Mr. De la Beche on the Geology of Jamaica. 151 



by the name of St. George's Gap, a rock is seen partly composed of a kind of 

 marly argillaceous slate^, apparently grauwacke, some of its beds resembling 

 those found on the Agua Alta. These dip to the N.E., and therefore would 

 appear to underlie the limestones of the Buff Bay River; they however seem 

 mixed near the summit of the mountain with red-sandstone and red conglo- 

 merate beds^ resembling those found on the BufF Bay River, to the south of 

 Charles Town Maroon Town, and noticed above as passing into grauwacke : 

 these red beds are the more remarkable as they also very much resemble those 

 found on the summit and southern face of the same mountain, which would 

 appear to constitute parts of a newer formation than the grauwacke. The 

 beds of red-sandstone and conglomerate associated with the grauwacke on the 

 northern side of St. George's Gap dip at a considerable angle to the N.E., 

 while the beds on the summit and southern face of the mountain dip at a great 

 angle to the S.W. : the dips become so suddenly altered that it is somewhat 

 difficult to suppose them arched. 



Submedial or Transition Limestone. 



The Buff Bay River affords a fine section of grayish blue compact limestone, 

 traversed by more or less numerous veins of calcareous spar, and altogether 

 resembling, in mineralogical structure, the common submedial or transition 

 limestones of Europe. I did not discover organic remains in it, such as belong 

 to similar rocks in other parts of the world, — in fact I was not fortunate enough 

 to meet with any ; but occurring as it does among the rocks mentioned above, 

 and being so completely associated with them, there can be little doubt that 

 they belong to the same epoch of formation : and, if the sandstones, conglome- 

 rates, and argillaceous slates mentioned above were formed at the same time 

 with the grauwacke rocks of Europe, the limestones under consideration must 

 be submedial or transition limestones. 



The upper beds of these limestones are much mixed with sandstones ; the 

 latter however gradually disappear, and the former become alone associated 

 with a marly slate containing calcareous matter. These strata are frequently 

 much contorted and twisted, of which the river sections afford many fine ex- 

 amples; no great dependence can therefore be placed on dips : it may, never- 

 theless, be as well to state that at Belcarres, the strata dip to the N. W., having 

 previously dipped to the N.N.E. The marly slate becomes very abundant as 

 we approach the ascent of the mountain to St. George's Gap, some short di- 

 stance up which these strata are continued. 



It should be remarked that a kind of coal is stated to have been found 

 among the Belcarres strata. I had no opportunity of examining a specimen 



VOL. II, — SECOND SERIES. X 



