PROPERTIES OF GLASS. 157 



of commerce was first established in Lancashire, about the year 

 1773, through the spirited exertions of a very respectable body of 

 proprietors, who were incorporated by an act of parliament. 

 From those various difficulties constantly attendant upon new un- 

 dertakings, when they have to contend with powerful foreign 

 establishments, it has not, however, been conducted with any 

 great degree of success. 



SECTION II. 



Properties of Glass. 



THE properties of glass are highly interesting and remarkable. 

 The following are among the most curious. 



1. Glass is one of the most elastic bodies in nature. If the 

 force with which glass balls strike each other be reckoned sixteen, 

 that wherewith they recede by virtue of their elasticity will be 

 nearly fifteen. 



2. When glass is suddenly cooled, it becomes exceedingly brit- 

 tle ; and this britfleness is sometimes attended with very surprising 

 phenomena. Hollow bells made of annealed glass, with a small 

 hole in them, will fly to pieces by the heat of the hand only, if 

 the hole by which the internal and external air communicate be 

 stopped with a finger. Lately, however, some vessels made of 

 such annealed glass have been discovered, which have the remark, 

 able property of resisting very hard strokes given from without, 

 though they shiver to pieces by the shocks received from the fall 

 of very light and minute bodies dropped into their cavities. These 

 glasses may be made of any shape ; all that need be observed in 

 making them is, that their bottom be thicker than their sides. 

 The thicker the bottom is, the easier do the glasses break. One 

 whose bottom is three fingers breadth in thickness flies with as 

 much ease at least as the thinnest glass. Some of these vessels 

 have been tried with strokes of a mallet sufficient to drive a nail 

 into wood tolerably hard, and have held good without breaking. 

 They have also resisted the shock of several heavy bodies let fall 

 into their cavities, from the height of two or three feet ; as musket- 

 balls, pieces of iron or other metal, pyrites, jasper, wood, bone, 

 &c. But this is not surprising, as other glasses of the same shape 

 and size will do the same : bnt the wonder is, that taking a shiver 

 of flint of the size of a small pea, and letting it fall into the glas 

 only from the height of three inches, in about two seconds the 



