562 THE POPULAR SCIENCE MONTHLY. 



glass can be cut through with the diamond, and as, moreover, its sur- 

 face can be removed by polishing and cutting with the wheel, without 

 injury to the mass, it is evident that it must exist under conditions 

 very dissimilar from those of a Rupert's drop. Moreover, melted 

 glass, on being dropped into De la Bastie's bath, gives a similarly 

 shaped body, from which the tail can be broken off, piece by piece, 

 without injury to the body, which can be scratched, knocked and 

 thrown about, without exhibiting any signs of deterioration. Bearing 

 upon this point, too, comes the fact that toughened glass can be ele- 

 gantly engraved, either by Tilghman's sand-blast process, or by means 

 of hydrofluoric acid, in the ordinary way, the surface or outer skin 

 being thus removed. 



M. de la Bastie's invention marks a distinct era in the history of 

 one of our most important industries. Never during the history of 

 glass-manufacture, which extends over some 3,500 years, has any radi- 

 cal change been effected in its character. The glass-blowers of Egypt, 

 who practised their art before the exodus of the children of Israel, 

 and representations of whom have been found on monuments as an- 

 cient as that event, produced a similar glass to that of our own times. 

 This has been proved by an examination of glass ornaments which 

 have been discovered in tombs as ancient as the days of Moses. It 

 has been proved, too, by a large bead of glass, found at Thebes, upon 

 which was inscribed the name of a monarch who lived 1,500 years 

 B. c, and which glass M^as of the same specific gravity as our own 

 crown-glass. It is true Pliny mentions that a combination was de- 

 vised in the reign of Tiberius, which produced a flexible glass ; but 

 both the inventor and apparatus were destroyed, in order, it is said, 

 to prevent the value of copper, silver, and gold, from becoming depre- 

 ciated. There is, however, no evidence whatever that this was the 

 toughening process of De la Bastie, nor does the record in any way 

 detract from the merits of that gentleman as the inventor of an im- 

 portant economic process. The fact remains that the world has now 

 given to it for the first time, in a practical form, an invention by which 

 the brittleness of glass is superseded by an attribute of the most 

 valuable nature toughness. It is by no means improbable that the 

 old adage, " as brittle as glass," will soon be superseded by a new one 

 " as tough as glass." 



What may be the ultimate result of the introduction of this inven- 

 tion in practice it is difl&cult to foresee, so wide-spread, so universal 

 does its application seem. Not only is it desirable to render durable 

 such articles as are at present made from glass, but to satisfy a want 

 long felt in every dej^artraent of art, science, and manufacture, of 

 such a material as toughened glass ; and this want can now be satis- 

 fied. So numerous are the opportunities which present for its applica- 

 tion, and so well adapted does it appear to be where cleanliness, trans- 

 parency, resistance to heat and chemical action, and comparative in- 



