276 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



this subsidence. That tlie proto-Bermudian land was of elliptical shape, 

 and owed its existence to the action of winds sweeping over an extensive 

 coral beach, from which was gathered the material which now form the 

 solidified seohan hills of the Bermudas, no one can question. But there is 

 no evidence to show that the original annular coral reef was formed during 

 subsidence. That reef has disappeared, and nothuig is left of it except 

 the remnants of the seolian ledges, extending to sixteen or seventeen 

 fathoms outside of the reef ledge fiats, ledges which owed their existence 

 to the material derived from it, — the former seolian hills of the proto- 

 Bermudian land. Remnants of such ledges and former seolian hills are 

 the rocks forming the outer ledge flats, the breakers all along the south 

 shoi'e, the Mills Breaker, the !N"orth Rocks, the Chub Heads, the South- 

 west Breaker, and others. 



The evidence of the extent of the subsidence which has taken place at 

 the Bermudas is very clear. It is based upon the depth of the sounds 

 and of some parts of the lagoon, the existence of aeolian rock at a 

 depth of fifty feet below low-water mark, and the excavation of red 

 earth from a depth of forty-eight feet below low-water mark on Ireland 

 Island,^ and at eighteen feet below low-water mark in the entrance to 

 St. George Harbor. Numerous caves and caverns occur in the Bermu- 

 das, which have been fully described by previous writers. Many of them, 

 although extending far below low-water mark, could only have been 

 formed when the islands were at a greater elevation than at the present 

 day. In the caves, as well as smaller ponds or embryo sounds close to 

 the shores, the porosity of the seolian rock, as well as its cavernous and 

 honeycombed structure, is indicated by their connection with the sea. 

 The water rises and falls in the caverns with the tides, a.id the beat of 

 the diminutive waves against the subterraneous shores of the caves closely 

 follows that of the sea outside. 



1 Sir Wyville Thomson has given a section of the rocks exposed during the ex- 

 cavation for the basin of the dry dock at Ireland Island (Atlaiitic, I. 319.) Huge 

 stalactites and stalactites covered with Serpnlas extending below low-water mark 

 in some of the caverns clearly indicate the effects of the subsidence. Trunks of the 

 Bermuda cedar have been found in the red earth at a depth of forty-eight feet in 

 the excavation of the dry dock, and h;ive also been dredged from the bottom of 

 Hamillon Harbor in a depth of five fathoms. Tliis is of no great value as evidence, 

 since the stumps may have fallen in from the surrounding hillsides, have floated off, 

 and become water-logged. According to General Lefroy, one of the great bogs of 

 the main island extends to a depth of forty or fifty feet below the sea level, and 

 indicates the depth to wliich one of the sinks of the proto-Rernuidinn land renched 

 before the subsidence took place which resulted in the present configuration of 

 the islands. 



