San Felix and San Ambrosio are volcanic islands in the South Pacific Ocean, San Felix being situated in latitude 26° 15′ south and longitude 80° 7′ west of Greenwich and San Ambrosio lying about 16 kilometers to the east-southeast (figure 1). They are about 500 miles west of Chañaral, on the coast of Chile, and the same distance due north of the group of Juan Fernandez and Mas-a-fuera. The South Pacific charts show several known rocks or islets and some whose existence is recorded as doubtful, which, with the above-named islands, form an archipelago strewn on a narrow submarine ridge that extends along the meridian of 80 degrees west from about 36 degrees south to 26 degrees south, the ridge being defined by the 2,000-meter contour line. Knowing that all these islands and islets are the peaks of volcanoes, we may . . .