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



Micaceous Slate and Hornstone. — The latter interstratified in thin beds 

 with argillaceous slate of a micaceous lustre^ is found on the ascent of the Blue 

 Mountains between Green Valley and Sheldon. The hornstone is striped, 

 and sometimes splits into a slate resembling flinty slate. These strata dip to 

 the N.E. at angles varying from 60° to 70°, apparently beneath the mass of 

 rocks which are crowned by the Blue Mountain Peaks. 



A light-coloured sandstone is met with between Charlottenburg and Isling- 

 ton in the parish of St. Mary, which differs from the grauwacke of the coun- 

 try, and indeed from any grauwacke I have ever seen ; yet as it occurs among 

 this submedial district, and does not appear connected with any secondary 

 rock, its place would seem to be among the class of rocks under consideration : 

 and I may also observe that there are some other strata in the same parish, 

 particularly slaty brown marls with thin seams of white occasionally associated 

 with them, which it would be difficult to separate from the grauwacke of Ja- 

 maica, though they differ from the grauwacke of Europe. These strata are 

 observable in one or two places between Charlottenburg and Islington, as also 

 on the mountain between Albion estate near Port Maria, and Eden near Ora 

 Cabessa. 



In the whole of this submedial or transition country I was not fortunate 

 enough to meet with any fossil organic remains, except the vegetable impres- 

 sions of the sandstone in the mountain between Port Maria and Ora Cabessa. 

 I may therefore be asked why I have named the limestone associated with 

 these rocks, transition or submedial lim.estone .? — I can only reply, that it mi- 

 neralogically resembles the transition limestones that I have seen in various 

 parts of Europe and Great Britain, and that it occurs with a sandstone and 

 conglomerate very much resembling grauwacke, with argillaceous slate, sy- 

 enites, greenstones, &c., in fact associated as submedial limestones often are 

 in other parts of the world. 



It should be remarked of this group of rocks, that the most general dip of 

 the mass composing the Blue Mountain Range is to N.E. and E.N.E., most 

 commonly at a considerable angle, which dip is continued into the northern 

 part of St. Mary's parish near Carlton Wood House, but further north in the 

 same parish the dip becomes reversed, and is to the S.W. ; it continues S. or 

 S.E. along the line of junction with the red-sandstone and conglomerate to 

 the Agua Alta, so that the strata would seem to be arched in some parts of 

 St. Mary's : the rocks however on the northern face of Catherine's Peak dip 

 to the N.E. 

 The submedial strata of the eastern part of the island have a tendency to 



