106 



Lieut. Nelson on the Geology of the Bermudas. 



Geological Details of the principal Islands in Geographical Order *, 



St. George's Island. — The strata dip southward with considerable uniformity along the southern 

 and eastern shores, which are protected from violent attacks of the sea by St. David's, Smith's, 

 and Longbird islands; and by the reefs which bound the intricate passage into Murray's 

 Anchorage. 



The north side is exposed, throughout its whole length, to the fury of a sea which has had, 

 within the area of the north reef, a distance of seven or eight miles, sufficient space to re- 

 accumulate its destructive energies ; and exhibits in the cliffs the saddle or dome-shaped structure, 

 (variously exemplified in figs. 1 and 2,) the lines of lamination dipping towards every point of the 

 compass. In one or two instances, the summits of what were once internal hills, are bared, and 

 within a few square yards the coats of this nucleus range round it with perfect regularity. As 

 might be expected, this north side consists, in a great measure, of abrupt cliffs, and landslips 

 brought down by the undermining of the waves. 



Fig. 1. Sections at tlie summit of Retreat Hill. 



This section is at rigid angles to Fig. 1, tJic imiats (a) coinciding. 



The sandstone on the summit of some of the hills, is scarcely tenacious enough to hold together ; 

 but from Mullet Bay to the ferry, on a level of not more than twenty feet above the sea, the rock 

 suddenly becomes a very hard, fine-grained or compact limestone, in which scarcely a vestige 

 of organic structure is visible. 



Just above high-water mark, along a considerable portion of the south side, is a stratum of 

 calcareous sand, about six feet thick, apparently a distinct deposit from the rock above it. 



Vertical crevices abound, filled with a substalagmitef much harder than the rock. In some places 

 the arrangement of these cavities resembles that of veins in old slate or limestone. Where the 

 partitions stand comparatively unimpaired by the weather, their planes constantly intersect one 

 another, and thus form reticulations, once filled with the soft sandstone. In all cases the 

 veins are younger than the crevices, from whatever cause these last may have originated. 



St. David's. — Like St. George's, this island consists of a low, irregular belt of hard limestone 



* Map, Plate VI. 



t I have employed this word to designate uncrystallized calcareous incrustations and deposits; 

 whilst I have retained the word 'stalagmite' to describe such as are crystallized. 



