AGASSIZ: BERMUDAS. 249 



appear to have their limit at a much less depth, in from five to seven 

 fathoms. Beyond this depth the broken ground sets in, which the fish- 

 ermen state that they can trace to seventeen or even twenty fathoms. 



The ledges on the sides of the causeway connecting .St. George with 

 the hills to the east of Harrington Sound, together with the flats which 

 connect them, indicate the former existence of a chain of hills which have 

 been disintegrated. These flats form the platform of the east and north 

 sides of Castle Harbor, and they give us an explanation of the sand 

 flats to the westward of Ireland Island. The causeway flats are literally 

 packed with coralline Algae. 



To the northwest of Western Blue Cut there is a stretch of coral 

 covered ledges, which, like the ledges to the north and east of a line run- 

 ning west of Ireland Island, are somewhat isolated, and have remained 

 disconnected from other ledge flats. They have not, like the Devil's 

 Flat, and those to the westward and southwestward of them, been 

 pounded and ground up to form coarse sand ledge flats with steep 

 slopes, from the surface of which scattered reolian ledges barely project 

 high enough to allow a scanty growth of Millepores and Gorgonians. 



On the inner side of the reef massive corals do not as a rule seem to 

 exist beyond four to six fathoms, the point at which the great expanses 

 of coralline bottom begin, and which extend nearly unbroken to the great- 

 est depths of the inner waters on the banks. 



The greatest width of the belt in which corals grow from the inner 

 edge of these flats or patches to the outer six or seven fathom limit is 

 about three miles at the eastern extremity. This is nearly the width of 

 the land and water belt included between the island of St. George and the 

 entrance to Castle Harbor. The belt between Ireland Island and Gibbs 

 Hill is however considerably wider than any of the ledge flats. At the 

 western end it is not more than a mile, the ring of ledge flats being wid- 

 est west of Mills Breakers, and diminishing towards North Rock. The 

 ledge flats are much narrower along the whole western and southwestern 

 face of the Bermudas. The gradual shelving slope of the ledges which 

 have been abraded on the sea face of the flats is well seen between the 

 entrance to Hogfish Cut and the Western Blue Cuts. The Little Bar 

 and Chaddock Bar form two wide spits with a gradual slope from two 

 to seven fathoms, covered by Gorgonians, Corals, Millepores, and Algse. 

 Long Bar is a similar ledge, separated however from the "Western LedLre 

 Flats by a channel of from six to seven fathoms, the bottom of which 

 is covered with corals and the attendant Alga? and Sarcrassum. These 

 bars are full of just such ledges as have been described, only they have 



