GEOLOGY AND PALEONTOLOGY OP THE CANAL ZONE. 291 



on fiats submerged in geologically Recent time; (2) the amount of 

 the submergence of Cuba was about 100 feet. 



BAHAMAS. 



Alexander Agassiz has in his reconnaisance of the Bahamas 1 the 

 following very significant statement: 



May we not to a great extent measure the amount of subsidence which must have 

 taken place at certain points of the Bahamas by the depth attained in some of the 

 so-called ocean holes, as marked on the charts? Of course we assume that they were 

 due in the aeolian strata to the same process which has on the shores of many islands 

 formed potholes, boiling holes, banana holes, sea holes, caverns, caves, sinks, cavities, 

 blowholes, and other openings in the aeolian rocks. They are all due more or less to 

 the action of rain percolating through the aeolian rocks and becoming charged with 

 carbonic acid, or rendered acid by the fermentation of decomposed vegetable or ani- 

 mal matter or by the action upon the limestone of sea water or spray under the most 

 varying conditions of elevation and of exposure. None of them have their upper 

 openings below low-water mark, though some of them may reach many feet below 

 low-water level. Ocean holes were formed in a similar way at a time when that part 

 of the bank where they exist was above high-water mark, and at a sufficient height 

 above that point to include its deepest part. The subsidence of the bank has carried 

 the level of the mouth and of the bottom of the hole below high-water mark. 



From the description of the strata which crop out upon the banks in the vicinity of 

 some of_the ocean holes at Blue Hole Point, there seems to be little doubt that the 

 stratification characteristic of the aeolian rocks has been observed. 



The deepest of the holes mentioned by Agassiz has a depth of 38 

 fathoms, "in the extension of the line of Blossom Channel leading 

 from the Tongue of the Ocean up on the bank." 



I have had opportunities to study such "holes" or solution wells, 

 above sea level in Florida and have examined many of them, both 

 above and below sea level, in the Bahamas. Mr. E. W. Forsyth 

 sounded other "holes " and reported the results to me. 2 The depths of 

 the holes range from about 2 fathoms to as much as 33 fathoms, the 

 deepest hole in Fat Turtle Sound, North Bight, Andros Island, 

 sounded by Mr. Forsyth. As in my opinion Agassiz ; s deduction as 

 to the origin of these holes is incontrovertible, they indicate a stand 

 of the land during Pleistocene time at least 228 feet higher than at 

 present. Shattuck 3 and Miller accept a higher stand of 300 feet, 

 followed by submergence of 300 feet, and conclude that this move- 

 ment in strand-line position was followed by emergence, to an amount 

 between 15 and 20 feet. From my own experience in the Bahamas 

 the last change in the position of strand line was accompanied by 

 minor differential crustal movement. For instance, at Nicollstown 

 Light, Andros Island, a sea cave stands at such a height above the 

 sea as to show conclusively an elevation of 18 feet above the position 



i Mus. Comp. Zool. Bull., vol. 26, pp. 41-42, 1894. 



2 Vaughan, T. W., Carnegie Inst. Washington Yearbook No. 13, p. 229, 1915. 



3 Shattuck, G. B., and Miller, B. L., Physiography and geology of the Bahama Islands, The Bahama 

 Islands, pp. 19, 20, 1905. 



