VOL. XLIII.] PHILOSOPHICAL TRANSACTIONS. l63 



shock, of several heavy bodies, that are let fall into their cavities. Thus he has 

 dropped, from the height of 2 or 3 feet, musket balls, pieces of iron, brass, tin, 

 silver, gold, antimony, bismuth, pyrites, jasper, and several sorts of woods, 

 ivory, and bone; all which is indeed nowise extraordinary; for other glasses 

 equally thick would also bear the strokes of the same bodies, but herein consists 

 what is more surprising. 



He took a shiver of flint, of the size of a small pea; and let it fall into the 

 glass, from the height of 3 inches, and in about 2 seconds the glass flew. 

 Having repeated the same experiment on several other glasses with the same 

 piece of flint, the greatest part broke in the moment of the shock, and the 

 others 1 or 2 seconds after it. 



He let fall into different glasses a shiver of flint, of but half the size of that 

 used in the former experiment, and the glasses flew in the same manner. An- 

 other bit of flint, of the size of a small lentil, also produced the same effect. 



Being encouraged with this success, he let fall into one of his glasses a piece 

 of flint no larger than a grain of sand : this was too light to produce any sensible 

 shock, and accordingly the glass did not break. In order to try further, he shook 

 the glass with the small piece of stone in it ; and nothing following, he repeated 

 the same experiment on 4 other glasses, none of which broke. He then judged 

 the experiment to have failed, and set aside those 5 glasses; but, about half an 

 hour after, one of the glasses flew, and the other four soon after; insomuch that 

 the glass which remained the longest entire, broke also, about 3 quarters of an 

 hour after its being shook. 



Though flint is, of all the bodies that he had employed, that which has 

 hitherto broken these glasses with the greatest ease, it is not however the only 

 body that produces this phenomenon. He let fall into one a sapphire set in a 

 ring; and though the bottom of the glass was near an inch in thickness, the 

 sapphire passed through it as through a spider's web. The glass was dispersed 



on all sides, and the ring remained on the table just where the glass rested. 



A bit of porcelain, of the thickness of half a line, and the breadth of 2 lines, 

 broke also several glasses; but that only some seconds after the shock. — A bit 

 of glass of the same size, produced the same effect ; and so did a very small 

 pebble. — Diamonds of several sizes have constantly done the same. — A very small 

 piece of hard tempered steel has broken all the glasses into which he dropped it. 

 — One of those pellets also that boys play with, and which they commonly call 

 marbles, broke a glass into which it was dropped, but not till 4 minutes after 

 its fall. 



Being desirous to know if the bodies, on which the glasses rested, contributed 

 any thing to the ease of their breaking, Mr. A. repeated the same experiments, 

 holding the glasses in his hand, and setting them upright in clay, and placing 



