I^i PHILOSOPHICAL TRANSACTIONS. [aNNO 1745. 



tliem on a down pillow, and putting them in water; in all which cases they broke 

 in the very same manner. He then half filled one of them with water, and a 

 piece of flint, about the size of a pea, broke it. 



All the bodies with which he had yet broken glasses having been elastic without 

 being ductile, he was willing to inquire if those qualities were essentially neces- 

 sary, though he was already satisfied that all the bodies that had those qualities, 

 such as ivory, for example, would not produce the effect. After many trials, 

 none of which succeeded, he thought of slightly rubbing the bottoms of some of 

 the glasses with his finger, and all those on which he made that experiment 

 broke, though some of them did not fly till about half an hour after they had 

 been so rubbed. Thinking, that perhaps the heat he communicated to them 

 with his hand might occasion their breaking, he poured into several some almost 

 boiling water, which certainly gave them a much greater heat than he could 

 have given them with his hand; but none of those glasses broke. 



He found in the animal kingdom only one sort of bodies capable of breaking 

 these glasses, which are pearls: he dropped one of near a line diameter into a 

 glass, which broke in about half an hour. 



Though the experiment of rubbing with the finger had convinced him that 

 the stroke or shock of a falling body is not always necessary to break these 

 phials, he thought of scratching with a flint the bottom of the glass, and it im- 

 mediately broke. To assure himself whether the scratch he had made was the 

 occasion of its breaking, he took a rod of iron having a rounded end ; he pushed 

 it strongly against the bottom of the glass, and the glass flew. He then did 

 the same, and even pushed much harder, against the bottoms of several ordinary 

 glasses, but without any effect ; for though these glasses were much thinner than 

 the others, yet none of them broke. 



If the glasses in question are every where extremely thin, they do not break in 

 the circumstances abovementioned, he frequently dropped into such glasses the 

 same sorts of bodies as had broken the thicker ones, but without any success. 

 He only met with one that split, and he was not even sure but that the weight 

 of the body dropped into it, which was a stone of some size, might occasion its 

 breaking. 



All the phials on which he made these experiments were of white glass ; he had 

 not an opportunity of trying those made with the green. 



The author of the dissertation, published at Padua on this subject, pretends to 

 account for all these singular phenomena by saying, that the bodies dropped into 

 these phials cause a concussion that is stronger than the cohesion of the parts of 

 the glass; and that consequently, a rupture of the same must ensue. But why 

 does not a ball of gold, silver, iron, copper, or any of the other bodies that 

 have been tried unsuccessfully, though 1000 times heavier, equally cause thi» 



