of GIBRALTAR, 197 



Upon the eaft fide of the mountain is found another of thefe 

 banks, of confiderable extent, and, as I mentioned before, rifing 

 from the Mediterranean in a rapid acclivity, and reaching to 

 one- third, of its entire elevation. This bank is compofed of fmall 

 particles of cryftallized quartz, of teftaceous bodies rounded by 

 attrition, and of a few minute particles of the calcareous rock ; 

 the whole has a whitifh grey colour. The rain-water, which 

 falls from the bare mountain rock above the fand, brings along 

 with it calcareous matter, which is depofited. upon the bank, 

 and combines its furface into a cruft, which in fome places is 

 fo much indurated as to bear the preflure of the foot. 



In other parts of the mountain, where this fand is furround- 

 ed by the calcareous rock, and covered in and prote(5led from, 

 the adlion of the air, and corrofion of the fea-falts, it is found 

 in a perfedl indurated (late, combined by flalaflitical fpar, and 

 forming a minute breccia. A quarry of this arenaceous ftone 

 has been opened upon the fouth-eaft quarter of the mountain,, 

 and is made ufe of, with great propriety, to line the embrafures 

 of fome of the new works belonging to the garrifon. Its inap- 

 titude to fly off in fplinters, when ftruck by a ball, gives, in. 

 fuch fituations, additional fafety to the defenders of the place. 



The weftern fide of the mountain's bafe, around Rofia Bay, 

 and the new Mole, is a rock compofed of an aggregate of fmall- 

 fragments of every fofTil that has been here defcribed, with the 

 addition of two different fpecies of marble that are probably ad- 

 ventitious, as their native beds have not been found in the 

 mountain. The one of thofe is black, and the other of an olive 

 green colour. The whole of this mixture produces a moft beau- 

 tiful breccia, and is firmly combined by a calcareous cement of 

 a yellow, verging towards an orange colour. It is fufceptible of 

 a high polifh, except where fragments of the argillaceous flrata 

 occur : Thefe can be eafily fmoothed down, but cannot be 

 brought to a perfedl polifh. The fragments in this breccia are 



angular^. 



