View in the Longmynd Hills, looking E.S.E.,from a drawing by Mr. T. Webster, F.G.S. 1 



CHAPTER XXI. 



CAMBRIAN SYSTEM. 



PART OF THE UPPER GROUP. 



Mineral Axis of Shropshire. — Cambrian and associated Trap Rocks in the Hills 

 of Longmynd, Ratlinghope, Linley, Pontesford, Lyth, and Haughmond. (PI. 31. 

 f. 4. PL 32. figs. 1, 2 and 4. PL 33. f. 1.) 



Having described the Silurian formations in the district selected as a type, and also 

 the associated rocks of volcanic origin, I now enter upon the consideration of the older 

 sedimentary deposits and the intrusive rocks by which they are intersected. 



From their great development in Wales, where throughout a course of one hundred 

 and fifty miles, they either flank unconformably, or rise out regularly from beneath the 

 Silurian strata, Professor Sedgwick has assigned to these rocks the name of Cambrian. 

 This vast system (of infinitely greater thickness than any other in the geological series) 

 is intended by that author to embrace all the older slaty rocks, and has been divided 



1 The above vignette and some other illustrations of this work, including the wood-cuts 24, 26 and 28, are 

 taken from a series of characteristic sketches of this neighbourhood by that able geologist and accomplished 

 artist Mr. Thomas Webster, so long Secretary of the Geological Society of London. The drawings were made 

 in the early days of geology in England, and were intended to illustrate a work on Shropshire (never completed) 

 by Mr. A. Aikin, F.R.S., who liberally placed them at my disposal. 



2 i 2 



