III. 



THE PHYSICAL HISTORY AND GEOLOGY OF THE 

 BERMUDA ISLANDS. 



The reefs, islands, and lagoons which together constitute 

 the Somers Archipelago cover an elliptical area, bearing 

 somewhat east of northeast, of about 220 square miles, 

 of which by far the greater part is occupied by water. The 

 land portion is confined almost wholly to the south and 

 southeast, where it makes a broken irregular crescent, some 

 fifteen miles in length, and from one to three miles in 

 width. Five principal islands, of which the largest, with 

 nearly 10,000 acres, contains approximately three-quarters of 

 the entire land surface exposed within the archipelago, are the 

 components of this crescent, about which are scattered some 

 two hundred or more islets and isolated rock-pinnacles. The 

 great body of water or lagoon, as it is sometimes called, which 

 lies north of this chain of islands, and is in direct communica- 

 tion with the open sea, is in a measure delimited by the ellipse 

 of the outer reef, which is wholly submerged even at low water, 

 except at two or three points, the most conspicuous of which is 

 at the North Rock. 



The depth of water in this outer lagoon is, in general, 

 about 40-50 feet, although, exceptionally, our sounding-line 

 dropped to 10 or 11 fathoms. For some little distance 

 before the outer reef is reached the water shallows to 20-30 

 feet, and at various spots within the open, serpula and mille- 

 pore growths rise to within a foot or so of the surface, or 

 even completely up to it, forming irregular oval patches, 

 which can be distinguished even at a distance by the discolor- 

 ation of the waters. 



