256 Some Account of the late M. Gui7iand. 



Among the opticians who have used his glass, and whose 

 judgment cannot be questioned, may be particularly mentioned 

 M. Lerebours, an artist attached to the Board of Longitude at 

 Paris, who, during a visit to Brenets in 1820, having obtained 

 all the glass which M. Guinand then had in his possession, 

 though at that time it was not so perfect as he hoped to make it 

 by successive re-softenings, was so well satisfied with it that he 

 not only requested a fresh supply, but was induced to make over- 

 tures for obtaining a communication of the process. We may 

 also adduce M. Cauchoix*, who, in a notice relative to the teles- 

 copes placed in the last exhibition at the Louvre, has spoken o^ 

 the flint-glass, of which they are constructed, in a manner which 

 at once shews the goodness of M. Guinand's glass, and the good 

 faith of the French artist. When the Bibliotheque Uriverselle an- 

 nounced the formation of the Astronomical Society of London, 

 M. Guinand was requested (in 1821) to present to them a sample 

 of his glass, upon which they were pleased to make a report as 

 favourable as the small size of the specimen could warrant ; they 

 also very graciously offered another, on disks of a larger dimen- 

 sion. M. Guinand accepted the offer, and they have 

 progress a disk of seven inches, similar to those which have been 



the Brenets for two years in a state of inaction ill suited to the activity of hig 

 genuis. Confident that by new experiments he could raise his discovery to a 

 higher degree of improvement, he wrote to Bavaria, requesting that on re- 

 linquishing his pension he might be released from the engagements which he 

 contracted. His request having been granted, he ardently resumed his la- 

 bours, and it was during this last period of his life (a space of nearly seven 

 years)j that this ingenious and persevering artist succeeded in making those 

 disks of eleven and twelve inches English measure, which are wholly free 

 from defects, and which excite the astonishment and admiration of all who 

 are acquainted with the difficulty of procuring disks of flint-glass of even five 

 inches in diameter, fit for optical purposes. 



* Some time after M. Lerebours's visit to Switzerland, M. Cauchoix having 

 been accidentally informed that M. Guinand was the person who made this 

 excellent flint-glass, without a moment's delay posted to Brenets, a distance 

 of 300 miles, and not only purchased all the glass which was actually manu- 

 factured, but ordered those disks of extraordinary dimensions which we have 

 just noticed. 



