Dec. 1861.] Geology of the Neilgherries. 253 



Garnet rock and compact red granite again occur near Coonoor ; 

 indeed I conjecture that the former rock extends down the Ghauts 

 as far as Cape Comorin, for I observed some years ago that a part 

 of the beach, at that Cape, consisted of very minute garnets aris- 

 ing probably from the disintegration of garnet rock. 



Between Coonoor and a ridge emanating from Dodabett, six 

 miles to the north of that place, the conglomerate which I observ- 

 ed accompanying the garnet conglomerate in the garnet valley, is 

 distributed over the face of the country along with red iron ore, 

 and a highly ferraginous conglomerate. The ridge itself is com- 

 posed of syenite ; garnet rock, and eurite, (quartz and felspar.) 



Since this paper was first written Dr. Burrell found galena and 

 sulphuret of copper, near Ootakamund, and I discovered silicate of 

 zinc in the same locality. 



H. C. 



An outline of the Geological History of the Neilgherry Hills. By 

 Major H. Congbeve. 



In the molluscs and zoophytes of the Cambrian system, and the 

 corals, crinoidea, Crustacea, conchifera, and the eoprolites or fossil 

 excrement of fishes in the silurian ; the two great divisions of the 

 grauwacke formation ; the clearest testimony is afforded, that a 

 vast ocean rolled its waters over the metamorphic rocks immedi- 

 ately beneath this group. The rocks of the metamorphic series, 

 gneiss and hornblende schist chiefly, formed the bottom of this 

 ocean they having been originally granite and syenite, subsequent- 

 ly metamorphosed by pressure and the mechanical and dynamical 

 action of molten-trap rapidly and continuously over them. 



The metamorphic rocks have been found in all quarters of the 

 globe, and appear as surface rocks in most countries ; but this is 

 not the case with the grauwacke group. And this can only be 

 accounted for by conceiving that, in places where rocks of this 

 series are wanting, the waters of the grauwacke ocean were so tur- 

 bulent and disturbed as not to admit of any deposit ; the materials 



