[ 5 10 3 
Grain of Sand :This was too light to produce any fen- 
fible Shock, and accordingly the Glafs did not break. 
In order to try further, I fhook the Glafs with the 
fmall Piece of Stone in it; and nothing following, 
I repeated the fame Experiment upon four other 
Glades, none of which broke. I then judged my 
Experiment to have fail’d, and fet by thofe five 
Glalfes; but, about half an Hour after, one of thofe 
Glades flew, and the other four foon after ; infomuch 
that the Glafs which remained the longeft entire 
broke alfo, about three Quarters of an Hour after 
its being fhook. 
Tho’ Flint is, of all the Bodies that I have em- 
ployed, that which has hitherto broken thefe Glafles 
with the greateft Eafe, it is not however the only 
Body that produces this Phenomenon, 
I let fall into one a Sapphire fet in a Ring ; and tho* 
the Bottom of the Glafs was near an Inch in Thick- 
nefs, the Sapphire palled thro’ it as thro* a Spider’s 
Web. The Glafs was difperfed on all Sides, and 
the Ring remain’d upon the Table juft where the 
Glafs refted. 
A Bit of Porcelane, of the Thick nefs of half a 
Line, and the Breadth of two Lines, broke alfo fe* 
veral Glafles; but that only fome Seconds after the 
Shock. 
A Bit of Glafs, of the fame Size, produced the 
fame Effedt ; and fo did a very fmall Pebble. 
Diamonds of feveral Sizes have conftantly done 
the fame. 
A very fmall Piece of hard-temper’d Steel has 
broken all the Glafles into which I have dropped 
it. 
One 
