The Hollow of the Atlantic.
It seems that the hollow of the Atlantic is not strictly a basin whose depth increases regularly toward the centre, the latest investigations showing that it is rather a saucer or dishlike one. so even is the contour of its bed. It is found that, proceeding westward from the Irish coast, the ocean bed deepens very gradually—in fact, for the first 230 miles the gradient is but six feet to the mile, though in the next twenty miles the fall is more than 9000 feel, so precipitous being this sudden descent that, in many places, depths of 1200 to 1600 fathoms are encountered in very close proximity to the 100 fathom line. With the depth of 1800 to 2000 fathoms the sea bed in this part of the Atlantic becomes a slightly undulating plain, whose gradients are so light as to show but little alteration of depth for some 1200 miles ; the extraordinary flatness of these submarine prairies, therefore, rendering the familiar idea of a basin rather inappropriate. The greatest depth in the Atlantic is claimed to have been found some ioo miles to the northward of the island of St. Thomas, where soundings of 3875 fathoms were obtained. The seas around Great Britain, instead of forming part of the Atlantic hollow, as heretofore generally regarded, are now alleged to be rather a part of the platform banks of the great European continent which the ocean has overflowed.