340 Report on the ponderous Mint Glass intended 



M. Lebaude, on this occasion, merely produce! specimens 

 of ponderous glass, and which could not satisfy the wants 

 of opticians: the Academy was therefore obliged, in 17S6, 

 to renew the same subject as a prize dissertation, and the 

 sum offered was 12000 -ivres. In announcing the subject 

 proposed, a process was required, by means of which the 

 quantity of ponderous glass necessary to supply the wants 

 of commerce might be constantly supplied, and without the 

 defects of flint glass. 



Since the above period, essays have certainly been pre- 

 sented, but they were either too imperfect or too meagre for 

 attaining the essential object which government had in view > 

 namely, that of furnishing France vyith all the ponderous 

 glass requisite for optical instruments, without having re- 

 course to foreigners. This enterprise was not unattended 

 with difficulties in its execution, -because the heads of 

 great glass-works, who alone could enter into these delicate 

 and difficult inquiries with any chance of success, could not 

 flatter themselves that the sale to opticians, of ponderous glass 

 blown without any defects, was likely to reimburse them for 

 the enormous expense this degree of perfection requires. 

 This consideration is sufficient to show, that we cannot as- 

 similate simple essays with works which should serve to 

 vivify and extend an important branch of industry and 

 commerce. 



M. Doufourgerais, manufacturer of glass to the emperor, 

 already known by the celebrity of his manufactory of cry- 

 stal glass at Mont Cenis, has certainly excited a lively in- 

 terest among us, on account of the decided preference which 

 the produce of his industry has generally obtained over the 

 glass of England and Bohemia, although he had to surmount 

 many powerful obstacles. The Institute could not view 

 without extreme satisfaction the works on a great scale which 

 this ingenious and zealous manufacturer has recently exe- 

 cuted. One specimen consists of 600 kilogrammes of a glass 

 weightier than flint glass. It is 9000 millimetres thick, and 

 L70 centimetres high. He has already sold upwards of 300 

 kilogrammes of it to opticians, and the remainder will soon 

 be bought up also, without the price being adequate to the 



capital 



