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V. — On the Geology of the Bermudas. 



By RICHARD J. NELSON, Esq. Lieut. R.E. 

 Communicated by George Bellas Greenough, Esq., P.G.S. 



[Read April 23, 1834.] 



Having been stationed at the Bermudas, at different periods between the 

 years 1827 and 1833, I made a series of notes on the peculiarities of their 

 structure, and the following- memoir is the result. Much information was de- 

 rived from sources which are no longer accessible, such as the aspect and 

 arrangement of the strata, presented by large excavations made during the 

 progress of the works, conducted by the Royal Engineer Department, and 

 are either no longer in existence, or are masked by revetements* . 



Though the Bermudas are barren of mineralogical interest, they have yet 

 claims to attention in the striking lithological resemblance, which some of 

 their rocks bear to chalk and other secondary limestones ; and I hope that my 

 descriptions may afford a clue to the origin and nature of those formations. 

 Conceiving also that a comparison of the Bermudas with the coral islands in 

 the Pacific, described by Kotzebue, might be instructive, I have given refer- 

 ences to those passages in the work of that author, which present any ana- 

 logy or important variation. 



The Summer Isles, Somers' Islands, or Bermudas, (see Plate VI.) con- 

 sist of a group of about J 50 islets, lying within a space of fifteen miles by five, 

 and containing altogether nearly twenty-one square miles. This singular 

 little archipelago is situated very near, and conformably to, the south-east 

 side of an elongated ring of what are commonly called f coral reefs, and 

 rudely approaching the shape of an ellipse, twenty-five miles long by thirteen 

 broad. The direction of the group, as well as that of the major-axis of the 

 reef, to which it is parallel, is about north-east and south-west. Although of 

 a more regular form than any exhibited by Kotzebue, it bears a considerable 



* The collections formed by the author have been presented to the Museum of the Geological 

 Society of London, the United Service Museum, the Berlin Academy, and the Cabinet of Sir 

 John Tilden. 



t " Commonly called." This qualification is explained in pages 105 and 116, where it is sliown 

 that many reefs are formed by Serpulae. 



