118 TRANSACTIONS OF THE [jAN. 18, 



excavation, fifty feet below tide, on Castle harbor at ten feet 

 above tide and near the Harrington house at fifty feet above 

 tide. Certainly there is no reason to suppose that the Harring- 

 ton House exposure was ever below tide level. The absolute 

 consolidation of the rock at many exposures resembles that of 

 some Pahieozoic limestones, but its structure and the absence of 

 marine fossils forbid any supposition of marine origin. The 

 suggestion that seawater caused the consolidation is unneces- 

 sar}^, as the sandstone, in one locality at least, is thoroughly 

 consolidated at eighty feet above tide. 



Evidently the limestone was consolidated soon after its forma- 

 tion. A long period elapsed with it as the surface rock, during 

 which the conditions were very different from the present, were 

 rather those which one finds in ordinary limestone regions. 

 Springs and streams must have been common features; subter- 

 ranean drainage made caverns, which collapsing gave large and 

 small "sinks" like the "banana holes" of to-day. Residual 

 claj's formed red soil on which plants grew and Helix flourished. 

 During this time many of the basins of the reef and lagoon must 

 have been outlined. 



If the area was annular originally, the enclosed lagoon must 

 have been filled up with the limestone during a period marked 

 apparently by little change. 



A period of subsidence followed, during which the waves 

 acted upon new rock strips brought within their reach and some 

 of the sand was blown over on the old surface, as is shown in the 

 Ireland island excavation. As the subsidence continued, beach 

 rock encroached upon the new ji?olian formation, giving the " coral 

 crust " of Ireland island and the lower portions of the deposits 

 on the isthmus between Ireland and Hamilton islands. The 

 beach accumulations seen at many places along the south shore 

 and on St. George, usually as a thin deposit resting on the lime- 

 stone, and often associated with the intermediate clay deposit or 

 covering the old limestone surface, occur at practically the same 

 level as the deposits within the " hook," where the conditions are 

 not unlike those seen elsewhere; for in deepening Stag Channel 

 off Ireland island, red clay was found associated with the marine 

 limestone. 



The relations of this beach rock are such that one finds diflft- 

 culty in conceiving how they could come about with nothing 

 more than a mere interruption of the subsidence. On some of 

 the islands within the " hook " and on the Ireland isthmus the 

 rock is two or three feet above water. The sandstone overlies it 

 and passes down over its surface to certainly sixteen feet below 

 water line in Two-rock channel and in such fashion as to suggest 



