Vol. 54.] ON THE GLOBIftEBINA-MAELS, ETC., OP BARBADOS. 541 



It was felt, nevertheless, that the locality required further investi- 

 gation, and the present paper records the results of subsequent 

 explorations of Bissex Hill. These were communicated from time 

 to time to Mr. Jukes-Browne, and the conclusions to which they 

 seemed to point were mentioned in a letter written by him, and 

 read at a meeting of the Geological Society on Feb. 20th, 1895.^ 



The principal points thus ascertained are as follows : — 



(1) That there is no break in the succession of the Globic/erina- 

 marls and coral-limestone. These marls pass upwards conformably, 

 through a basal reef-rock without corals, into the coral-rock which 

 caps the island. Included fragments of the chalk, of the radiolarian 

 earth, and of clay containing radiolaria occur in the lower beds as 

 well as in the upper. Where these inclusions are largest and most 

 plentiful, they are in the form of rounded, or more often flatly-ovate, 

 pebbles, and are thus easily distinguished from the angular blocks 

 and fragments of Globigerina-lim.esto'D.e, which in places occur in the 

 marls and themselves contain inclusions of the Oceanic rocks. 



(2) The Globig erina- jnarls lie unconformably on the Oceanic 

 Series, in some places resting on the siliceous radiolarian earths, in 

 others on the upper calcareous earths or chalks. 



(3) The central and highest portion of the hill is a faulted tract, 

 the mass of the Glohiger in a-marls being troughed down between 

 two main fault-planes and slightly displaced by another fault. 



(4) The same series of GIobigerina-msLrls and basal reef-rocks 

 has also been found in a shaft and a natural cave at Bowmanston, 

 an estate about 4^ miles south-east of Bissex Hill. 



II. The Oeographic and Tectonic Structure oe Bissex Hill. 



It is on Bissex Hill that we have found the clearest evidence of 

 the unconformity of the Globigerma-msiTls with the Oceanic Series 

 and their conformity with the coral-rocks. 



Bissex Hill is a very irregular tract of high ground on the north- 

 eastern side of the island of Barbados. From its highest point, 

 which is 966 feet above sea-level, it sends out spurs towards 

 the east and the north-east, divided by deep valleys which slope 

 steeply down to the coast. On the north a ridge extends to 

 the hill known as Chalky Mount, the northern slopes of which 

 sink almost precipitously to the Valley of St. Andrews. On the 

 south-east and south it slopes somewhat steeply into the valley 

 of a little brook called Joe's River. Another little brook, known 

 as Tar Hole Gully River, divides a spur, running nearly due east 

 and capped by two outliers of radiolarian earth, from two con- 

 tiguous spurs running a little north of east, along and partly across 

 which a fault-line can be traced. On the west it sinks into 

 another deep valley known as Dark Hole, which drains northward. 

 Between the valley of Dark Hole and the western part of the Joe's 

 River valley is a high ridge running south-westward, which, like 

 the neck of an isthmus, unites Bissex Hill to the central highlands 



' See Quart. Journ. Geol. Soc. vol. li, p. 311. 



