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Dr. Rink, (Geologist attached to the Danish Expedition,) on 

 the Geological Structure of the Nicobars, in a letter to Dr. 

 M'Clelland. 



My dear Sir, — Leaving Calcutta, I expected to follow the 

 Corvet " Galathea" on her circumnavigation; but several circum- 

 stances induced me to alter my plan, and to remain here at the 

 temporary Danish establishment at the Nicobar Islands, and thus, at 

 all events, await the resolution of our government as to their retain- 

 ing the possession of the Islands or not. What especially induced 

 me to this, was that they contain a large field for every branch of 

 natural science and investigation, more particularly so in my depart- 

 ment, where they oifered many points which seemed worthy of more 

 accurate observation and reflection, than it was possible to bestow 

 during a few excursions while the Corvet Galathea remained, parti- 

 cularly as the country is wild and impenetrable, and the season 

 happened to be hot. But still I have so much hope, that it might 

 be of some interest to you, that I avail myself of the opportunity 

 offered me by Captain Lewis, who leaves this harbour for India, to 

 send you some general observations concerning the constitution of 

 these Islands, being so closely connected with those countries, whose 

 Geology occupies your attention and owes so very much to you. 



The hills of the northern group, Nicobar Islands, are surrounded 

 by a low belt of coral formation, particularly the Islands Teressa, 

 Bampuka, Tillangschong, Nangkoory, Kamorta, Trinket. Those 

 I have had opportunity of visiting, form a system quite different from 

 the southern group. These Islands are all for the greatest part of 

 Plutonic origin. The rocks belong to those, which at remote periods 

 have broken through, and disrupted granite, particularly serpentinic. 

 All the places presenting a section of the soil, shewed compact 

 varieties of serpentine or serpentinic gabro ; but many pebbles found 

 on the coasts and in the beds of the rivulets present specimens 

 of a more crystalline aspect, containing the ingredients separated 

 from each other ; arid according to this there is no doubt, that 

 different kinds of sienitic, augitic, and dioritic porphyry alternate 

 with the principal serpentinic rocks. The small Islands, Bampuka and 

 Tillangschong, consist of these merely Plutonic rocks, rising out of 



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