242 



Geology of the Xeilgherries. 



[No. 12, NEW SERIES. 



ing to the configuration of the adjoining altered garnets, also 

 occur. From these appearances, it would seem, that the garnets, 

 their surfaces being previously fused by heat, were submerged in 

 melted Quartz that had lost tne amount of caloric adequate for 

 their further fusion and was beginning to crystallize. In this 

 instance I apprehend the garnets were projected from below, 

 along with their matrix. In many cases however I am of opinion 

 that cavities in Quartz veins form natural alembics (like the geodes 

 in volcanic rocks enclosing zeolite minerals), in which electrical or 

 other powerful natural agents operate to produce garnets ; the 

 ingredients silica alumina, iron manganese, ice. being derived from 

 the adjoining rock. 



In proof of this latter surmise I may mention that I have garnets 

 in my possession containing small crystals of Quartz, which fell 

 from the sides of the cavities into the mineral while it was in a 



fluid state. 



Returning from the garnet valley, I found my way back to the 

 Cantonment over a route totally different, entering Ootacamund 

 by descending a hill immediately behind Dr. "Wight's house : this 

 eminence seen from the Cantonment has a conical appearance but 

 its real shape is the frustrum of a pyramid. 



Garnet Rock is its base, overlaid by iron which occurs under 

 the following conditions. 



[a.] Encrusting a rock probably # the same as the base of the 

 Hill, but now hastening into a crumbling sandstone from the 

 absence of the compact Felspar that cemented it. The surface of 

 this rock is cavernous, and possesses a decayed appearance. The 

 iron has followed the exact configuration of it, however and en- 

 tirely coated its exterior, manifesting that decay had commenced to 

 take place prior to its being invested by the iron. 



(b.) As iron mica diffused throughout the interior of the same 

 rock. 



(c.) In veins traversing the rock. 



(d.) In veins running down the side of the Hill, and embedded 



in the soil. 



