1845.] Diluvial and Wave Translation Theories. 225 



in language free, as far as possible, from scientific terms, will serve 

 more effectually towards the carrying out General Briggs's views. 

 Existence of erratic Blocks and Boulders in Southern India. 



It was Brongniart, I believe, on the authority of M. de la Luc, who 

 first spread among the Savans of Europe the idea that the rounded 

 blocks of granite around and in the vicinity of Hydrabad in the plains 

 of the Deccan were true erratic boulders ; but after a close and ex- 

 tended examination of them, and of the rocks for many miles around, 

 I am convinced that these blocks are in situ (in place,) or nearly so, 

 since they invariably rest upon, or near a granite of the same petro- 

 graphical character ; and that they owe their prevailing globular and 

 rounded form to a process of spontaneous concentric exfoliation which 

 I have endeavoured to explain in a paper published in the Journal 

 of the Royal Asiatic Society for 1840. 



The granite and limestone blocks at Puttuncherroo near Hydrabad, 

 around Bangalore, Bellary, and in the Carnatic, wherever examined 

 closely, I have found to be of precisely similar origin. 



The formation in all these localities is one of granitic rocks, gneiss, 

 and other contemporaneous crystalline schists, penetrated by dykes of 

 basaltic greenstone, varying in structure from compact basalt to crys- 

 talline and porphyritic greenstone. The disposition of the last rock 

 to assume a globular or spheroidal shape in weathering is still more 

 remarkable than in the granite, which is often seen in rhomboidal and 

 cuboidal masses, the angles of which are first blunted, and then round- 

 ed off by the exfoliation. 



The Hydrabad granite blocks are seen lying singly, in confusedly 

 piled heaps, or resting as tors or logging stones on bare bosses of a 

 similar granite ; and sometimes buried or half-buried in a soil formed 

 by their own weathering. 



At Lunjabunda, in the Kurnool district, I observed a single globular 

 mass of granite about 18 feet in circumference, resting on a bare boss 

 of the same rock, from which apparently the slightest touch would 

 send it rolling to a considerable distance in the plain, and of which 

 the subjoined diagram may serve to convey some idea. ( See plate, 

 Diagram, No. I.J 



The globular block A, is cemented to the boss beneath it B, by a 

 paste a, arising from the decomposition of the granite itself, a felspathic 



