INTRODUCTORY CHAPTER. xxv 



presnmed that those black specks in the cement are merely frag- 

 ments of basaltic, or pumice stones If, however, the mixture I 

 have suggested should not consolidate, there might then be reason 

 to infer, that the calcareous matter laying on the rocks near Egg 

 island, may have undergone calcination, at the time the rocks 

 were in a state of fusion. 



Along the coast of St. Helena are many deep excavations, 

 forming caves, some of which are raised several feet above the 

 high water mark, and afford commodious retreats for fishermen 

 in rainy weather ; others are under the level of the lowest tides ; 

 consequently, there is a continual flux and reflux of water, occa- 

 sioned by the swell of the sea, which in the course of time has 

 penetrated very far into the base of the island. 



It would be impossible to explore these cavernous holes, be- 

 cause the swell rises, at every ingress, to the top of the entrance ; 

 which of course excludes all external air ; and the internal air 

 being powerfully compressed by the rushing in of the water, 

 produces, by its re-action, a very singular effect. On the perpen- 

 dicular cliff, forming the coast opposite to Egg Island, there are 

 two or three very curious jets d'eau. By the compression of air 

 within the caverns, where they are probably more enlarged than 

 at the exterior openings, it appears that the waters must have 

 gradually perforated amongst the cracks and fissures, vertical, or 

 more probably, oblique, and irregular passages within, and 

 behind, the exterior rocks. The orifices of those passages appear 

 on the face of the cliff at the height of 60 or 70 feet above the 

 sea ; from which I observed the water to spout, exactly like the 

 blowing of a whale, and, at intervals, corresponding with the 

 times of the rise and fall of the swell. 



On the northern coast, at Munden's cove, and also to the east- 

 "ward of Rupert's Valley, at a considerable height above the sea, 



e 



