202 THE OCEAN WORLD. 



It is, as we have said, only in the warm parts of the Indian and 

 Pacific Oceans that the great mass of these islands are found. They 

 give birth towards the south to the group of atolls known as the archi- 

 pelago of the Bashee Islands, the extreme limit of the region being 

 the Isle of Ducie. A multitude of other islands of the same nature are 

 sparsely scattered over the sea, up to the east coast of Australia. There 

 are enormous areas here, in which every single island is of coral forma- 

 tion, and is raised to the height at which the waves can throw up 

 fragments. The Radack group is a quadrilateral, 400 miles long by 

 240 broad. Between this group and the Low Archipelago itself, 840 

 miles by 420, there are groups and single islands covering a linear 

 space of more than 4,000 miles. To the north of the Equator, the 

 archipelago of the Caroline Islands constitutes a very considerable 

 group of coral islands, comprehending upwards of 1,000, extending in 

 a broad belt over nearly 40*^ of longitude. On the other hand, all 

 along the coast of the American continent, round the Galapagos and 

 the Isle of Paques, we find no trace of them. The reason assigned 

 is, that in these regions a great current of cold water, flowing from 

 the Antarctic Pole, so much lowers the temperature of the sea, that 

 the corals can no longer exist. 



We still meet with atolls in the Chinese Seas, and coral barrier 

 reefs are abundant round the Marianne and Philippine Islands. These 

 marginal reefs form also an immense tract, from the Isle of Timor, 

 along the south coast of Sumatra, up to the Island of Nicobar, in the 

 Bay of Bengal. 



To the west of the Indian Peninsula, the Maldive and Laccadive 

 Islands form the extremity of another group of atolls, and important 

 madreporic reefs, which extend towards the south, by the Maldives 

 and the Chagos Islands ; they consist of low coral formations, densely 

 clothed with cocoa-nut trees. The Maldives, the most southerly 

 cluster, include upwards of 1,000 islands and reefs ; the Laccadives, 

 seventeen in number, are of similar origin. The Saya de Malha 

 Bank, towards the south-east, constitutes a further group of madreporic 

 islets. Finally, the coast of the Mauritius, of Madagascar, of the 

 Seychelles, and even the African continent, from the northern extremity 

 of the Mozambique Channel to the bottom of the Red Sea, are 

 studded with numerous reefs of the same nature. They fail, however, 

 almost completely, along the coast of the Asiatic continent, where, 

 among others, the waters of the Euphrates, the Indus, and the Ganges, 

 enter the sea. The western coast of Africa, and the east coast of the 

 American continent, are almost entirely destitute of great madreporic 

 reefs, but they abound in the Caribbean Seas. In the Gulf of Mexico, 



