figure by vertue of their fpringipefs after they have been a 
little imprefled upon* 
Befides, he takes notice, on this occafion, of an Expenmenr, 
which fecms ftrongly to fupport his fentiment^which is, That if 
you let fall upon a great flat and polifb't Stone a Ball of Clay 
pretty fofc, from the height of 12 or 15 inches, putting a little 
paper or linnen rag on the place where the faid ball is to touch 
the (lone,that fo it may not ftick to iCjic will not remount at all^ 
orvery Httle: But if you let Ml upon the fame ftoneaBall 
full of comprefled Air , you will fee that part , by which it 
touches the ftone, flattened like the ball of foft earth ; but this 
imprefljon fully reftoring it felf, the ball will remount very 
high, and it would fly up higher, if the Air , which refifts much 
more to a very large and very light body , than to a fmall and 
very ponderous one^ did not flop a confiderable pare of its ve- 
locity, as well io defcendingas afcending. 
Whence, and from other Reafons and Experiments , by him 
delivered, ht concludes, that the greateft part of hard bodies, 
as &teelyMaryieiGlafi^lv0rfjJaJp€r^ &c. have a ready and ftrong 
fpringy power ; and that all the motions of refleSing bodies 
I are only made by fprings. Whereunto he adds, that if it ILouJd 
|| be fuppofed that hard bodies are inflexible , it would be im- 
poflible to explicate their motions when their weights are un- 
equal, and that the phaenomena do no ways agree to fuchan 
bypoihefis. But taking k for ameer Hypothefis, what he pre- 
tends to have demonftrated concerning the Springioefs of Hard 
bodies, he tells us, that by that means all motionSjbefalling 
thofe bodies, afier they have any way impelled one another, 
may eafily be accounted for. And he is perfwaded , that this 
truth may eafily be fecn by a great number of Propofitions^ 
whicbheadvanceth in this Book , of which the Demonftrati- 
ons agree very well with the Experiments. 
i 
