$din^ Acdount of the Idte M. Guinand, ' 251 



Here in particular that M. Guinand had great obstacles to sur- 

 ttiouiit ; so that, said he, the sacrifices and Exertions which he 

 had previously made, were trifling compared with those which he 

 afterwards underwent for the purpo^ of removing these va- 

 rious defects, and of rendering his glass homogeneous. 



Here we would gladly relate the numerous experiments by 

 which M. Guinand at length accomplished his grand discovery ; 

 but, as it still serves to procure for him some compensation for 

 his labours, we should be unworthy of the confidence he has re- 

 posed in ns were we to enter into any detail on this subject. We 

 shall therefore only state, that after many expensive trials, 

 M. Guinand having been so fortunate as to obtain glass of which 

 some parts \Vere perfectly homogeneous, and therefore destitute 

 bf thosB strife or threads from which flint-glass is so rarely found 

 free, he reflected on the different circumstances which, in this 

 experiment, might have contributed to so happy a result, so that 

 ift subsequent attempts he obtained blocks of gUss possessing 

 larger portions of homogeneous substance, and at length he has 

 almost arrived at a certainty of obtaining in the fusion of from 

 i^o to four hundred weight of glass, at least on^ half of that 

 substance perfectly homogeneous, and consequently fit for optical 

 purposes. 



Unable to make any further progress, he admits that his pro- 

 cesses have not yet attained all the perfection which might per- 

 haps be desired ; but, as he has by these means succeeded in 

 making disks, perfectly homogeneous, of tvelve, and in one in- 

 stance even of eighteen, inches in diameter*; and having no 



* Wliile occupied in his laboratory, M. GuinaDcl never permitted any per- 

 sons to be present, except his wife and son, who assisted him. On these oc- 

 casions they were generally secluded for many days and nights from society j 

 but when M. Guinand had nearly completed his operations, and had arrived at 

 a favourable result, his friends and neighbours were admitted, and partook of 

 some refreshment, while offering their congratulations on the termination of 

 his confinement. 



A year or two before his deatli, M. Guinand tried an experiment on a larger 

 scale than he had previously attempted. After much trouble and exertion he 

 succeeded in obtaining a disk of eighteen inches in diameter, of perfectly ho- 



