DEPARTMENT OF MARINE BIOLOGY. 



231 



depth of 8 fathoms or somewhat more. A series of somidings, undertaken east 

 of South Bight from off Bastian Point to off Sharp Rock Point, clearly showed 

 a platform ranging in depth from about 9 fathoms on its landward side to a 

 depth of about 13 fathoms on its seaward edge, where there is a rapid slope to 

 20 fathoms or more and a steeper declivity into depths exceeding 100 fathoms. 

 This outer submerged terrace can be traced along most of the eastern face 

 of the Andros barrier reef; it is greatly developed on the north side of New 

 Providence Island, especially seaward of Hog Island, and on the east side of 

 the Berry Islands. In fact, this submerged terrace is one of the salient sub- 

 marine physiographic features of the Great Bahama Bank. 



Fig. 7. — Bethel Entrance, Andros Island, Bahamas. 



Position of light, Lat. 26° S" N., Long. 78° 0' 30" W. From a plane-table survey by 

 Alfred G. Mayer, May 1914. 



As other "blue holes" attain a depth as great as 33 fathoms, a submarine 

 shelf at that or a slightly greater depth might be expected, but the hydro- 

 graphic work necessary to ascertain whether such a platform exists has not 

 been done. 



In my paper entitled "The building of the Marquesas and Tortugas atolls, 

 etc.,"^ I presented evidence which led to the conclusion that the Tortugas atoll 



'Carnegie Inst. Wash. Pub. 182, pp. 57-67, 1914. 



