GEOLOGY. 19 



to Colsterdale on the east of Great Whernside, or to where the 

 beds of this series fill up the great synclinal depression between 

 Svvaledale and Lunedale, the existence of which has been indi- 

 cated when speaking of the subjacent strata ; or, better still, to 

 the hills which surround the lower part of Wharfedale and 

 Nidderdale, where we shall find it thicker and better developed 

 than it is anywhere within our own proper limits. The various 

 members of the series are very different in different localities, 

 so that it is often a task of great difficulty to decide respecting 

 the identity of the beds, and their proper relation to one 

 another. In the Ilkley and Pateley Bridge tract the series 

 attains in some places a thickness of fully one thousand feet, 

 with strata as under, viz. : — 



Feet. Feet. 



6. Upper grit of the Wharfedale summits 100 to 360 



5. Upper plate and flagstone group with chert and coal, about 200 or 250 



4. Coarse middle or Sandhill grit 30 to 50 



3. Lower plate group, with gritstone, thin limestone, and coal 300 ,, 350 



2. Lower or Ingleborough grit, with plate and coal 100 ,, 300 



I. Chert, limestone and plate beds 12 



The following is the detailed Witton Fell and Colsterdale 



section as observed in the Brown Beck collieries, the gritstone 



of the surface apparently corresponding to the Middle Grit of 



Nidderdale and Wharfedale, and the lower beds representing the 



Lower Plate group. 



Feet. Inches. 



Strong gritstone of Agra Crags 51 6 



Ochry soft sandstone i 9 



Platy grit 4 6 



Bluish laminated grit and plate 63 



Grey sandstone and blue soft stone 4 ii 



Platy grits and alternations 33 



Solid grit rock 7 



Platy grit 6 



Solid grey sandstone 5 



Dark plate 34 



Hard grey laminated stone 21 



Coal 3 



Hard grey stone with round balls 18 9 



Crinoidal limestone 15 



Hard yellowish cherty stone 6 



Blue plate 5 



Coal I 4 



Total thickness of the Lower Plate group \ 2?e f 



above main coal seam. i 5 ^^ • 



Feb, 1888. 



