4 COLLINS AND HERVET. 



below the surface it was the ordinary soft limestone; then to 695 feet, 

 earthy, decomposed lava, in the lower part of the range with frag- 

 ments of solid lava, sometimes waterwom; then to 1413 feet, the 

 lowest point reached, solid lava. Considering these data in connec- 

 tion with our knowledge of the present under-water Bermuda, the 

 slope from the present island to the ocean floor, the conclusion is 

 reached that a great volcanic cone was formed, perhaps in the early 

 Eocene, with its summit where the present island is, rising about 

 11,000 feet above the sea. The 718 feet above the bottom of the 

 boring and an unknown distance below consist of the unchanged lava 

 of the cone; the 315 feet laj'er above this was produced by the dis- 

 integration of the upper part of the cone; the foraminifera found in 

 the 380 feet of limestone indicate that its formation, by the same 

 processes that are now at work, began before the end of the Eocene; 

 while the occurrence of the limestone 245 feet, and the decomposed 

 lava 560 feet below sea level, indicate a long-continued subsidence. 



At the present time there are no bodies of fresh water on the islands; 

 rain water sinks almost immediately into the porous soU, which is 

 also honeycombed by large and small caves and passages; brackish 

 water can be obtained at sea level anywhere, but strictly fresh water 

 nowhere. A curious instance of this permeability was told us by Mr. 

 Reid Trott, owner of the aquarium known as the Devil's Hole; this 

 is on the shore of Harrington Sound, distant a quarter of a mile, rather 

 high ground, from the south shore; in a southerly storm the surf is 

 very heavy on the south shore, and white from the fine lime of the 

 beaches; within a day or two the water in the aquarium becomes 

 milky. The only visible outlet of Harrington Sound is by the nar- 

 row passage at Flatts Bridge; but though the rise and fall of the 

 tide in the Sound is only a few inches, it has been calculated that it 

 represents a flow through unseen passages of much more than passes 

 under the bridge. Devonshire Marsh forms a sort of bowl, with 

 higher ground on all sides; surface drainage into this fills the ditches 

 with practically pure fresh water after rains, but it soon disappears, 

 and only a few species of fresh water algae are able to avail themselves 

 of the short opportunity.* 



A few species of " Fucus " are mentioned by Turner, Icones Fucorum, 

 1808-1819, but actually our knowledge of the algae of Bermuda 



2 A * is placed before the name of each fresh water or terrestrial species 

 listed, including some Mjrxophyoeae found here within range of tides, though 

 not normally marine. 



