202 PROCEEDINGS OF THE GEOLOGICAL SOCIETY, 



action in the West Indies, as associated with coral-formations ; and 

 original contributions, respecting the West Indian Islands, by the 

 Hon. J. C. Lees, Lieut. C. C. Chesney, R.E., G. Cockburn, Esq., 

 Lieut. Warren, R.E., and Lieut. Grain, R.E. ; 9. Notices of the 

 neighbouring coasts of Cuba, Gulf of Mexico, Florida, &c. ; 10. 

 Notices of chalk and coral-reef at Barbadoes. 



Part IV. Miscellaneous. 



A. Relation of pinnacles and caverns, capes and bays, &c., and 

 other subjects in connection with the unequal distribution of mineral 

 matters in solution. B. Mangrove formations. C. Ripple-mark. 

 D. Fresh water in sand-banks and on beaches. E. Notices on Conchs, 

 as contributing to the formation of the chalk. F. Ideal restoration 

 of ancient lagoons. G. Poisonous corals and poisonous coral-eating 

 fish. H. On the use of such terms as "Animal" and "Vegetable." 

 I. Alligators; local extinction of races. J. Testacean reefs. K. Cata- 

 logues of the collections accompanying the Bermuda and Bahama 

 Memoirs. 



2. Geographical, topographical, and hydrographical notices. — 

 The Bahamas, or Lucaj^os, form a triangular group of islands, islets 

 or cays *, banks, and rocks, opposite and close to the northern mouth 

 of the Gulf of Mexico. This group may be inscribed in a nearly 

 right-angled triangle, whose sides are respectively about 900, 8.50, 

 and 350 geographical miles in length ; the hypothenuse -j* (900 



* Cay or Cays, a low island, corresponding to the Saxon " Holme." 

 t With regard to the hypothenuse of the right-angled triangle above-described, 

 Capt. Nelson observes that this line, whatever may have been its origin, together 

 with the two other sides, complete a Delta, which has been apparently thrown 

 down by the waters of the Gulf Stream on their receiving a check from those of 

 the Atlantic, as they emerge in full strength from the Gulf of Mexico ; just as 

 occurs at the moutns of the Nile, Ganges, Mississippi, &c., and of bar-rivers 

 and bar-harbours generally^. Although such deposits will be greatly accelerated 

 in formation, and gain much stabiUty, by finding ready-made hilly ground under 

 the sea, nevertheless they can be formed without this ; but, taking into account 

 the remarkably symmetrical relation between the sweep of the Bahamas and that 

 of the submarine mountain-range of the Leeward Islands (with which they form 

 a continuous S-like series), as well as the very general absence of shifting sands, 

 it may be surmised that the Bahama Delta has had the advantage of such ready- 

 made base and submarine nucleus of aggregation. The sweep of the eastern 

 current^ may have likewise assisted in the determination of the eastern boundary 

 of the hypothenuse. Capt. Nelson also remarks, that by the latest authorities ^ 

 it appears that the Gulf Stream is brought somewhat lower down in the maps 

 than formerly, as it just touches the southern end of the Newfoundland Banks, 

 and the origin of these last has been referred to the agency of the Gulf Stream. 

 As determining their position in concert with the St. Lawrence and Hudson's Bay 

 currents, the Gulf Stream may have had a considerable effect, but at so great a 

 distance northward we should rather look to the two former cm-rents for the sup- 

 ply of the materials ; and this view appears to be supported by the character of 

 the soundings. It is on these grounds that the Bahamas are here called the Gulf 

 Stream Delta. 



^ See Observations on River-bars, Phil. Mag. 4th Ser. vol. v. No. 32. p. 259 and 

 272. 



2 See A. K. Johnstone's Physical Atlas, pi. 6. 

 ^ See Johnstone's Atlas, /. c. 



