Some Account of the late M. Guinand. 249 



with materials procured from abroad ; at another time it was not 

 until after having employed several days, and consumed much 

 wood in heating it, that he noticed an essential defect in its con- 

 struction, whicli obliged him to suspend the melting ; sometimes 

 his crucibles, which he had procured at great expense, or manu- 

 factured himself, cracked without his being able to discover the 

 cause, and the vitreous matter escaped among the ashes, and was 

 lost. After each of these trials he was obliged to employ a 

 longer or a shorter interval in earning the means of subsistence, 

 and of purchasing wood, and the necessary materials for his fur- 

 nace, his crucibles, and his glass. These fruitless attempts dis- 

 couraged him on some occasions, but on others excited him so as 

 to deprive him of rest, and he meditated day and night on the 

 probable causes of the accidents, and on the means of obviating 

 them. At length, however, he obtained a block (^culot) of glass, 

 of about two hundred weight ; having sawed this block vertically, 

 he polished one of the sections, in order to examine what had 

 taken place during fusion, and the following were the appear- 

 ances : — On the upper surface of the vitreous matter there were 

 many little semi-globules, which had the appearance of drops of 

 water, terminating by a thread or little tube of greater or less 

 depth, at the extremity of which there was a small spherical bulb. 

 The cause of this appearance was, that these drops and tubes 

 consisted of a denser kind of -glass than the rest of the block* 

 In another part there arose from the bottom of the crucible other 

 cylinders, or tubes, terminating also in a kind of swelling or 

 bulb ; these had a hollow appearance, because they were formed 

 of a substance less dense than the rest of the glass ; and lastly, 

 here and there were seen specks, or grains, ending with a tail 

 or train of a substance also less dense than the rest of the mass 

 in which they floated ; these, on account of their appearance, he 

 denominated comets. In evidence of this result we still possess 

 a specimen of the glass which M. Guinand formerly sent to us. 

 The block here spoken of has long ago disappeared. 



The following is M. Guinand's explanation of these effects :— 

 Having often seen on the surface of his glass small globules, of 



