inaEHvity of Matter, & c . $9

tity of motion in itself, without a foreigncause, an immaterial Power! And yet rightlyconsidered, this is not more wonderful, thanthat a stone, as soon as one lets it go, shouldbegin to move to the earth, and still rushforward with a greater and greater rapidity.

If this last motion were seen but rarely, theschools of philosophers would have been fullof it: nor is there any one so little curious,who would not go far to fee such a rarefight, if it happened but once a year. Butthe mere difference of happening frequentlyor seldom cannot change the nature of athing truly wonderful in itself. The con-stancy of an appearance is not a mark ofthe fatal neceflity of it; but of the goodnessc>f that Being who makes it constant for ourbenefit; which is the present cafe, as wassaid above, N° 25. of the last section.

IV. As elasticity in general hath somethingvery surprizing in it, so that of the air de-serves our particular notice. What is calledelasticity, or spring in the air, is only a re-pulsive force exerted between its particles (e).

For

(e) See s’Gravesande s IntruluEl, ad Phil. Newton.h 2. c. 13. Experiment .3. and the reasoning upon so

where