MODE XIV. SILICEOUS GLUTENITE. 



Even the Egyptian kollanite above mentioned 

 might, without the balls of jasper and agate, be 

 considered as a large-grained sand-stone, singu- 

 larly formed of unctuous quartz. The large- 

 grained siliceous sand-stones are however far more 

 rare than those of a finer construction. It is not 

 unusual to find in them, as in other sand-stones, 

 nodules or veins of green earth or chlorite, a sub- 

 stance also common in sand ; and, like its parent 

 iron, more widely diffused than is commonly ima- 

 gined. 



Mr. Kirwan's account of siliceous sand-stone is 

 too interesting to be omitted. 



" This stone is generally reckoned among the 

 secondary; yet where no organic remains are found 

 in it, where it does not rest on any secondary 

 stone, where no secondary stone enters in its com- 

 position, I do not see why it may not be aggre- 

 gated to the primary. Sand, amongst the con- 

 vulsions occasioned by the volcanic eruptions 

 before the creation of animals, must have been 

 formed; and even independently of these, some 

 must have been deposited, during or after the 

 crystallisation of the various substances contained 

 in the elastic fluid. See 5th Sauss. 294. Mount 

 Jorat and the Coteau de Boissy, near Geneva, 

 1 Sauss. 246. 349, seem to be primeval ; so also 

 the sand-stone found in the island of Bornholm, 



