AGASSIZ : BERMUDAS. 245 



in shelves of very varying width, terminfiting either abruptly, or passing 

 into deeper water, eitlier l)y one or more steps, or by a gradual slope. 

 The slielf immediately above low-water mark is usually protected against 

 abrasion by species of Algje, or small barnacles, or patches of Serpulae 

 or Mvtilus, or a thin coating of NuUipores, while below or at low-water 

 mark Sargassum and coralline Algse begin to grow. 



It is easy to trace out on the chart the former connection of the flats 

 with the present land surfaces in all directions. The evidence obtained 

 from an examination of a number of ledge patches between the north 

 shore and the south side of the main ship channel is, most conclusive that 

 all these patches are only teolian ledges, parts of the clitls which once 

 were connected with that shore and have become separated from it by 

 causes similar to those now acting upon its cliffs. Upon these ledges 

 have gradually grown Algje, Corallines, a few Porites, Gorgonians, and 

 Millepores. When the patches are close to the shore Algre predominate. 



The shore cliffs extending into the sea usually have vertical or steep 

 faces, and one can readily follow their indented and honeycombed out- 

 lines to a depth of three to four fathoms or more, where the base of 

 the cliff passes abruptly into the coarse bank bottom. An examination 

 of the patches to the north of the main ship channel shows ledges with 

 tlie same structural features, excejit that their surface is more thickly 

 coated with corals, Corallines, and Alga^, as well as Millepores ; we find 

 also a few indistinct serpuline atolls on these patches, but their number 

 cannot be compared with those of the south shore. Many of the ledges 

 are only protected by small barnacles and Algae. Off Bailey's Beach 

 there is a row of isolated cliffs and ledges forming an outer barrier to 

 the bay, the remnants of the hills which once separated what now forms 

 Bailey's Bay from the sea. The interior patches of ledges are more iso- 

 lated ; they stand out vertically, or nearly so, in from five to six fathoms 

 of water, while those in deeper water nearer the outer belt of ledges may 

 be more or less choked and covered up by the masses of coralline and 

 *olian sand constantly accumulating and forming there. 



Some of the ledges which are not too far removed from the shore 

 line, like those off" Bailey's Beach or some parts of the north shore off 

 Spanish Point, are most instructive as showing ledges which still are 

 capi)ed by seoliau pinnacles, of which the aeolian stratificatif)n is most 

 distinct. In the submerged base of these pinnacles the stratification 

 has completely disappeared, and between high and low water mark the 

 seolian rock has been changed into a hard compact ringing limestone, 

 more or less worn and honeycombed by the solvent, as well as the 



