris paribus, the force with which a corpuscle coheres 

 with other corpuscles, will be as the parts of the superficies that touch each 

 other: hence appears the reason why two marbles, exactly polished, and touch- 

 ing each other in their plain superficies, cannot be separated, but by a weight 

 that far exceeds the gravity of the incumbent atmosphere: hence likewise may 

 be given the solution of that noted problem, the cohesion of matter. 



Theorem 10. — ^Those corpuscles are most easily separated from each other, 

 which have the fewest and smallest points of contact with other corpuscles; as 

 is the case in spherical corpuscles infinitely small. — Hence fluidity is accounted 

 for. 



Theorem 1 1 . — The force by which any corpuscle is attracted towards another 

 body very near it, does not change its quantity, whether the matter of the at- 

 tracting body be increased or diminished; the density of the body, and the 

 distance of the corpuscle remaining the same. — For, since the attractive force 

 of particles extends only to very small distances; it is plain that the more re- 

 mote particles at c, d, and e, (plate 10, fig. 21) contribute nothing to attract 

 the corpuscle a: therefore the corpuscle will be attracted with the same force 

 towards b, whether these be present or removed, or whether others be added 

 to them. 



Theorem 1 2. — If the contexture of any body be such, as that the particles of 

 the last composition should by some external force (such as the pressure of a 

 weight, or the stroke of any other body) be removed a little from their primo- 

 genial contacts, but so as not to acquire new contacts; the particles mutually 

 attracting each other will soon return to their primogenial contacts; and the 

 same contacts and positions of the particles that constitute any body, being re- 

 stored, there will also be a restitution of the same figure of that body: conse- 

 quently bodies may by their attractive force again recover their pristine figures. 

 Hence we may account for elasticity : for, as bodies impinging on each other, 

 do by their elastic force recede from each other, as is demonstrated in the 

 physical lectures; so the resilition of bodies from each other should arise from 

 their attracting force. 



Theorem 13. — But if the texture of a body be such, as that its particles, 

 when removed from their primogenial contacts by a force impressed on them, 



