Stachpole Rock, from a drawing by Mrs. Murchison. 



CHAPTER XXIX. 



GEOLOGICAL STRUCTURE OF PEMBROKESHIRE. 



Part I. Introduction. — Coal or Culm Measures. — Millstone Grit. — Carboni- 

 ferous Limestone. — Old Red Sandstone. (PI. 35. figs. 1, 2, 3, 4, 6, 6, 7, 

 8 and 9.) 



Having traced the Silurian Rocks to the western horders of Caermarthenshire, I 

 propose to show the manner in which they are prolonged to the coast cliffs of Pem- 

 brokeshire. In the mean time, however, as this county contains all the formations from 

 the coal measures to the Cambrian Rocks inclusive, the present chapter is offered as a 

 synopsis of much that has been diffused through the previous pages, concerning some 

 of the overlying deposits, (p. 79 to 174). 



Unlike the greater portion of the region examined, Pembrokeshire has received some 

 attention from geologists. The mineralogy of a part of the northern district was de- 

 scribed by Dr. Kidd 1 , and the geological structure of the southern was laid down, in the 

 year 1820, upon the Ordnance Map by Mr. De la Beche, and published with a memoir 

 in the Geological Transactions 3 . Although the general relations of the carboniferous 

 system (with one exception) were then pointed out, no attempt was made to establish 

 a succession of strata below the Old Red Sandstone. The whole northern district was 

 marked as " grauwacke," a name which, until recently, comprehended every rock 

 from the roofing slates to the beds immediately beneath the Old Red Sandstone ; and 



1 Geol. Trans., vol. ii. p. 79. (Old Series.) 2 Geol. Trans., vol. ii. p. 1. (New Series.) 



