AGASSIZ: BAHAMAS. 41 



Nurse Cay, which is quite fertile, are bare, or support at best a very 

 scanty vegetatiou. 



From Nurse Channel the chain of cays continues toward the Great 

 Ragged Cays. We pass the white cliffs of Nurse Cay, with its low 

 aiolian hills forming a slightly midulating line on the horizon, separated 

 by a narrow channel from Buenavista Cay. Next come Racoon Cay and 

 Double-breasted Cay, all very bare of vegetation, with here and there a 

 long coral sand beach separating the low cliffs formed by the eating away 

 of the base of the aeolian hills which form this chain of cays. 



The disintegration of the formerly existing land masses, and their 

 breaking up into smaller masses or islands or islets, and finally rocks 

 and sunken banks, is also in great part a process not entirely due to the 

 mechanical action of the waves. Both the seolian and coral shore rocks 

 become most friable when saturated with sea water, so that large masses 

 are constantly sloughed off from the base of the hills which project into 

 the sea. These fragments of greater or less size are themselves rapidly 

 disintegrated by the same process, resulting in a coarse sand consisting 

 of oeolian or shore coi'al sand, which helps to form the small beaches so 

 frequently separating indistinct headlands marked by vertical cliffs. By 

 this process, beaches, small bights, or diminutive harbors may be formed 

 in the midst of faces of high or low cliffs, parts of which have been 

 affected more than others by the action of salt water. 



Ocean-Holes. 



Plate III. 



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 a3olian strata to the 

 same process which has on the shores of many islands formed pot- 

 holes, boiling holes, banana-holes, sea-holes, caverns, caves, sinks, cav- 

 ities, blow-holes, and other openings in the seolian rocks. Tliey are all 

 due more or less to the action of rain percolating througli tlie fcolian 

 rocks and becoming charged with carbonic acid, or rendered acid by the 

 fermentation of decomposed vegetable or animal matter or by the action 

 upon the limestone of sea water or spray under the most varying condi- 

 tions of elevation and of exposure. None of them have their upper 

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



