AGASSIZ: BERMUDAS. 241 



ino- to their position, the depths in which they are found have been 

 transformed into the peculiar agglomeration of reefs and ledges off the 

 south shore. They form an incipient ledge flat, as it were, of which 

 the outer line is still very prominent, and which the outer breakers 

 have not as yet undermined and eaten away, so as to leave, as they 

 do round the ledge flats, only a few isolated rocks cropping to the sur- 

 face. Some of these ledges are a hundred and fifty feet in length, and 

 even more, with a breadth exposed at low water varying from two or 

 three feet to thirty or forty feet ; others are only small pinnacles a few 

 feet in diameter. All, however, present nearly vertical faces, and rise 

 abruptly from two and a half to four fathoms. They are all more 

 or less undercut, eaten away, of irregular mushroom shape, and the 

 breaking up and disintegration of the exposed pinnacles after they 

 have been so undermined as to break from their base supply a large 

 amount of the material thrown up on the beaches. 



A section along the slope of the sea beach of the south side of the 

 island shows first a shore line of flats, ledges, and pinnacles, then a sec- 

 ond or a third row of mushroom-shaped undercut rocks, some reaching 

 to above low-water mark, others barely awash, or a few feet below. A 

 few of the ledges may still be surmounted by seolian rock pinnacles, 

 while the submerged surface of other flats is either protected by Algre, 

 Corallines, or Serpula?, and according to their depth they are changing 

 or have been changed into serpuline reefs. A few of the ledges in 

 deeper water inside of the outer line of ledges are covered with corals 

 and Gorgonians. The outer row of ledges forming the reef do not 

 differ from the rows of rocky ledges inside of the reefs, or from those 

 close to the shore. There are on the outer lines, however, no ledges 

 surmounted by pinnacles, most of them having been changed into boil- 

 ers, or into long ledges with winding or S-shaped vertical walls, the sur- 

 face of which is protected by Algse, Serpulse, and other growths. Outside 

 of the outer row of ledges we come upon the broken ground bottom, 

 which consists of flat ledges extending from five to fifteen or more 

 fathoms. Upon these in the shallower parts flourish the massive corals 

 and Gorgonians, while over the deeper parts extend mainly the Gorgonians 

 and Algse, as well as Corallines. Such broken ground bottom occurs off 

 Chaddock Bar, off Long and Little Bar, off the Chub Heads, and all the 

 way from the Southwest Breaker outside of the south shore reef to off 

 Castle Harbor and off St. David Head. Similar broken ground occurs 

 wherever on the Admiralty Chart it is marked r, — off the Mills Breaker 

 Channel, outside of the North Bock Channel, the Eastern and Western 



VOL. XXVI. — NO. 2. 16 



