508 A. C. RAMSAY AND J. GEIKIE ON 



brecciiform, an appearance to which further reference will be made 

 in the sequel. 



Fossils appear to be of unfrequent occurrence ; but casts of Rhyn- 

 choneUce and what appeared to be encrinital stems were noted, and 

 here and there on weathered faces the small angular fragments or 

 grit of which the rock is now and again composed seemed to consist 

 in some measure of rolled bits of shells. The only good specimens 

 we obtained were given to us by Mr. E. Roberts, C.E.* ; all of them 

 came from the quarry at the North Eront, and are of one species, 

 somewhat resembling Rhynchonella concinna, which is abundant in 

 England in the Cornbrash and Coral Ragf. 



The limestone is overlain by a series of shales, which are usually 

 of a dull dark greyish-blue colour. Near their junction with the 

 limestone they are often much weathered, and show red, green, 

 purple, yellow, grey, and particoloured shades. In some places 

 they would work up into clay for brick-making purposes. They 

 contain intercalated bands and beds of grit, mudstone, and lime- 

 stone, some of the grits being slightly calcareous. Near the base of 

 the series the intercalated limestones are of considerable thickness 

 and closely resemble the main limestone ; they appear, however, to 

 thicken and thin out very rapidly. Eurther up in the series the 

 calcareous beds are thinner and seem to be more persistent ; at 

 the same time they become more impure, and are rather calcareous 

 grits than limestones. No fossils have been met with in either the 

 shales or the intercalated beds. 



The shales and accompanying beds are best seen upon the beach 

 between Careening Bay and Jones's Battery ; good exposures also 

 occur at many points along the junction between the shales and the 

 underlying limestone, for example, at the Upper-Road Tank, at 

 Windmill-Hill Barracks, and the Devil's Bellows. The same series 

 is also well exposed in the cliffs and banks at Camp Bay, where the 

 dip is apparently under the limestone. 



Before proceeding to notice the limestone -agglomerates and other 

 superficial deposits and accumulations, it will be well to describe the 

 accompanying Sections (figs. 1-7), which will suffice to show the geo- 

 logical structure of the promontory ; and we shall add a few notes 

 on the rocks of the neighbouring Spanish territory and opposite 

 African coast. 



Description of Sections across the Rock. 



Section No. I., from the Mediterranean on the east, crosses the 

 battery on the topmost point of the ridge overlooking the North 



* To Mr. Eoberts we are under great obligations for muck valuable assistance. 

 His position as engineer to the Sanitary Commission has naturally given him 

 the best opportunity of becoming familiar with the geology of the Eock. His 

 minute acquaintance with the ground occupied by the town was of special ser- 

 vice to us, as it enabled us to draw our lines with a precision which would have 

 been otherwise impossible. 



t The specimens were examined by Mr. Etheridge and Mr. Davidson, who 

 could not with certainty determine the species, though both agreed that they 

 were allied to Rhynchonella concinna. 



