

ON THE GEOLOGY OF GIBRALTAR. 505 



33. On the Geology of Gibraltar. By A. C. Ramsay, LL.D., 

 F.R.S., and James Geikte, LL.D., F.R.S. (Read March 6, 



1878.) 



[Plate XXIII.] 



Contents. 



Introduction : with list of papers &c. referring to the geology of the Eock. 



Physical description. 



Eocks entering into the formation of the promontory. 



Description of sections across the Eock. 



Notes on adjacent tracts in Spain, and on the African coast opposite. 



Superficial deposits, &c, of Gibraltar : — ■ 



1. Older limestone-agglomerate of Buena Vista, &c. ; origin of agglomerates . 



2. Bone-breccias in caves and fissures. 



3. Eaised beaches, calcareous sandstones, &c. 



4. Alameda sands. 



5. Catalan sands, &c. 



6. Later limestone-agglomerates. 



Probable succession of events during accumulation of superficial deposits. 

 Concluding remarks : cause of the conditions that gave rise to the formation 

 of the great limestone-agglomerates. 



Introduction. 



At the request of the Colonial Office, we visited Gibraltar in the autumn 

 of 1876, for the purpose of inspecting and reporting upon the water- 

 supply to the town and garrison. In order to do adequate justice 

 to this important subject it was found necessary to make a complete 

 geological survey of the Rock, and to lay down the details on a map 

 in the usual way, and also to construct a series of sections on 

 a true longitudinal and vertical scale. The report subsequently 

 furnished by one of us to the Colonial Office contained a general 

 account of the geology of the Rock ; but from this many interesting 

 details were necessarily omitted, as only those features which bore 

 more or less directly on the question of water-supply were treated 

 of at length. It is the object of the present paper to give a more 

 detailed account of our observations, and to point out the very 

 remarkable connexion which seems to us to obtain between certain 

 Pleistocene deposits of Gibraltar and the glacial accumulations of 

 the mountainous regions and more northerly latitudes of Europe. 



The most detailed account of the geology of Gibraltar which has 

 appeared is that given by Mr. J. Smith, of Jordan Hill, in an early 

 volume of this Society's Quarterly Journal. Mr. Smith's paper is of 

 considerable value, more especially as it contains an account of 

 various deposits which are now no longer visible, the operations of 

 quarrying, scarping, and building, which are always going on, 

 having necessarily resulted in the obliteration of some interesting 

 geological evidence. 



