Vol. 60.] NEW CAVE AT GIBRALTAR. 36 



inward from the entrance. The middle gallery enables us to see 

 that the old entrance is blocked up by breccia. That its position is 

 not due to the force of the waves is evident from its being breccia, 

 and not conglomerate. Sir Andrew llamsay & Prof. James Geikie 

 in their paper l discuss at considerable length the origin of the 

 breccias of Gibraltar, and they consider that ' they belong to two 

 distinct stages.' although in the map which accompanies their paper 

 the same sign is used for both. The discovery of the echinids in the 

 lower gallery tends to disprove that the later breccias, at any rate. 

 owe their origin to ■ cold climatic conditions." ' When the tunnel was 

 made through the Rock, from the west near the Moorish castle, to the 

 catchment-area above Catalan Bay, a narrow fissure was discovered 

 that extended vertically from the outer air to an unknown depth. 

 If this went so far down as to reach the sea-level and was then 

 undermined, it would cause an enormous fall of rock, and if that 

 happened at the mouth of a cave, no doubt some of it would fail 

 inside and form a sloping floor such as there is in this cave. In 

 course of time the rubble would be consolidated into breccia. 



The conclusions, therefore, that may be arrived at from the 

 evidence furnished by this cave are : — 



1. That it existed as a fissure-cave before it was subjected to the 

 action of the sea. 



2. That it had a large entrance open to the sea for a long period. 

 '.'). That during that time the Rock was elevated some 42 feet. 



4. That it was closed to the sea at a recent geological period. 



5. That the breccia and sand-slopes at this point on the eastern 

 side of the Rock, which are 150 feet wide and reach to a height of 

 200 or 300 feet above sea-level, date from a still more recent epoch. 



In conclusion, I wish to express my obligations to the Admiral 

 Superintendent for allowing me the opportunity of examining the 

 cave : to Mr. A. Scott, Chief Civil Engineer, Messrs. L. T. Stoddard 

 & A. K. Peaty, Assistant Civil Engineers, and Mr. R. Taylor, 

 contractor's agent : to Mr. R. I. Tngles, one of his superintendents ; 

 and to the Hon. F. AY. D. Smith. M.P., for much courtesy and 

 assistance in the way of plans, photographs, etc. 



EXPLANATION OF PLATE VI. 



Fitr. 1. Longitudinal section of the cave at Monkey's Quarry. Gibraltar, on 

 the scale of 40 feet to the inch. 

 2. Plan of the cave at Monkey's Quarry. Gibraltar, on the scale o|'4<t feet 



to the inch. 

 o. Transverse section of the same at XY. 



Discussion. 



Dr. A. Smith Woodward expressed satisfaction that renewed 



1 Quart. Journ. Geol. Soc. vol. xxsiv 187§ p. 515. 

 - .Ibid. p. 530. 



d2 



