I OF FLINT. 



199 



It was likewise intersected by reddish lines, crossing each 

 other; in different directions, as in the ludus Helmontii. 



The doubts arising from this comparative examination in- Attempts to 

 duced me to inquire, whether it might not be the work of art, imitate it by 

 at least how near art could approach it, 



I have already noticed the facility with which silex is al- 

 tered by fire ; we could not think therefore of employing the 

 processes by which porcelain is covered. But might not the 

 same end be obtained, by cementations with a moderate 

 heat, long digestion, saline fusion, or combined solutions, 

 to set at work powerful affinities ? Chemical experiments 

 alone could throw light on this subject, and to them I had 

 recourse. 



It will be sufficient to give a brief account of the results 

 of the first unsuccessful attempts. 



Flint cemented in lime from marble, sulphate of lime, Unsuccessful 

 sulphate of alumine, and muriate of soda, underwent no tnals ' 

 alteration, as long as the heat was not carried to a certain 

 point. Beyond that it began to lose its colour, transparency, 

 and tenacity. 



A fragment of flint treated with caustic potash in a pla- 

 tina crucible experienced only a trifling diminution of 

 weight, more or less in proportion to the time in which it was 

 continued in a heat sufficient to keep the potash in fusion. 



Alumine being one of the constituent parts of calcedony, Alumine with 

 though in a small proportion, I conceived, that by treating exce3S of P ot ~ 

 the flint with a solution of potash saturated with alumine, 

 and adding a portion of free potash to act on the silex, the 

 affinity these two earths have been shown to possess for each 

 other*, and with a common solvent, must effect on the sur- 

 face of the silex a new combination, at a temperature inca- 

 pable of altering its nature. 



Considering on the other hand, that analysis had developed and the same 



in some calcedonies the presence of lime, I put a small with the addi " 



. . , . c a . . . . , tion ot lime, 



quantity with another piece ot flint into a similar preparation gaV e flint a si- 



of potash and alumine. ™ilar coat, 



These two experiments were made in platina crucibles, 



and the success exceeded my expectations, though they were 



* See our Journal, Vol. IV. p. 1G, 



not 



