556 



THE POPULAR SCIENCE MONTHLY. 



Tvas foiled in every attempt to regain it. There was the hard fact 

 staring him in the face, that he had succeeded in depriving glass of 

 its brittleness, as shown by specimens around him ; but there was the 

 harder fact before him, that he had lost the key of his success. Never- 

 theless he labored on, and at the end of the period above mentioned 

 he had the satisfaction of finding all his anxieties at an end ; his toils 

 were requited by the rediscovery of his secret. He has since worked 

 at it most assiduoiisly, and has now brought it into jDractical working 

 order, rendering the process as certain of success as any in use in the 

 arts and manufactures in the present day. 



As already observed, M. de la Bastie is not a glass-manufacturer ; 

 he therefore had to reheat glass articles when toughening them. It, 

 however, by no means follows that the toughening process cannot be 

 applied in the course of manufacture, thus avoiding reheating. On 

 the contrary, it not only can be, but has been, applied at glass-works 

 to glass just made, and so saves the costly and time-absorbing process 

 of annealing. But, for reasons stated, M. de la Bastie had to apply 

 the process to the manufactured article; and the method adopted, and 

 the apparatus used in its application, next merit attention. In the 

 first place, the glass to be toughened had to be raised to a very high 



Fig. 1. 



temperature the higher the temperature the better the risk of break- 

 ing the glass being thereby reduced, and the shrinkage or condensa- 

 tion being increased. It was therefore advantageous, and often neces- 

 sary, to heat the glass to the point of softening; but in that condition 

 glass articles readily lost their shape, and had to be plunged into the 



