AGASSIZ : BERMUDAS. 215 



Professor Heilprin is of the opinion that perhaps the natural arches at 

 Tuckerstown were formed at a time when the relations of land and water 

 were different from what they are now ; though it is difficult to ascertain 

 precisely what his views are. Here, as at the Bahamas, many sinks occur 

 in which, owing to the porosity of the rock, but little water can remain; 

 if the sinks are at some height above the sea level, this undoubtedly per- 

 meates the interior of the island, and whenever the sinks reach below 

 the level of the sea they are filled with brackish water. There is very 

 little difference in the appearance of the rocks "composing the islands. 

 We have by no means the variety in the appearance .of the agolian rocks 

 met with in different islands of the Bahamas. 



Solution has undoubtedly played some part in producing many of the 

 fantastic spires of seolian i*ocks one meets in the Bahamas and Bermudas. 

 The undermining of the shore cliffs, the mushroom shape of many of 

 the isolated rocks and shore ledges, both above and below low-water 

 mark, is in part due to the solvent action of sea water. This is 

 especially well seen in the Bahamas on every island or islet at many of 

 the channels leading from the sea face on to the bank. 1 On the Ber- 

 mudas this is perhaps best seen in the formation of the pinnacles in the 

 comparatively quiet waters of Mullet Bay and of Castle Harbor, and in 

 the undermining of all the shore cliffs and the cavernous and honey- 

 combed condition of the older ledge patches between the islands and the 

 reef flats and those of the ledge flats themselves. Close to the Causeway 

 at the northwest part of Castle Harbor there is quite a patch of low pin- 

 nacles from two to two and a half feet in height, which seem to show an 

 active solvent action by the sea. 



But the solvent action of the salt water cannot be compared in effi- 

 ciency with the destructive mechanical action of the sea ; the latter has 

 to a great extent been arrested by the covering coat of Gorgonians, Mille- 

 pores, Algse, and Corallines, as well as of the more massive corals found 

 thriving upon the heads, patches, ledges, and ledge flats of the inner and 

 outer waters of the Bermudas. But these heads, ledges, etc. do not, as has 

 been stated by former observers, owe their existence and their gradual 

 increase to the corals, as they consist of seolian rock with only a protect- 

 ing veneer of corals over their surface, constituting a coral growth, and 

 not a coral reef. 



In the region of the Everglades of Florida, 2 the process of solution of 



1 See A. Agassiz, The Bahamas, Bull. Mus. Comp. Zool., Vol. XXVI. No. 1, 

 1894, p. 49. 



2 The Topography of Florida, by N. S. Shaler, Bull. Mus. Comp. Zool , Vol. XVI. 



