Close to Cape Negrais terminate the Arakan Hills, one of a series of ranges that run down from the Eastern Himalayas; and just south of Acheen Head we have the Gunong Mas, Batu Mukuruh, and other mountains; therefore, looking at a map of the district, it seems difficult to avoid the conclusion that the whole of the islands last enumerated are nothing less than a continuation southward of the Arakan Hills. But although they form a chain that seems to indicate a past union of Sumatra and Burma, investigation proves that this is far from being the case. For soundings in this part of the ocean show that between the Nicobars and the group of islands adjacent to the north-east point of Sumatra--entering from the open sea to the west, and thence trending north between the Andamans and Malay Peninsula almost as far as the latitude of Narkondam--there runs a long tongue of depressed ocean bed with depths everywhere over 1000 fathoms. This fact, together with the shallowness of the sea-bottom around and connecting the Andamans with the Arakan Yoma Peninsula, suggests the inference that the former were at one time past the termination of a seaward extension from Cape Negrais of the Arakan Yoma Range--a conclusion that is in some degree emphasized by the zoological and botanical conditions common to the two. The principal islands are, Great and Little Andaman, Rutland and the Labyrinths, the Archipelago, North Sentinel, Interview Island, Landfall Island, and the Cocos, but there are many smaller adjacent, while to the eastward are the off-lying volcanic islets of Narkondam and Barren Island. The total area of the group is 2508 square miles.[84] Great Andaman--in which may be included Landfall and Rutland Islands, for the whole land mass is so compact and divided up by such narrow shallow straits that it appears to be one single island that has been broken up by subsidence and adjoining volcanic action--is 142 miles long, and 17 miles broad at its widest point. There are generally stated to be two straits, but as one of them bifurcates, the Great Andaman proper is really cut into four parts. Austin Strait, which divides North from Middle Andaman, is very narrow and intricate, and not to be traversed by boats at low tide; but the Andaman Strait,--generally 2 to 3 cables wide--which separates South from Middle Andaman at a spot where the hills are lower than elsewhere, although intricate, and possessing a bar at its eastern mouth with a depth of 9 or 10 feet at low water, has depths from 10 to 14 fathoms throughout the narrower part, and nowhere less than 3 fathoms at low water. The stream is never strong, and the R.I.M.S. _Investigator_ passed through three times while surveying the islands in 1888.