FLORIDA REEFS. 13 



We cannot therefore infer from the absence of organized beings in ancient 

 formations of this character, that they were deposited in a pekigic sea, des- 

 titute of life. This has ah^eadj been pointed out by Mr. Dana,* in his Keport 

 on the Coral Reefs of the Pacific. It must not, however, be supposed that 

 organic remains are wholly wanting in coral formations. There are, on the 

 contrary, localities where they are found in considerable numbers. In such 

 cases the action of the sea has probably been less violent, or in some 

 instances shells may have accumulated in such quantity, before being 

 cemented together, as to offer a certain resistance to destructive influences. 

 Occasionally also, delicate shells or sea-urchins may be lodged in the cavities 

 of coral stems, afterwards filled in with sand, and thus protected. 



We see everywhere that the larger boulders and the coarser fragments 

 have been the first to find a resting-place upon the dead reef; the minuter 

 particles and coral sand, which are periodically washed away from its crest 

 during heavy gales, never accumulating upon it till large boulders and 

 more solid materials have collected to such an extent as to form sufficient 

 protection for the more movable looser fragments. This fact is beautifully 

 illustrated by an accurate survey of Sand Key, Avliere a wide field of large 

 boulders is partially laid bare at low water, presenting the appearance of an 

 extensive key, with a low hill of minute materials, the product of some 

 heavy gale, heaped upon the summit, against which the sea plays without 

 disturbing it materially, even at high water, when it leaves in sight only 

 a nucleus, as it were, for a greater accumulation of such loose materials 

 which may in time cover the whole surface of the larger boulders. We 

 have here in reality the same phenomenon which is observed upon all 

 beaches, where larger materials have first accumulated on a shoal shore, 

 being followed, in the course of time, by more minute fragments which have 

 found a resting-place upon levels where the sea was powerless to increase 

 the collection of coarser matter. In attempting to understand these forma- 

 tions, it must be remembered that the accumulation of the larger materials, 

 collected at a certain level, may modify the action of the water at a sub- 

 sequent period, thus producing a combination of substances, heaped uncon- 

 formably upon each other. This is, in reality, the case throughout the 

 whole main range of keys, which have been raised to their present level 

 by the action of the tides and gales for ages past ; the fragments of which 

 they are composed having been thrown up at different periods, and over- 



* Geology of the United States Exploring Expedition. 



