44 



CONTRIBUTIONS TO THE ORNITHOLOGY OF INDIA. 



" The third class consists of coral formations, belonging to the 

 most recent or the present period. Coral banks of great thickness 

 are found on Car Nicobar, Bompoka and several other islands ; 

 they consist partly of a compact coral limestone, partly of a coral or 

 shell conglomerate upheaved up to 30 and 40 feet above the present 

 level of the sea ; on all the islands, the original area is to be 

 observed enlarged by coral-land, which is only separated by the 

 higher sand dunes along the shore, from the still continuing forma- 

 tion of the coral-reefs surrounding all the islands in the character of 

 fringing-reefs Although these raised coral banks are a decided 

 evidence in favor of the long-continued upheaval of the islands — ■ 

 that in connection with the eruption of the serpentines and gabbros 

 — the formation of the flat coral land elevated only a few feet 

 above the level of the sea can, on the other hand, be explained 

 by the accumulation of coral fragments, of sand and shells by the 

 waves and breakers on the shallow surface of the fringing-reefs. 



" Vegetation in its original state always indicates the character 

 of the soil, provided the atmospheric conditions are the same. 

 This is remarkably true in this case of the Nicobars. Neither the 

 difference in the latitude from the most northern to the most 

 southern islands {2\ degrees), nor the difference ,of the absolute 

 elevation (the highest hills on Great Nicobar only attain about 

 2,000 feet above the sea), is large enough to produce on the single 

 island, or parts of them, such a difference in the climatal condi- 

 tions, that on it alone an altered character of vegetation should 

 depend. Eocks, soil and vegetation are, therefore, on the Nicobars 

 in such a degree related to each other, that the areas marked on a 

 map as indicating various rocks would almost coincide with those 

 indicating the varieties of vegetation. 



" The results of these observations may be seen in the following 

 tabular view : — 



Geological character of the 

 underlying rock. 



Character of soil. 



Respective cha- 

 racter of vege- 

 tation. 



1. — Salt and brackish swamp, 

 damp marine alluvium. 



2. — Coral conglomerate and coral 

 sand, dry marine alluvium. 



3. — Coral conglomerate and coral 

 sand, beside dry fresh- water 

 alluvium. 



4. — Fresh- water swamp and damp 

 fresh-water alluvium. 



5. — Plastic clay, magnesian clay, 

 marls, and partially serpen- 

 tine. 



6. — Sandstone, slate, gabbro, dry 

 river alluvium. 



Swampy ground not capable of 



cultivation. 

 Fertile calcareous soil ; principal 



constituents, carbonate and 



phosphate of lime. 

 Fertile calcareous sandy soil. 



Swampy ground, capable of being 

 cultivated. 



Not fertile, clayey soil, principal 

 constituents, silicate of alu- 

 mina and silicate of magnesia. 



Loose clayey sandy soil, rich in 

 alkalies and lime, very fertile. 



Mangrove-forest. 



Cocoa-palm for- 

 est. 



Large forest trees. 



Pandanus forest. 

 Grassy plains. 



Jungle (the true 

 primeval forest). 



