Besides these, there are several small satellite islands: Great Nicobar possesses Kondul and Kabra; Little Nicobar, Milo and Menchal, with Treis, Trak, and Meroë further off; and lastly, near the south extremity of Tilanchong, there is the rocky islet named "Isle of Man."[109] There are villages on Kondul and Milo, but Batti Malv and Tilanchong are uninhabited. Two large isolated coral banks occur--one near Chaura, with only 1-1/2 fathoms of water; and another, far more extensive, in the Sombrero Channel, with 11 fathoms of water above it. Although the Nicobar Islands are scarcely ever heard of, the China Mail boats and other great ocean steamers pass almost in sight of them nearly every day, and they possess in the central group one of the finest harbours in the eastern seas. Nankauri Harbour has not only entrances on the east and west, that make it practicable for any sort of vessel in both monsoons, but these are further protected by the islands of Trinkat and Kachal respectively, which give sheltered anchorage outside the mouth of the harbour itself. By any other nation than the British it would be highly valued at the present time as a coaling station, but, owing to its proximity to the Straits Settlements, and the failure of the small islands around to produce anything more valuable than coconuts, it is completely neglected by its possessors, from both commercial and strategical standpoints. The natives of the group number at present a few short of 6000 (to which should be added a possible 300-400 Shom Pe[.n]), and there are generally some 200 foreigners resident in the north during the trading monsoon. The islands increase in size as they are passed towards the south, but the contrary is the case with regard to population, which decreases regularly, island by island, with one or two exceptions, from Kar Nicobar in the north with 3451 inhabitants, to Great Nicobar with only 87.[110] * * * * * "The Nicobar Islands belong to an area of elevation which can be traced from the Bay of Bengal far into the southern seas,[111] and is characterised by two phenomena: first, the activity of the interior of the earth, showing itself in volcanic action; and secondly, the activity of the coralline animals, disclosing itself in the formation of that kind of coral reefs known as fringing or coast reefs. The islands occupy a gap without volcanoes between the volcanic ranges of Sumatra, and Barren and Narkondam Islands, and the occurrence of young volcanic rock in them is improbable. They are distinctly characterised as a portion of the chain of oceanic elevation which began in former geological periods and still continues, by the upheaved coral banks, and by the continuous formation of coral reefs. The synclinals and anticlinals in the geological structure of the islands are coincident with the direction of the great geological line of elevation which connects the northern part of Sumatra with the Andamans.