I IO The consequences of the

the resistance these parts would make by then*vis inertia , to be simply moved, if they wereseparated. And it is to be observed in this ar-gument, that any finite force will move anyassigned body with some velocity; for in theshock of unelastick bodies, the velocity ofboth after the congress, is to the velocity ofthe impinging body before, as the impingingbody is to the sum of both bodies: where-fore as long as the impinging body bears anyratio to the quiescent one, the velocity afterthe impact will always be something. Fromthis we may be helped to estimate, or con-ceive, how many thousand, nay millions oftimes, the resistance of matter is greater fromthis external impulse of cohesion, than fromits own natural inactivity: and that not onlyin hard bodies, but in the elements or con-stituent parts of all bodies j as will appearas we go on.

IX. This impulse, or mutual attraction*for it is the same thing which we name it*since we must conceive it external to matter(r) is called by philosophers the attraction of

cohesion*

(r) s’Gravefande, speaking of this very attractioncohesion, defines it thus: Per vocem attradtionU intelli£ f