522 A. C. RAMSAY AND J. GEIKIE Otf 



this plain is more or less sandy and stony ; immediately under- 

 neath, however, we come npon sands which are generally pure and 

 sharp, and contain numerous sea-shells of existing Mediterranean 

 species. In "Well No. 1, sunk by the Sanitary Commissioners of 

 Gibraltar just within the British lines, a stratum of clay 2 feet thick 

 was reached at a depth of 30 feet, underneath which come beds of 

 sand which have not been sunk through. The average level of the 

 surface is not more than 10 feet above the sea. 



Mr. Smith mentions the occurrence of Balani, shells of Pholades, 

 and clusters of mussels in a crevice exposed in a quarry at the 

 North Front, at a height of 24 feet above the present littoral zone. 

 We found no trace of this crevice, and the deposit has probably been 

 removed during the quarrying operations which are constantly being 

 carried on at that place. The same writer also refers to the occur- 

 rence of two raised beaches, one " at the height of 50 feet, and 

 another 20 feet higher," as having been disclosed during the 

 scarping of the ancient sea- cliff at Europa Point. From these 

 deposits he collected upwards of 100 species of recent sea-shells ; 

 but the whole of the rock below the fortifications at Europa Point 

 having been scarped and otherwise interfered with, the deposits 

 mentioned by Mr. Smith are now no longer visible. 



The next well-marked old sea-level is that of Europa Flats (see 

 Section VII.), a wide plateau of bare limestone rock, forming the ex- 

 treme southern portion of the promontory. From west to east it 

 measures about 1650 feet, and 800 feet or thereabouts from the 

 batteries to the base of the Windmill-Hill cliff. Its average eleva- 

 tion is about 115 feet over the present sea-level, but it slopes up 

 from 90 feet or so to 150 feet or thereabout. The surface has been 

 " dressed," so as to make it more even ; but here and there, in hollows 

 of the honeycombed limestone, we noticed small patches of hardened 

 sand, made up of triturated and comminuted fragments of limestone 

 and shells*. Mr. Smith detected in one patch in this place a valve 

 of Pecten maocimus. Leaving Europa Flats by the main road, we 

 are conducted past the Governor's Cottage towards the No. 3 Europa 

 Advance Battery along a terrace or platform of limestone which is 

 backed by the cliffs of Windmill-Hill Flats. The surface of this 

 terrace is buried to a considerable depth under limestone- agglomerate, 

 but there can be no doubt that it is only a continuation of the 

 Europa plateau. Above No. 3 Europa Advance Battery, on Mon- 

 key's-Cave Road, there is a quarry opened in calcareous sandstone, 

 which is evidently a littoral or shallow-water deposit that rests 

 upon the limestone terrace or shelf at present under consideration. 

 The sandstone is usually greyish yellow or grey, but here and there 



* When we remember that a very strong current sweeps past Europa Point, 

 we need not wonder that so few traces of marine deposits should be found upon 

 the Europa plateau ; for when this plateau formed a part of the sea-bottom, 

 there can be little doubt that it would be traversed by the same rapidly flowing 

 water, and hence no great accumulation of detritus could take place. The sand- 

 beds of the promontory occur only along such parts of the coast as were and 

 still are free from the action of this strong current. 



