4 -

A V IS INERTIAE

III. The body A makes a Certain resistancebefore it can be moved with a velocity as C;for otherwise the force would not be neces-sary, if, to wit, it did not make this certaindegree of resistance to render it necessary.And it makes double that resistance, beforeit can be moved with a velocity as 2 C; andtriple that resistance to be moved with a velo-city as 3 C, &c. still for the fame reason. Andit makes but one half the first resistance, to bemoved with the velocity ~ C; and but onethird of it, to be moved with the velocity ~ C,and to be moved with the velocity as o C,that is to rest still, it makes no resistance at all.

IV. Or, if instead of different celerities,as in N° 2 and 3, we take the quantity ofmatter different, the appearance is equallyconstant, and certain (from experience, atleast) and the consequence of it the same.For the body A requires a certain force to beimpressed upon it, to be moved with a cele-rity as C; or such a force is necessary: andtherefore it makes a certain resistance to bemoved with this celerity, otherwise the forcewould not be necesiary. And a body as 2 Ajvill require twice that force to be impresied

upon