CAMBRIAN. 77 



CAMBRIAN. 



LAKE DISTRICT, ETC. 



While we are chiefly indebted to Sedgwick^ for the earhest 

 interpretations of the structure of the Lake District, the older 

 rocks which enter most largely into its composition were in 

 later years studied in great detail by James Clifton Ward,"^ 

 whose enthusiastic and successful labours were unfortunately 

 terminated at an early age. The work on the Geological 

 Survey among the older rocks of the Lake District was per- 

 formed partly by Mr. Ward, and partly by Mr. W. T. Aveline, 

 Prof Hughes, Mr. J. G. Goodchild, and others. The rocks 

 include the following divisions (see p. 50) : — 



/ Ashffill Shales. 



3. Coniston Limestone Series. | Coniston Limestone. 



( Dufton Shales. 

 2. Borrowdale Series. 

 I. Skiddaw Slates. 



They may represent rocks that in Wales range from the 

 period of the Lingula Flag Series to the top of the Bala 

 Series. 



SKIDDAW SLATES. 



The slates of Skiddaw are the oldest rocks in the Lake District. 

 They comprise shales and mudstones, usually much cleaved, and of 

 a dark bluish or black colour, and they contain flaggy beds with 

 veins of quartz. The term Skiddaw Slates was originally used by 

 J. Otley, because the slates rise up in the mountain of Skiddaw. 

 The fine black slates show the cleavage best, while the Rev. J. C. 

 Ward has remarked on the difficulty, and sometimes the impossi- 

 bility, of determining the original bedding. In the series he 

 observed ripple-marked flags, grits, and conglomerate. One band 

 of conglomerate occurs high up in the series, but it did not, in his 



1 See his Geology of the Lake District, in Three Letters addressed to W. 

 Wordsworth, 1843. 



2 Geology of the Northern Part of the Lake District, 1876 ; Q. J. xxxii. 12 ; 

 G. Mag. 1879, p. 50. See also numerous papers by R. Harkness ; Dr. H. A. 

 Nicholson, Geology of Cumberland and Westmorland, 1S68. 



