412 Notes, principally Geological, [No. 162. 



and no country in the world, perhaps, affords better opportunities for 

 their study than S. India. Some of the fissures of the dyke on the 

 ridge of the hill are filled with calc spar, and many of the loose blocks 

 encrusted with the same mineral and compact reddish kunker. 

 Thin seams of nephrite occasionally intervene between the basalt and 

 its walls; and the limestone associated with the slates has in some 

 instances been converted into chert after assimilating calcedony in tex- 

 ture and colour. 



Where basaltic greenstone and granite,, or other plutonic rocks have 

 extended on a great scale, we generally find not only a great tendency 

 to crystalline and mineral development, but a segregation of the ordi- 

 nary components of the rocks of the heated area, of such magnitude as 

 to be at once apparent in the physical aspect of the country in large 

 beds and ridges of quartz, iron ore, or quartz strongly impregnated 

 with iron, felspathic clays, &c. 



But to return. At the Southern base of the ridge the shales acquire 

 a massive structure, and form a soft lilac tinted rock speckled with 

 green, with a slightly soapy feel and easily sectile, which melts before 

 the blow- pipe per se into a pearly glass. It is here quarried and carved 

 into images, figures of deities, &c, which are exported. 



I had a very neat representation of the Avatars of Vishnu, executed 

 on a large slab of this material which, though I have given it the 

 name of figure-stone, by no means resembles the agalmatolite of China, 

 used for similar purposes.* Much of the water rising through the 

 fissures of the rock around the base of the ridge is impregnated with 

 muriate of soda ; and further West to Ganlapaud the plain is inter- 

 sected with trap dykes penetrating the grey limestone and its asso- 

 ciated shales, which are often greatly altered and silicified. The 

 general direction of the strata observed was E. S. E. and S. E. and dip 

 N. of E. Hence, the plain to the base of the Rayelcherroo hills is 

 chiefly limestone and associated shales and schists covered with regur. 

 South of I^yelcherroo the limestone becomes of a waxy texture, 

 compact, of a conchoidal fracture, veined and dotted with delicate 

 shades of green, yellow, red, and imbeds pyrites. It rises into irregu- 

 lar hills and ridges, alternates with sandstone, and sandstone conglo- 

 merate. The hills become still more confused and jumbled, as the 



* The Agalmatolite is wholly infusible. This is probably one of the many varieties 

 of steatite.— Eds. 



