MODE XIV. SILICEOU3 GLUTENITE. 237 



with avidity, becoming greenish and translucent, 

 so as to resemble a felsite or jad. 1242. 



A sand-stone of a violet colour, common be- 

 tween Antibes and Frejus. It contains bits of 

 porphyry, and fragments of other sand-stones. 

 1462. 



Siliceous sand-stone, which resembles gneiss, 

 and alternates with lime-stone and slate. 763. 



Beds of a beautiful sand-stone, composed of 

 adherent grains of quartz. 1370. 



A green sand-stone, of little fragments of quartz, 

 in a cement of felsite. 1539. 



Sand is not only the produce of crystallisation, 

 but may even be produced artificially by an ope- 

 ration of that kind. 1375. 



In 1751, a mountain between Sallenche and 

 Servoz fell down, with such a thick and horrible 

 dust, diffused to the distance of five leagues, that 

 people thought the end of the world was arrived. 

 It was undermined by a lake ; and vast masses of 

 stone fell down day and night with a noise like 

 thunder. Among the ruins of this mountain Saus- 

 sure found the following singular sand-stone : 



" Fragments of a kind of greenish sand-stone, 

 externally spotted, very hard, and of a very fine 

 grain*. 



* The bricia of Rosenberg, which fell in 1806, somewhat re- 



