ON THE GllOI.OGY OF JIAIUJADOS. 207 



would appear to be connected with the set of the currents, and 

 possibly with the suppl}- of food. The main current is directed 

 westwards, while the shore recedes northwards round Oistin's Bay. 

 As a matter of fact, very little coral grows in this bay, the bottom 

 })eing everywhere marked as sand, except at a few depths between 

 ;iU and GO fathoms where coral is recorded (probably broken frag- 

 ments or else species which are not reef-builders). 



The case is much the same in and outside Carlisle Bay, at the 

 south-western corner of the island, for, although coral is recorded 

 on the chart at many places down to 45 fathoms, it is only here 

 and there in the shallower parts that patches of true coral-reef 

 occur, most of the coral indicated, and especially in the deeper parts, 

 being isolated and not reef-building species *. The water increases 

 gradually, though irregularly, to 35 or 40 fathoms, and there is 

 then a steep slope down to 60 fathoms, with a bottom of coarse 

 sand. The submarine plateau is therefore continued, but it would 

 seem as if the top of the slope were here at a greater depth than 

 farther east, being at about 35 instead- of 25 fathoms, and con- 

 se(|uently too deep for the growth of reef-building corals. 



The plateau above mentioned extends northwards for two or 

 three miles, and opposite Spring Garden there is a group of shoals 

 upon it which have interesting relations. An upper terrace (at an 

 average depth of 3 fathoms) reaches out some distance from the 

 shore, but is indented by several bays and channels which are 

 apparently connected with the submarine outlets of subterranean 

 freshwater streams, for in several places water can be seen bubbling 

 up through the sand at the bottom. From this coral plateau 

 several small reefs, known as the Pelican Shoals, rise to within a 

 fathom of the surface ; outside it there is a channel with depths of 

 10 to 14 fathoms, and beyond this two isolated reefs which rise to 

 within 7 or 8 fathoms, and in some places even less. Beyond these 

 the water deepens rapidly to 25 fathoms, and the bottom is coarse 

 sand (see fig. 5, p. 205). The existence of these channels and the 

 growth of the reefs seem to be due to the distribution of the sand 

 by the currents from the submarine springs ; the arrangement, in 

 fact, may be explained on the supposition that when reef-corals are 

 prevented from spreading laterally by the encroachment of sand 

 they grow vertically and build up either bosses or wall-like ridges, 

 according to the shape of the area which is not invaded by sand. 

 Xorth of this locality there is a change in the submarine profile ; 

 the extent of shallow water is much less, the two terraces limited 

 by the three- and the eight- or nine-fathom lines are well-marked, 

 but narrow, and there are steep slopes from 10 to 40 or 50 fathoms. 

 These conditions continue along the greater part of the western 

 coast, and are evidently due to the steep inclination of the original 

 landward slope. 



The only notable interruption of this conformation is opposite 

 Holetown, where there are two deep inlets in the eight-fathom 



* For this information we are indebted to Gr. F. Franks, Esq., M.A., F.G.S., 

 of the Harrison College, Barbados. 



p2 



