228 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



Thomson's view, 1 that the Bermuda limestone is entirely seolian, and 

 that the base rock does not underlie the softer seolian rock, 2 but to 

 modify it by the above statement regarding the formation of base rock 

 and of beach rock as now forming mainly from the remodelling of older 

 material. 



Rice accepts the Agers Island strata as beach rock, as well as the stra- 

 tum at the south end of Ireland, a statement from which I must most 

 emphatically differ. These beds contain marine shells in seolian strata. 

 The base rock of the islands of Hamilton Harbor appears, as far as I have 

 observed it, to be due to the induration of the lower strata of the seolian 

 rock exposed to the action of the sea. There are but few islands in 

 Hamilton Harbor of which the seolian strata do not dip at a considerable 

 angle towards the low-water mark line into the sea. It is true that in 

 some cases there are also seolian rock strata parallel with the sea, every- 

 where lying nearly, if not quite, horizontal, but these strata present the 

 character of seolian rocks modified by the action of the sea. 



On Grace Island, Hawkins Island, and off the Quarantine in Hamil- 

 ton Harbor, we traced most distinctly, at low-water mark, seolian strata 

 dipping at a high angle into the sea, and yet at many points they have 

 passed into what is called base rock by the complete obliteration of the 

 knife-edged strata from the abrading, the cementing, and the solvent 

 action of the sea. The third island south of the Quarantine, Post Island, 

 and Darrel Island all present the same phenomena of modification of the 

 seolian rock into base rock. In the interior of a cavern leading into 

 Quarantine Island we could trace the dip of the seolian rocks into the 

 sea, and the same was the case at Hanson's Island. On the southwest 

 side of Post Island the fine seolian lamination could still readily be 

 detected below high- water mark through the " base rock " coating. 



Nowhere in the Bermudas have I found corals above high-water mark 

 or higher, the presence of which could not be accounted for by the action 

 of high winds or waves during hurricanes, and surely the presence of 

 caves above high-water mark is not in a limestone district an indication 

 of elevation. If the explanation I have given of the formation of base 

 rock is correct, its existence at a height of a few feet above high-water 

 mark is not a proof of elevation. 



1 Thomson, Atlantic, I. 307. 



2 Tliere was no "base rock" found while cutting through the seolian strata 

 during the excavation of the Ireland Island Dry Dock. 



