But what forms, perhaps, one of the best instances of a large island formed by submarine eruptions during historical times, is Bogosloff Island in Behring Sea, some forty miles west of Unalaska Island. This island, the position of which is seen on the accompanying map, is known to the Russians as Ioanna Bogoslova, or St. John the Theologian. It is situated in lat. 53° 58' N., long. 168° west. It is said that during the year 1795, some of the natives of Unalaska Island saw what they thought was a fog in the neighborhood of a small rock, which they had known for a long time to project above the sea in these waters. This rock was marked on some Russian chart dated 1768-69. It was seen by Captain Cooke, in 1778, and was named by him Ship Rock. But it was not a fog that the Unalaskans had seen in the neighborhood of Ship Rock; for, to their great surprise, the fog continued in sight although everywhere else the air was quite clear. Of course, this was a great mystery to the people. During the spring of 1796, one of them, who possessed either greater curiosity than the rest, or greater courage, or both, visited the rock. He returned, telling the strange story that all the ocean around the rock was boiling, and that the mist or fog was caused by the rising steam. What was taking place was a submarine eruption. During May, 1796, sufficient matter had been brought up from below to increase greatly the area of the small rock. [Illustration: FIG. 23. ALEUTIAN ISLANDS] During later years several attempts have been made to visit Bogosloff Island. For example, the island was visited during 1872 and 1873, when it was found to have increased in height to 850 feet. But no appearance of any volcanic crater was to be seen. During October, 1883, a great volcanic eruption occurred there. Considerable changes were produced in its shape, as well as in the depth of the surrounding water. During this eruption, clouds of steam completely hid the island. Great quantities of ashes obscured the light of the sun. After the eruption, a new island was thrown up near the old one, in a place where the water had previously been deep enough for the ready passage of ships. The new island was about half a mile from the old one. It was conical in form, from 500 to 800 feet in height, and about three-quarters of a mile in diameter. The new island was visited in 1884 by the U. S. Revenue Marine Steamer _Corwin_. Lieutenant Cartwell, who visited the island at this time, described it as follows: