28 W. GTJNN AND C. T. CLOTJGKK ON THE 



Sketch Map showing the position of Silurian Beds in Teesdale. 





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It is by this great disturbance that the lowest beds which are seen 

 in the Dale are brought up. These lowest beds are to be found near 

 the old Pencil Mill at Cronkley, and they are exposed along the river- 

 side for a length of nearly 700 yards. Probably, if the thick riggs of 

 Boulder-clay which cover up so much of the low ground about here 

 could be removed, the beds would be seen to occupy a much larger 

 area. We have indicated in the above sketch map where these beds 

 are to be seen, and the probable line of the Burtreeford Dyke. 



These Pencil-mill beds consist of soft shales which were formerly 

 worked up into slate-pencils at the Old Mill. Their general tint is a 

 grey or greenish grey ; but sometimes they are of a more decided light 

 yellowish green,and sometimes of a purplish red colour. They are very 

 homogeneous in character, fine in texture, and with apparently no 

 definite bands of a hard or gritty character, such as would enable 

 one to make out any distinct bedding. The shale is much laminated 

 in places, and crossed by several sets of divisional planes ; but the 



