The first or northern division includes Bangao, Sangasanga, Tawi-tawi, Tandu-batu, and a large number of smaller islands, all of which are rough, volcanic, mountainous, and very sparsely populated. The second or southern division is a series of low, flat islands which are smaller in area but more thickly populated than those of the northern division. The principal names, beginning at the east, are the following: Kinapusan, Bintulan, Tabawan, South Ubian, Tandubas, Sikubun, Lata'an, Mantabwan, Banaran, Bilatan, Manuk-manka, and Simunul. Extensive reefs and narrow channels and shoals separate these islands from one another and from those of the northern division, rendering navigation between them impossible except in vessels of very light draft. Bangao, Sanga-sanga, and Tawi-tawi are separated by very narrow channels and are practically one island. Bangao forms the southwest extremity and is substantially one solid rock which rises perpendicularly to a height of 228 meters. It is a conspicuous landmark to vessels going through the Sibutu Passage. The town of Bangao is a military station and an open port; it has an excellent landlocked harbor and a very poor water supply. The town has been occupied by troops since 1882, but it has never attained any size or importance. Tawi-tawi Island is a continuous range of hills covered by thick and rich forests. The highest points in the range are the Dromedary peaks (591 meters) lying about the center of the island. The length of the island is about 34 miles and its greatest width 14 miles. It is next in size to the Island of Sulu, but it is very sparsely populated. Its chief settlements are Tungpatung, Balimbang, Lissum, and Bu'an on the south coast, and Tawi-tawi, Tata'an, Butung, Tumhubung, Tumbaga'an, Languyan, and Bas on the north. At Balimbang are built the best types of Sulu and Samal boats. Good timber abounds in the neighboring hills, and the little bay is transformed into a shipyard. The town used to be a famous rendezvous for Samal pirates. Tata'an had formerly a Spanish garrison; the present Moro town is a little distance to the south of the ruins of the fort and is called Butung. It is built on the hillside and commands a pretty view of the sea. It lies 100 miles east of Lahat Datu, East Borneo. The anchorage is deep and safe, being well protected by a large semicircle of reefs. A boa 30 feet long was killed on the island in 1903. Rubber and gutta-percha are found on this island. Tapioca and ubi are the staple products.