38 NOTES ON THE GEOLOGY OF THE BAHAMAS 



caves are often the result of the former action of the sea, and some of 

 them have probably been washed out by rain-water ; but in either case, 

 should a portion of the roof fall in, it would make a banana hole if 

 small, or, if large, an ocean hole like the one near Nicol's Town. The 

 horizontal passages are evidently washed out by water, but whether by 

 the sea or rain-water, I do not know, but I believe either might have 

 accomplished it. It is difficult to understand how underground chan- 

 nels could be formed under water, yet the boiling holes prove that such 

 exist ; but there is no means of determining whether they were formed 

 under the present circumstances or at some previous period when the 

 land might have been elevated. 



I was told that holes were as common under the water as they were 

 on the land, but did not myself observe this to be the case; but then 

 my opportunities for observation in this direction were limited. I infer 

 from the facts I have given that banana holes and caves pass gradually 

 into each other, and that they have been formed by the action of the 

 sea-water and afterwards modified by the action of rain-water, aided 

 by the products of the decomposing vegetable material and in some 

 cases by the falling-in of the roofs of the caves. 



Effects of Vegetation on the Surface 



One of the facts that I noticed shortly after my arrival in the Baha- 

 mas was the occurrence of great numbers of blocks of coral rock scat- 

 tered irregularly over the ground, and I first thought that they were 

 the result of the excessive erosion that I saw taking place around me. 

 But on some of the cays — as on Goat Cay, described above — where 

 the erosion was most rapid, there were no loose blocks, and if these 

 had been formed by erosion alone, it was there that we should have 

 found them most numerous. 



I had often noticed the gnarled and stunted appearance of the 

 bushes and trees that grew near the shore, and where there was evi- 

 dently a severe struggle between the sea on the one hand and the 

 plants on the other. 



At Quarantine Station I was shown a small bush, Rhacicallis 

 rupestris, and was told that it was over twenty-two years old, by a man 

 who said he could remember the plant as "long as he could remember 

 anything." I cut away the rock surrounding the bush, and found that 



