344 On a sculptured Head In Flint, 



approached a little more to a glazed enamel, and had a 

 pretty lively lustre ; hut this mineral, also completely dif- 

 ferent from common flint, was only an opake white chalce- 

 dony upon a more hyaline chalcedony. It was moreover in- 

 tersected by reddish-coloured lines, which crossed in dif- 

 ferent ways, in the manner of the ludus. ■ 



The doubts excited in my minJ by these comparisons 

 engaged me to examine if the subject of investigation could 

 not have been the work of art, or at least how nearly it ap- 

 proached it. 



I have already remarked how easily silex is altered by the 

 fire ; it is not necessary, therefore, to have recourse to the 

 processes of coating porcelain to solve our difficulties. But 

 might not the same end be attained by cementations at a 

 moderate heat, long digestions in saline fusions, or in com- 

 bined solutions, in order to bring into play efficacious affi- 

 nities? — Chemical experiments can alone throw light on 

 the subject. 



It will be sufficient cursorily to explain the results of the 

 first fruitless trials. 



Silex, cemented in the lime of marble, sulphate of lime, 

 sulphate of alumine, and iu the muriate of soda, experienced 

 no alteration so long as the heat was not pushed beyond a 

 certain degree, after passing which it begins to lose its co- 

 lour, transparency, and tenacity. 



A fragment of silex, treated in caustic potash in a platina 

 crucible, only experienced a slight diminution of weight, 

 more or less considerable according to the time that it was 

 kept in a heat capable of maintaining the potash in fusion. 



Alumine being (although in a small proportion) one of 

 the constituent parts of chalcedony, I thought that by treat- 

 ing silex in a solution of potash saturated with alumine, and 

 adding to it a quantity of free potash to act upon the silex, 

 the well-known affinity of the two earths for each other, 

 and with a common solvent, would operate a new combina- 

 tion on the surface of the silex, at a degree of heat incapable 

 of causing any other alteration. 



Considering, on the other hand, that an analysis had 

 ascertained the presence of lime in some chalcedonies, I 



put 



