of G I B RJ L r A R, 19* 



beds of which are to be examined in a face of 1350 feet of per- 

 pendicular height, which it prefents to Spain in a conical form. 

 Thefe beds, or ftrata, are of various thicknefs, from 20 to up- 

 wards of 40 feet, dipping in a dire(5lion from eafl to weft, near- 

 ly at an angle of t,^ degrees. In fome parts of the folid mafs of 

 this rock, I have found teftaceous bodies entirely tranfmuted 

 into the conftituent matter of the rock, and their interior hollows 

 filled up with calcareous fpar ; but thefe do not occur often in 

 its compofition, and its beds are not feparated by any interme- 

 diate ftrata. 



In all parts of the globe, where this fpecies of rock conftitutes 

 large diftri(5ls, it is found to be cavernous. The caves of Gi- 

 braltar are many, and fome of them of great extent. That 

 which moft deferves attention and examination is called St Mi- 

 chael's Cave, which is fituated upon the fouthern part of the 

 mountain, almoft equally diftant from the Signal Tower and 

 the Sugar Loaf. Its entrance is 1000 feet above the level of the 

 fea : This entrance is formed by a rapid flope of earth, which 

 has fallen into it at various periods, and which leads to a fpa- 

 cious hall, incrufted with fpar, and apparently fupported in the 

 centre by a large mafly ftala(5litical pillar. To this fucceeds a 

 long feries of caves of difficult accefs. The paflages from the 

 one to the other of thefe are over precipices, which can only be 

 palTed by the alTiftance of ropes and fcaling ladders. I have, 

 myfelf, palTed over many of thefe to the depth of 300 feet from 

 the upper cave ; but at that depth the fmoke of our torches be- 

 came fo difagreeable, that we were obliged to give up our pur- 

 fuit, and leave caves ftill under us unexamined. In thefe ca- 

 vernous recefTes, the formation and procefs of ftala(5lites is to be 

 traced, from the flimfy quilt-like cone, fufpended from the roofj 

 to the robuft trunk of a pillar, three feet in diameter, which 

 rifes from the floor, and feems intended by nature to fupport 

 the roof from which it originated. 



Vol. IV. A a The 



