AGASSIZ : BERMUDAS. 239 



thickness to conceal the original ledges, and perhaps in many cases to 

 build them up from a couple of fathoms or so to within the limits of 

 low-water mark. Their growth can in no way be compared to the mas- 

 sive coral reef structures we hud in the West Indies and Florida. 



Off the north, as well as off the south shore, the patches nearest the 

 land are merely ledges consisting of larger or smaller pieces which have 

 become separated from the shore cliffs by the action of the sea, or else 

 they are more extensive patches marking the position of small islands, 

 islets, or rocks which were once more or less closely connected with the 

 main island, and which now run as ledges parallel to the shore line. 

 These ledges, if close to the shore, are barely covered by Algse and a few 

 barnacles, or Mytilus, or isolated corals, or such animals and plants as 

 we find on the immediate shore line. Farther from the shore they be- 

 come overgrown with a greater profusion of Alga? and Nullipores. As 

 we proceed from the north shore to the ship channel, we gradually come 

 upon ledges on which are found corals and Gorgonians, Algae and Nulli- 

 pores occurring as on the ledge flats, but in less profusion. It is on 

 the outer ledge flats, which have probably been under water longest, 

 that we find the most abundant growth of corals. While I do not deny 

 that some of the ledges have been increased in height, and slightly in 

 width, by the corals covering them, yet the corals have played but an 

 insignificant part in building up the ledges themselves. The ledge flats 

 are the remnants of the proto-Bermudian seolian laud worn down by 

 the action of the sea to a certain level, and upon these eeolian ledges 

 forming the underlying foundation of all the patches, the coral reefs — 

 viz. corals, Corallines, Gorgonians, and Algse — have grown, but only as 

 a comparatively thin veneer upon the pre-existing aeolian ledges. 



The surface of many of the ledges outside of Hungry Bay on the 

 south shore, exposed at low water, is covered with coral growth, espe- 

 cially the ledges on the iuner face of the outer patches of the south 

 shore reef. The ledges exposed at extreme low water are irregularly 

 shaped, rising from two to four fathoms of water ; they are greatlv under- 

 cut and abraded, and show signs of the solvent action of the sea. The 

 vertical and sloping faces of the ledges near shore are covered and pro- 

 tected from wear by a thick growth of Alga? and Corallines, similar to 

 the growth which protects the upper face of the ledges. But on the upper 

 surface there is in addition an abundant growth of Serpnlre. Between 

 the outer ledges and the shore, more or less protected by the isolated 

 outer patches extending to the reef, a sort of lagoon is formed. In this 

 lagoon are found numerous ledges ; then, closer to the shore, overgrown 



