ON THE GKOLOUrOK IJAKIJADOS. 



217 



sands and muds enclosing a few shells ; below it were Scotland 

 rocks, dipping at an angle of 25"". 



In a cave recently discovered by the Water-Sapply Company be- 

 tween Colo's Cave and Harrison's Cave the solid coral-rock rests on 

 a soft deposit consisting of coral-sand and partly of siliceous Radio- 

 larian earth washed out of the Oceanic Series, and containing many 

 broken and waterworn fragments of corals. This basal deposit is 

 evidently a submarine sandbank formed outside a higher coral-reef; 

 when renewed upheaval brought this sandbank within the limits 

 of coral-growth it became the basis of the next reef. 



Caves are not convenient places for geological observations, but 

 there are several localities in the eastern part of the island where the 

 base of a coral-reef is well exposed and easily accessible, and in one 

 of these we find an instructive section showing the complete discord- 

 ance of the three rock-groups of which Barbados consists. It occurs 

 in a small valley opening into Sheetes Bay on the coast, about half 

 a mile south of Bell Point. To the north of the bay the coral-rock 

 makes up the whole of the cliff, but gradually thins off southward 

 against a bank of Radiol arian earth ; this rests on Scotland clays 

 and sandstones out of which the bay has been eroded. In the 

 steep bank on the south-east side of the bay the rocks exhibit the 

 relations shown in fig. 7. The surface of the older rocks is a slope 



Fig. 7. — Section near Sheetes Bay. 



A. Scotland sandstones. 



B. Oceanic beds. 



C. Ooral-rock. 



facing eastward, and against this the coral-reef has been built ; itS' 

 base is a conglomerate consisting of ironstone nodules derived from 

 the Scotland clays and cemented by calcareous matter into a hard 

 rock which passes up into a calcareous sandstone from 6 to 8 feet 

 thick. The higher beds consist of rock with corals and coral- 

 debris, and then thin off inland against the slope of the siliceous 

 earths. 



At Culpepper Island there is coral-rock resting on a bed of re- 

 deposited Radiolarian earth containing small corals and land-shells, 

 and about 8 feet thick ; this lies on the Scotland strata, which here 

 occupy the coast-line. 



The reefs thus exposed on the coast are of course very recent 

 coral-rock, but the base of an older reef is exposed beneath St. 

 Mark's Church, where the surface is 258 feet above the sea. The 

 coral plateau is hero cut back into an escarpment which faces west,, 



