574 Correspondence — Mr. A. R. Hunt. 



2. " On a New Cave on the Eastern Side of Gibraltar." By 

 Henry Dyke Acland, Esq., F.G.S. 



This cave, discovered in 1902, is situated a short distance south 

 of the eastern end of the tunnel, which pierces the Rock from the 

 Dockyard on the western side to ' Monkeys' Quarry ' on the eastern. 

 It was opened by blasting operations ; and from the opening thus 

 made, 88 feet above sea-level, the floor falls to the west. The main 

 hall is about 70 feet high and 45 feet wide, and has a smooth 

 stalagmite floor resting on breccia and a stalactitic roof covering 

 the limestone of the Eock. Its floor falls to a point 19 feet above 

 sea-level. The lower gallery descends at its far end to little, if 

 anything, short of sea-level. Its floor consists of stalagmite resting 

 on fine calcareous sand ; this on coarse sand, followed by rubbly 

 and calcareous grit, which in time rests on the rock-floor of the 

 •cave at a depth of 15 feet. In the calcareous grit are numerous 

 well-rounded stones, some pierced by pholades. At a depth of 

 13 feet were echinids and barnacles. Two other galleries were 

 explored, and in these, as in the lower gallery, the walls are pitted 

 to a height of 28 feet above sea-level. The author concludes that 

 the cave existed at first as a fissure, to which the sea later obtained 

 access through a large entrance for a long period ; and during this 

 period the Eock was elevated some 42 feet. The cave was closed, 

 to the sea at a period geologically recent; and the breccia and 

 sand-slopes at this point on the eastern side of the Eock, which are 

 150 feet wide and reach to a height of 200-300 feet above sea-level, 

 date from a still more recent period. 



C0I^I^:ESI='03^lD:B35^c:H]. 



A FINAL WORD ON FLUID INCLUSIONS. 



Sib, — I am very sincerely obliged to General McMahon for his 

 full reply to my paper on granite. I can assure him that he is 

 mistaken in supposing my motives to be sinister. 



Since the late W. Pengelly, F.E.S., in 1862, read his paper 

 "On the Age of the Dartmoor Granites" (mark the plural), the 

 granite problem has greatly interested local geologists, who, for 

 forty-one years, have fought over the question with equal keenness 

 and good temper. 



General McMahon now writes, " My critic's conclusion is irre- 

 concilable with the facts stated in my Belfast address, hence 

 possibly his anxiety to discredit my facts under cover of an attack 

 on the views expressed by me " ! Now I never to my knowledge 

 bolstered a theoi-y, or sought to discredit a fact ; and, so far from 

 wishing to discredit General McMahon's facts, I should be as pleased 

 to see his theory confirmed as anyone else's, and certainly as well 

 as my own. "With regard to my being called upon to defend my 

 position by proving Dr. Sorby's views erroneous, I think Genera 

 McMahon must have had in his mind Dr. Sorby's paper of 1858, 

 My authority as to the significance of deposited chlorides is chiefly 



