274 bulletin: museum of comparative zoology. 



south. The third is the Murray Anchorage sound, limited on the west 

 by the Bailey Bay Flats, on the north and east by the Three Hill 

 Shoals and the flats west of Mills Breaker. The third sound opened by a 

 narrow deep valley (the Ship Channel) towards the sea, and communicated 

 by a wide passage with the fourth sound, bounded by the ledge flats of the 

 northwestern part of the Bermudas, — flats which extend unbroken from 

 the north of Western Blue Cut to the Eastern Ledge Flats, — and on the 

 southern edge by the line of the Three Hill Shoals and by the western 

 extension of the Bailey Bay Flats. This fourth sound is in reality a 

 double sound, as the western part is separated from the eastern by a 

 narrow line of eeolian heads, indicating probably the position of a cross 

 line of dunes connecting the Ledge Flats and Bailey Bay Flats. Its 

 northern edge was deeply indented, as is indicated by the many tongues 

 of deep water cutting into the width of the ledge flats (Plate II.). Two 

 smaller and indistinctly connected sounds are similarly indicated to 

 the west of East Ledge Flats and to the west of Mills Breaker. On the 

 eastern ledge flats there are also a number of deep pockets, already re- 

 ferred to, as well as many deep bights running into the ledge flats, 

 indicating the position of valleys running more or less at right angles 

 to the trend of the ledge flats. 



The Southwest Breaker aud Chaddock, Little, and Long Bars are the 

 base of lines of seolian hills, once running parallel with the edge of the 

 western and southern Ledge Flats hills. 



This proto-Bermudian land must have resembled the Bermudian land- 

 scape of to-day, and has been reduced to its present condition by the 

 same causes which we see at work to-day on the islands of the group, and 

 which have acted more vigm*ously either on the faces most exposed to 

 the prevailing winds, or upon seolian hills of a lower altitude than those 

 of the main island. 1 The proto-Bermudian sounds vary in depth from 

 six to twelve or thirteen fathoms, the deepest being the sound to the 

 north of Three Hill Shoal. 



I also agree with Rice and Heilprin that the amount of subsidence 

 must have been " sufficient to account for the depth of water which 

 marks the lagoon and inner sounds," and that " before this subsidence 

 took place probably the entire area now covered by the Bermudian 



1 " The prevalence of powerful winds on the south side would tend to elevate this 

 side of the island, while the opposite side, not feeling this influence in any marked 

 degree, would remain comparatively low and flat. In a period of subsidence the 

 low side would naturally he the first to succumb to the waters, and would undergo 

 suhmergence long before the elevated slopes. And this is precisely what appears 

 to have taken place in the Bermudas." — Heilprin, Bermudas, p. 42. 



