336 



On the Later itic Formation. 



[Oct. 



grained granites and hornblende rocks on their decomposing edges. 

 The mere process of decomposition alone, it may be imagined, 

 not taking into consideration other agents, can be better studied in such 

 a country as India, where primitive formations abound, to the almost 

 total exclusion of others. In both Europe and America aqueous and 

 i;^;jc.'us a -tion are in operation, but in India, or rather in that portion 

 licw alluled to, no volcanoes are inactive existence, no inland seas or 

 lakes worthy of the name are depositing ; oxydation and decomposiiion 

 are in almost undisturbed possession, and rioting like the worm, slowly 

 but surely. To one who has visited both the new and old world the 

 contrast afforded is very striking ; the one abounding in rivers and lakes 

 of vast extent, the land emerging as it were gradually from the giant 

 embrace of the deep, fresh and blooming and prolific ; the other, of 

 which India is a part, having scarcely any fluid on its surface, dry, parch- 

 ed, wrinkled, and " blasted vvith antiquity." India even now just looks 

 as if it had never risen from under the curse attached to all creation on 

 the fall of man, lying prostrate and stricken, and the decomposition that 

 is going on, is only in accordance with that same curse which consigned 

 all things to decay. 



It is now time to enquire what are the circumstances which give 

 tendency to decomposition. The grand fundamental rock in 

 India, and perhaps over the greater part of the old continent, is a 

 granite containing hornblende ; but besides this sienitic granite, horn- 

 blende rock, or primitive trap, is found constantly associated with it, 

 and these two occupy immense tracts, to the exclusion often of other 

 rocks. The peculiarity of hornblende is the quantity of iron entering 

 into its composition ; this is so great in some ]5ai'ts of India that Dr. 

 Heyne remarks he would be disposed to call it ferrulite. The iron in the 

 hornblende attracts oxygen,and the rock is loosened, and decomposes easily. 

 This tendency to decomposition in sienitic granite compared with simple 

 granite, was long since remarked by Heyne, in his Statistical Sketches' 

 The ferruginous character of hornblende is therefore established, and it is 

 to the decomposition of rocks containing much hornblende that Dr. Benza 

 refers the formation of lithomargic earth. This talented observer, whose 

 writings have tended to diffuse a taste through the Presidency for 

 geological studies, and to whose researches we all owe so much, has been 

 puzzled to account for the decomposition of rocks containing hornblende 

 into lithomarge on the Neilgherry Hills (he might have added Coorg and 

 the Western Coast), and not in other localities in India, where such rocks 

 abound. In even hinting at an explanation, he is doubtful whether to 

 refer it to the present agency of cold, frost, &c. &c. which are in constant 

 operation on those hills, or to actions long since past. In the l2th Num- 



