In the first place, then, the testimony of the deep-sea soundings maybe summarized in a few words. Thanks chiefly to the expeditions of theBritish and American gunboats, "Challenger" and "Dolphin" (thoughGermany also was associated in this scientific exploration) the bed ofthe whole Atlantic Ocean is now mapped out, with the result that animmense bank or ridge of great elevation is shewn to exist inmid-Atlantic. This ridge stretches in a south-westerly direction fromabout fifty degrees north towards the coast of South America, then ina south-easterly direction towards the coast of Africa, changing itsdirection again about Ascension Island, and running due south toTristan d'Acunha. The ridge rises almost sheer about 9,000 feet fromthe ocean depths around it, while the Azores, St. Paul, Ascension, andTristan d'Acunha are the peaks of this land which still remain abovewater. A line of 3,500 fathoms, or say, 21,000 feet, is required tosound the deepest parts of the Atlantic, but the higher parts of theridge are only a hundred to a few hundred fathoms beneath the sea.