254 Some Account of the late M. Gm?ia7id. 



succeeded in soldering pieces of glass which have left no trace of 

 their separation : at first these pieces were only cemented ; there 

 was frequently even air or sand between the united surfaces ; in 

 these cases, he cut along the line of junction a small semi-cylin- 

 drical groove, in order that the vitreous matter, while melting, 

 might fill it, not by flowing from its edges to the bottom, but by 

 raising the bottom itself ; and, by repeating this operation a suf- 

 ficient number of times, he declares, that he has succeeded in 

 totally effacing all traces of junction. 



In 1798 or 1799, M. Guinard, having visited Paris, presented 

 to several men of science, and among others, to the late M. 

 de Lalande, several disks of from four to six inches, of the glass 

 which he obtained in sawing his blocks, (not having at this period 

 thought of the expedient of re-melting them ;) that celebrated 

 astronomer valued them highly, and having inquired of M. 

 Guinand what he intended to do with them, the latter expressed 

 his wish that they might be made into object-lenses, in order to 

 ascertain if the glass which he procured by means of his process 

 was of the kind that had been so long desired ; but M. de Lalande 

 having understood that he was conversant with optics, advised 

 him to work them up himself, so as to demonstrate the goodness 

 of his glass. M. Guinand followed this advice, and while con- 

 tinuing his manufacture of bells for repeaters, he pursued for se- 

 veral years the making of glass and the working of lenses ; he 

 constructed achromatic telescopes, some of which had object 

 glasses of four or five inches, perfectly free from striae, and 

 having purchased a small water-mill at Brenets (where he still 

 resides) he adapted it to the polishing of his glass. Notwith- 

 standing the advice of M. de Lalande, he made no effort to ob- 

 tain the prizes offered for his discovery, because, while he was 

 still not sufficiently convinced that his glass possessed all the 

 qualities required, (which cannot be positively ascertained until it 

 is wrought) the proposals of one of those societies, of which he 

 possessed a copy, requiring that the whole detail of the processes 

 by which it is obtained should be revealed to different committees, 

 before any decision is made, he was apprehensive that some dif- 



