206 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



careous cement, whilst the upward growth of Hving coral and the 

 accumulation of loose material on the surface proceed simultaneously. 

 Thus the work is ever in progress until it reaches the su.rface of the 

 water, the loose materials being either dispersed through the crevices 

 and interior of the reef, "packing" and rendering it solid, or else 

 carried out externally in the farther and lateral extension of the reef, 

 landward and seaward, so as to form wholly or in part the submarine 

 and compact basis on which the wind subsequently raises other masses 

 having their ovra peculiar stratification *, with a character very dif- 

 ferent as regards homogeneity, hardness, density, and organic remains 

 from that of the coral-reef basis. 



In Section 4, Capt. Nelson points out a few of the localities that 

 exhibit most clearly the character, source, and mode of aggregation of 

 the materials of the ordinary Bahama rock, such as is formed above 

 the sea level ; at the same time referring to the illustrative specimens 

 in the Bahama collection. For instance : — the south side of Silver 

 Cay and the beach extending westward from Nassau afford rolled 

 blocks, pebbles, and sand derived from the more massive corals, mixed 

 withremainsof Turtles, Fisii, Crustaceans, Echinoderms, andMoUuscs. 

 On the beach between Clifton Point and West Bay (specimen No. 1) 

 the shells of Strombus gigas more especially accompany the rolled 

 corals. At East Point (specimens Nos. 2 & 3) the sand is derived 

 from Corallines and NuUipores ; the finer sand being often in approxi- 

 mately spherical grains, though not so perfectly as at the White Cay 

 (specimen No. 4) and between Exuma and Long Cay. The beach near 

 Charlotteville Point (specimen No. 5) consists principally of Lucina 

 Pennsylvanica-^ in various stages of comminution. At Six Hills (Caicos 

 Group) the mass of Conch shells (St7'ombus gigas) is so great and suffi- 

 ciently cemented together as to form not only rock, but an island several 

 hundred feet in length:J:. Along the N.W. beach at Gun Cay (spe- 

 cimen No. 8), a hard, coarse, stratified rock is formed of Conch and 

 other shells, together with coral fragments. The large fragments of 

 corals and shells are never found much beyond the surf-range of high- 

 tide, and therefore always form rock at a low level ; whilst, on the 

 contrary, the fine calcareous sand is removed by the wind and depo- 

 sited in irregularly laminated beds, which, being consohdated in 

 various degrees, are converted into rock of different qualities §. 



counts of the process of the formation of coral-reef and coral-rock at Timor, 

 Sandalwood, Java, &c. as observed by Jukes and others. 



* See page 207. 



t See Bermuda Memoir, loe. cit. p. Ill {Venus Pennsylvanica). 



X A similar mass, about 60 feet long, 8 feet wide, and 8 feet high, occurs in 

 Harbour Island. This drift of shells was thrown up by the hurricane of 1845. 



§ See Bermuda Memoir, I. c. ; Proc. Geol. Soc. vol. ii. p. 160 ; and De la Beche's 

 Geological Observer, p. 230. It is to these beds, arranged by the agency of the 

 winds, that the author has applied the term " /EoUan " (see p. 201). They are of 

 more or less frequent occurrence, especially along sea-coasts, and Capt. Nelson has 

 particularly observed this formation at AlgoaBay and at other places on the coast 

 of South Africa, where they contain remains of existing land and marine molluscs, 

 &c., together with mammalian bones, including those of Man. Infusorial remains, 

 it is said, frequently enter largely into the composition of such accumulations, as in 

 the desert sands of Africa and Arabia. The ^Eolian rocks at Bermuda, Capt. Nelson 



