248 RASAV. GEOLOGY. 



The next rock which follows this and immediately pre- 

 cedes the red sandstone near Brochel Castle, is a gray- 

 wacke schist, forming a thin set of beds in very regular 

 order and position, and easily examined on the sea shore 

 throughout their whole extent. Higher in the hill, they 

 are found in contact with the gneiss, but in other places 

 they appear to be wanting ; or, if present, the quantity 

 is so small that it is easily overlooked in a tract so covered 

 with heath and bog. 



The substance here described is a fine graywacke slate, 

 the lamina? being separated by mica ; and it is remarkable 

 for the number and regularity of the square and rhom- 

 boidal fragments into which it breaks. Among the beds 

 are found two or thre containing small and large frag- 

 ments of gneiss and quartz, cemented by the fine slate 

 and graduating into it. This slaty conglomerate is irre- 

 gularly disposed in alternation with the fine graywacke, 

 and is separated by a wide interval of this substance from 

 the conglomerate formerly described; with which it appears 

 to have no connexion in structure more than in position. 

 It may perhaps by some geologists be called a coarse 

 graywacke ; but it differs in general character so widely 

 from this substance, that I have preferred the use of 

 the term conglomerate, for the purpose of avoiding the 

 indistinctness and confusion that follow so lax a use 

 of the former name. It is in itself a sufficient indication 

 of the mechanical nature of the process by which the 

 whole of the series connected with it was formed. 



The position of this mass of graywacke, intermediate 

 between the first conglomerate of the sandstone series 

 and the great body of that rock, would seem to indicate 

 some anomaly peculiar to this spot; but it will here- 

 after be seen in examining Sky, that it can only be viewed 

 as an alternation of the graywacke and sandstone, innu- 

 merable examples of which occur throughout the whole 

 country. 



This rock is followed by the mass of red sandstone 



