NOTE.--The light tint indicates sea less than 1,000 fathoms deep. The dark tint ,, ,, more than 1,000 fathoms deep. The figures show the depth in fathoms. Soundings were taken by the _Challenger_ in four {264} different directions around Bermuda, and always showed a rapid deepening of the sea to about 2,500 fathoms. This was so remarkable, that in his reports to the Admiralty, Captain Nares spoke of Bermuda as "a solitary peak rising abruptly from a base only 120 miles in diameter;" and in another place as "an isolated peak rising abruptly from a very small base." These expressions show that Bermuda is looked upon as a typical example of an "oceanic peak"; and on examining the series of official reports of the _Challenger_ soundings, I can find no similar case, although some coasts, both of continents and islands, descend more abruptly. In order to show, therefore, what is the real character of this peak, I have drawn a section of it on a true scale from the soundings taken in a north and south direction where the descent is steepest. It will be seen that the slope is on both sides very easy, being 1 in 16 on the south, and 1 in 19 on the north. The portion nearest the islands will slope more rapidly, perhaps reaching in places 1 in 10; but even this is not steeper than many country roads in hilly countries, while the remainder would be a hardly perceptible slope. Although generally very low, some parts of these islands rise to 250 feet above the sea-level, consisting of various kinds of limestone rock, sometimes soft and friable, but often very hard and even crystalline. It consists of beds which sometimes dip as much as 30deg, and which also show great contortions, so that at first sight the islands appear to exhibit on a small scale the phenomena of a disturbed Palaeozoic district. It has however long been known that these rocks are all due to the wind, {265} which blows up the fine calcareous sand, the product of the disintegration of coral, shells, serpulae, and other organisms, forming sand-hills forty and fifty feet high, which move gradually along, overwhelming the lower tracts of land behind them. These are consolidated by the percolation of rain-water, which dissolves some of the lime from the more porous tracts and deposits it lower down, filling every fissure with stalagmite. [Illustration: SECTION OF BERMUDA AND ADJACENT SEA BOTTOM. The figures show the depth in fathoms at fifty-five miles north and forty-six miles south of the islands respectively.]