GEOLOGY. 7 



drusy crystals of carbonate of lime. The bird is supposed 

 to ■have been the "boatswain" (Phaeton mthereus,) which 

 resorts to the islands during the breeding season, and 

 makes its nest in the hoUows of the cliffs ; the bird in 

 this case being immured, during the period of incubation, 

 by some fresh deposit of sand, which had afterwards 

 hardened into the walls of its prison-house. Cases of 

 bones and eggs being found, have occurred in other parts 

 of the islands, imbedded in the limestone : and what may 

 be considered more singular, a gold knee buckle was said 

 to have been found not far from the Tanks on the Main 

 Island ; and a canister shot was dug up in coarse limestone, 

 whilst excavating the foundations for one part of the North 

 Bastion, across the bottom of the cavern. Turtle bones 

 have also been found in the loose sand of the sea beach ; 

 the turtles sharing the same fate as the bird before men- 

 tioned, being buried whilst depositing their eggs. Colonel 

 Nelson was informed by an eye-witness, that the dimen- 

 sions of- the skeletons of these animals were nine feet in 

 length and seven in breadth. He terminates his list of 

 animal organics by stating, that almost every shell known in 

 the surrounding sea may be found in the rock quite perfect. 

 As regards the Bermuda chalk deposit. Colonel Nelson 

 attributes its existence in this locality to the decomposition 

 of zoophjdjes, from the least calcareous to the large and 

 massiVe Meandrina and Astrea. He states that these 

 animals, and the many marine plants, consisting chiefly of 

 alime, produce this chalk, just as terrestrial animals and 

 ifsfregetables give carbon to soil when they decay. 



In various parts of the islands, rudely shaped cylindrical 

 blocks are to be found on the surface ; and of these well 



