Besides the volcanoes we have already described, there are many others situated in mid-ocean far from any continent. A brief description will be given of a few of these.

All the three great central oceans, the Pacific, the Atlantic, and the Indian, contain numerous volcanic islands, some of which rise many thousands of feet above the general level.

We will begin with a description of some of the more important volcanic islands of the Pacific. It was first pointed out by Kotzebue, and afterwards by Darwin, that all the islands of the Pacific Ocean can be divided into two great classes, the high islands and the low islands. All the high islands are of volcanic origin, while the low islands are of coral formation. It is the opinion of Dana, who has made a careful study of coral formations, especially in the Pacific, that in all probability even the low islands of the Pacific were originally volcanic, and that the deposits of coral had been made along their shores after their volcanoes had become extinct.

The islands of the Pacific, like the shores of the continents and most of their mountain ranges, extend in two great lines of trend, or general direction, which intersect each other nearly at right angles. These lines extend from the southeast to the northwest, and from the northeast to the southwest respectively, those extending in a general direction from southeast to northwest being the most common in the Pacific.

Now, perhaps, the greatest number of the earth's volcanoes are arranged along fissures, or cracks in the earth's crust. The craters are situated along the cracks, the openings being kept clear at the crater, and gradually closing elsewhere, probably by pressure. In other words, most of the volcanoes follow one another along more or less straight lines. For example, in the western part of South America they follow the Andes Mountains. A similar arrangement exists in the volcanoes of Central America, Mexico, and the United States. Now, this is especially true of mid-ocean volcanoes of the Pacific which lie along lines extending from southeast to northwest, or from northeast to southwest, though mainly along the former.

Some of the volcanic islands of the Pacific have already been described or referred to, as, for example, the Aleutian Islands, which stretch in a curved line from the southwestern extremity of the peninsula of Alaska to Kamtschatka on the coast of Asia. We have already described the island of Hawaii, the great volcanoes of the Sandwich Islands chain, and besides these there are in the North Pacific the Ladrone Islands, lying east of the Philippines.

Some of the principal remaining islands are: the Fejee Islands, which are volcanic, with numerous hot springs and craters. The Friendly Islands, with the peak of Tafua, 2,138 feet high, an active volcano with a large crater always burning, and two other volcanoes, Apia, and Upala. Tahiti, to the east, is at present extinct. One of its mountains, Orobena, said to be 10,000 feet high, has a crater on its summit. The Marquesas, still further to the east, are also volcanic. All of these islands lie generally in the lines of the northeast trend.

The Tongan or New Zealand Island chain extends in the direction of the northeast trend. This, as you will see, is the direction in which the two islands of New Zealand extend. The Tongan Island chain is continued to the south through Auckland and the Macquaire Islands to 58° S. Towards the north, in almost the same line, are the Kermadec Islands near 30° S.

There are several active volcanoes in New Zealand. An explosive eruption of Tarawera, in New Zealand, in 1883, continued for several days, and was followed, three days afterwards, by an outburst in an active volcano in the Bay of Plenty, and two months afterwards, by a violent outburst in a volcano on the island of Ninafou in the Tongan Islands.

Coming now to the Atlantic Ocean we find a number of volcanic mountains in the deep waters near mid-ocean. The principal of these, besides Iceland, are the Azores, the Canaries, Cape Verde Islands, Ascension Island, St. Helena Island, and Tristan d'Acunha. The Peak of Pico, in the Azores, rises to a height of 7,016 feet. The Peak of Teneriffe, in the Canaries, reaches the height of 12,225 feet. Teneriffe is a snow-capped mountain. It has a cone on its summit with precipitous walls like Vesuvius. Sulphurous vapors are continually formed at its summit, but no flames can be seen.

In the Cape Verde Islands is to be found the active volcanic mountain of Fuego, rising 7,000 feet above the sea. It has a central cone that has been broken down on one side like that of Somma on Vesuvius. Fuego was in eruption in 1785, and also in 1799.

Ascension Island, south of the equator, is formed entirely of volcanic materials. This island rises from an apparently granite floor on the bed of the ocean, in water 12,000 feet deep.

St. Helena lies further to the south. It is an extinct volcano, and has the remains of a crater on its summit with lava dikes in various parts of the island.

Tristan d'Acunha is an isolated mountain that lies in the South Atlantic, south of St. Helena, 1,500 miles from Africa, the nearest land. It is an extinct volcano that rises from a depth of 12,150 feet to a height of 7,000 feet above the sea. It has a truncated cone on its summit and a lake of pure water in its old crater.

There are only a few volcanic islands in the Indian Ocean. Kerguelen Island lies in the southern waters. St. Paul and Amsterdam to the north, lying near 40° S. lat., as well as the Crozet Islands, are extinct volcanoes.

In the Arctic Ocean is the volcanic island of Jan Mayen. In the Antarctic Ocean, as far as is known, there are only two volcanoes, Mt. Erebus and Mt. Terror. Mt. Erebus, 12,400 feet high, is an active volcano. Mt. Terror, 10,990 feet high, is an extinct volcano.