226 bulletin: museum of cOxMparative zoology. 



rock is generally readily recognized as such. It is formed in fairly thick 

 layers, from two to six inches, and always dips toward the sea at a very 

 moderate angle, and has nothing in common with the eeolian strata 

 against which it abuts. Parts of it may be ground up again by a storm 

 should the calm between heavy surfs not continue sufficiently long for 

 it thoroughly to consolidate. 



All along the south shore one can find patches of beach rock dipping, 

 as observed by Professor Pace, to the sea at a slight angle, — the modern 

 beach rock of to-day, formed from the remodelling of the material thrown 

 up from the outer ledges. This beach rock is formed similarly to that 

 of the Florida Eeef, where it plays so important a part in its economj^, 

 while at tlie Bermudas it is of comparative insignificance. It is often 

 difficult to separate the beach rock from the base rock, but if, as I believe, 

 what is called "base rock" is only modified seolian rock, the latter has 

 Dot the importance attributed to it by Professors Rice and Heilprin. 

 On White Clifl:' Bay there are some a3olian cliffs dipping at a sharp 

 angle into the sea, showing remarkably well tlie transformation of the 

 thin aiolian layers into massive compact beds of base rock, in which the 

 dip of the strata can scarcely be detected, obliterated as it has been by 

 the cementing and solvent action of the sea water acting upon tliem. 



At Hungry Bay, Middleton Bay, and many points on the south shore, 

 and on the north shoi'e at Ireland Island, and on the north shore of St. 

 George, there are numerous localities where it is possible to observe the 

 transition of the inclined or horizontal feolian strata above high-water 

 mark to the solid ringing limestone characteristic of tlie "base rock." 

 On the shore of Godet Deep to the west of Heron Bay, at the foot of 

 Gibbs Hill, the " base rock," can be seen passing gradually from the a'olian 

 beds into the solidified ringing limestone characteristic of the intratidal 

 limits. The action of tlie sea cements the strata together, so that all 

 trace of their a-olian structure is lost. In many cases, however, we can 

 trace the continuation of the reolian stratification indistinctly, so that I 

 am inclined to consider what is termed "base rock" as due merely to 

 such cementing action of tlie sea; the more so, as similar {)henomcna 

 are clearly observable all along the Cuban coast on the shoi-e edge of 

 the elevated reefs between low and liigh water mark, where tliere is no 

 question of an underlying base rock. 



Professors Rice and Heilprin both speak of the "base rock" as dis- 

 tinguishing the old beacli formiition. ;ui'l as indicating the position of 

 the former sea i)order. It seems to nie tliat this basal rock is eeolian 

 rock which has become excessively indurated by the action of the sea 



