41 



PROCEEDINGS, 



ETC. 



POSTPONED PAPERS. 



On the Geology (/Gibraltar. By James Smith, Esq., of 

 Jordan Hill, F.G.S.* 



[Read Nov. 20, 1844.] 



The continent of Europe is terminated on the south and that of 

 Africa on the north by a secondary formation of considerable ex- 

 tent, which is cut into two by the Straits of Gibraltar. The pre- 

 vailing rock on both sides is siliceous sandstone, generally of a 

 yellowish brown colour, which is associated with limestone and shale 

 in different states of induration, and also with subordinate beds of 

 chert and coal. Judging from external character I should pronounce 

 it to belong to the true coal-measures, but the indications furnished 

 by organic remains point rather to the Jurassic group. The evidence 

 however is by no means conclusive ; fossils are of such rare occur- 

 rence and in such an imperfect state, that no certain inference can, 

 in the present state of our knowledge of its organic remains, be 

 drawn from them. The Gibraltar limestone contains casts of marine 

 shells, chiefly Terebratulse, one of which appears to be the T. fim- 

 bria and the other the T, concinna of the ' Mineral Conchology,' both 

 belonging to the lower oolite. A coal-pit has lately been opened 

 about four miles to the north of Gibraltar, but hitherto with no other 

 success than the discovery of a bed of arenaceous shale, with thin 

 flakes of highly crystalline coal. The late Mr. Drummond Hay, 

 the British consul at Tangier, informed me that there are also indi- 

 cations of coal on the African side of the Straits. 



The hills round the Bay of Gibraltar rise to an elevation of be- 

 tween 2000 and 3000 feet, and at their base there is a series of low 

 swelling hills of tertiary limestone, which, as I have elsewhere shown, 

 belong to the great miocene formation of the south of Euro})e !• 



The mountain or rock of Gibraltar, as it is usually called, forms 

 an oblong peninsula, extending two miles and a half from north to 



* See Quaiterly Journal of the Geological Society, vol. i. p. 298. 

 t Ibid, vol. i. p. 235. 



