GEOLOGY OF CENTRAL INDIA. 



33 



sandstone slates of the north of Malwa. The latter is universally asso- 

 ciated with a breccia, contains iron ore in large quantities, and some- 

 times assumes the appearance of a nearly pure or ferruginous quartz 

 rock. Mr. Phillips, in describing primitive sandstone, which he classes 

 with the " inferior rocks," says (p. 158, Outlines of Geology,) that "de- 

 tached fragments of gneiss and clay slate occur in it," the clay slates are 

 classed with the " submedial rocks." In this case, however, the clay slates 

 must be of more ancient formation than the primitive sandstones, on which 

 they are found imbedded — Another strong objection to his classification. 



Micaceous, Talcose and Chloritic Schists. — These require no 

 definition — they are found passing into, and alternating with each other, 

 and into other rocks. 



Argillaceous Schist. — This name, adopted by Dr. Macculloch, 

 from the French, appears to me apt and comprehensive, and by it I 

 mean to indicate all those rocks which are usually included under the 

 heads " clay slate" and " grey wacke slate." Many of the argillaceous 

 schists of this district approach to the nature of grey wacke slate, as 

 commonly described. The transition from the one to the other, however, 

 is so gradual, that the more I have seen of these rocks, the more I have 

 been convinced that one general name ought to be applied to the 

 whole. The nature of each variety of argillaceous schist will, of course, 

 be described, and different adjuncts derived from their external charac- 

 ters, &c., made use of; such as — micaceous, talcose, chloritic, siliceo, 

 argillaceous, wackaceous, friable, sectile, &c., and when they approach to, 

 or pass into, any particular rock, this also will be mentioned. 



Hornblende Rocks. — This will include hornblende rock and horn- 

 blende slate. Some of the varieties of hornblende rock might be 



K 



