186 Mr. De la Beche on the Geology of Jamaica. 



(which is of some thickness) formerly extended^ it would be difficult to say ; 

 hundreds of people having visited this cavern^ as their names^ scrawled upon 

 the wall with charcoal^ testify^ and the floor in consequence, as may be rea- 

 sonably inferred, not presenting the same appearance as when the cavern was 

 first entered. The cave is situated on the side of a hill, within a short distance 

 from the sea ; but it is sufficiently elevated to prevent the possibility of the 

 clay having been derived from the sea at its present level*. 



Volcanic Rocks. 



In that part of Jamaica which 1 examined, I observed rocks of this cha- 

 racter only at the Black Hill, which is situated between Lennox, Low Layton, 

 and the sea (St. George's). This hill, when viewed from the neighbourhood 

 of Buif Bay, has a somewhat conical appearance, and rises above the low hills 

 that extend towards Savannah Point : the hill, however, when approached is 

 seen to be no cone, notwithstanding its effect at a distance. 



The rock, of which the Black Hill is principally composed, is grayish 

 brown and hard, gives out an earthy smell when breathed on, and may in 

 general terms be described as a volcanic amygdaloid, the cells, with which it 



admitted the light of day ; and the rubbish formed a rough ascent and descent, occupying about 

 60 paces of the cavern's length. We then entered a chamber 14 paces long, which is succeeded 

 by a low passage, where we could not stand upright, 21 paces in length. After passing (his low 

 place, we found ourselves in a chamber 14 paces long, and we then entered a low place where 

 the bed of limestone that formed the roof gradually approached the clay floor and prevented 

 further progress. 



Near this cavern is another, from which the people on Swansea estate obtain their supply of 

 water, which remains at a greater or less depth in it according to the seasons. Sometimes, when 

 heavy rains have fallen in certain parts of the neighbourhood, with which it must have communi. 

 cation, it rushes out of the cavern with great noise and impetuosity into a gully, but is soon 

 swallowed up among the sink-holes. 



* The entrance into Portland Cave is easy, and, from being low, not very striking ; but when 

 we had entered a short distance a fine chamber presented itself, ornamented with several very 

 beautiful stalactitic columns. We then proceeded to another branch of considerably larger di- 

 mensions than the first. This portion is extremely beautiful, the stalactites are well arranged for 

 effect, and the whole had a fine appearance when the negroes with torches were proj)erly distri- 

 buted among the columns, many of which are of large dimensions, and beautifully crysfallized on 

 the surface. After examining this chamber, which is of considerable length, we retraced our steps 

 for some distance, and then branched off through passages, in two or three places rather low, 

 into a lofty and winding chamber of some length, which did not however possess the beauty of 

 the first : at the end we crawled through a low passage upon our hands and knees, and entered 

 a small chamber that communicated with the surface. We found the heat in this cavern very 

 great, probably arising from its being near the surface. 



