194 MINERJLOGICJL DESCRIPTION 



The variety of form, which this matter takes in its different 

 fituations and direcftions, renders this fubterraneons fcenery 

 ftrikingly grotefque, and in fome places beautifully pidlurefque. 

 The flaladlites of thefe caves, when near the furface of the 

 mountain, are of a brownifh yellow colour ; but, as we defcend- 

 ed towards the lower caves, we found them begin to lofe their 

 darknefs of colour, which by degrees fhaded off to a whitifli 

 yellow. I ..jj -^i^/jj jL J - .: 



The only inhabitants of thefe caves are bats, fome of which 

 are of a largg^fize. The foil, in general, upon the moun- 

 tain of Gibraltar, is but thinly fown ; and in many parts that 

 thin covering has been waflied off by the heavy autumnal 

 rains which have left the fuperficies of the rock, for a confidcr- 

 able extent, bare and open to infpedion. In thofe (ituations, 

 an obferving eye may trace the fcffecls of the flow, but conflant, 

 decompofition of the rock, caufed by its expofure to the air, and 

 the corrofion of fea-falts, which, in the heavy gales of eafterly 

 winds, are depofited with the fpra^ on every part of the moun- 

 tain. Thofe uncovered parts of the mountain rock alfo expofe to 

 the eye a phcenomenon worthy of, fome attention, as ititends clear-; 

 ly to demonftrate, that, however high the. furface of this rock 

 may now be elevated above the ley.eli of the fea, it has once 

 been the bed of agitated waters. This phgenomenon is to be 

 obferved in many partS'of the rock, .and is conftantly found in: 

 the beds.'^f itprrents.. . : Jt confifts of pot-like holes,, cif .varioTis 

 fizes, hollowed out of the folid rock, and formed apparently bv 

 the attrition of gravel or pebbles, fet in Action by the rapidity 

 of rivers, or currents in the fea. One of thofe, which had been 

 recently laid open, I exaiminedi with attention. I foundi: it: to- 

 be five feet deep, and three- feet id diapeterr; the edge dfvits 

 mouth rounded off as if by art, and its fides and bottom retain^v 

 ing a confiderable degree^ o£ ;polifh. ■ i Erom its mouth,, for three 

 and a half feet down, it was filled; ,with^ a rcd' argillaceous earth;: 

 ^,,v r, A .Vi .thinly 



