MODE XIV. CALCAREOUS GLUTENITE. 535 



Bonhomme, Saussure observed a remarkable sand- 

 stone, which he thus describes : 



" All the beds of sandstone observed on this Of Fours, 

 mountain do not contain rolled pebbles; there 

 being irregular alternations of beds of pure sand- 

 stone, and beds mixed with pebbles. The most 

 elevated contain none. The highest of those 

 which contain any, is a continued bed of a foot in 

 thickness, and which rises 30 degrees to the 

 N. W. 



" Some of these beds, filled with pebbles, pre- 

 sent a very remarkable singularity : on their ex- 

 ternal surface exposed to the air, is observed a 

 kind of network formed of black and saliant veins, 

 two or three inches above the surfa.ce of the rock ; 

 the meshes of this net are sometimes irregular; 

 but for the most part they are oblique-angled 

 quadrilaterals, whose sides are eight or ten inches 

 long. As these rocks have all a tendency to split 

 in rhomboids, it seems that there have been for- 

 merly clefts, which divided the beds in parts of 

 this form ; and that these clefts have been filled 

 by sand, which has been cemented by a fer- 

 ruginous juice : this solid gluten, has made these 

 parts harder than the rest of the rock; and when 

 the injuries of the air have attacked the surface of 

 these beds, the meshes of the net have remained 

 protuberant. 



