124 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [NoV. 



No. ft. in. 



3, Laminated sandstone 5 4 



2. Laminated arenaceous shale 3 



L Laminated sandstone 11 



The highest bed of the millstone grit, a flaggy sandstone. 



Total thickness of coal-measures... 1860 



Analysis of the preceding Section. 



ft. in. 



Arenaceous and argillaceous shales ... 1127 3 



Underclays .*...... 99 6 



Sandstones 562 



Coal 37 



Bituminous shales 26 5 



Carbonaceous shales 3 3 



Limestones 3 11 



Conglomerate 8 



1860 



Prom this analysis it appears tliat the argillaceous and arenaceous 

 shales occupy about two-thirds of the whole section ; they are gene- 

 rally of a grey or bluish grey colour, but occasionally red, purple, or 

 brown, as specified in the section. Their composition is variable, 

 passing from soft unctuous clays, through every conceivable grade, 

 into arenaceous beds so highly charged with siliceous matter, as to 

 be with difficulty distinguished from fine-grained sandstones. They 

 are generally laminated, but there are many beds, some of great thick- 

 ness, which present no traces of lamination ; these disintegrate rapidly 

 when exposed to the air, and might more properly perhaps be desig- 

 nated marls. Viewed at some distance from the water the parallel- 

 ism and persistence of the shale beds appear to be perfect ; it is only 

 by a close examination that we occasionally discover a bed of shale 

 replaced by sandstone, as in the annexed cut, where the bed of red 



Fig. 1. 



Sandstone. Shale 215. 



High-^ 

 water \. 

 line. J 



Shale 213. 



Shale 214. 



shale. No. 214, terminates at the height of eight feet above high- water 

 line, and is replaced by hard laminated sandstone, which overlaps the 

 edge of the shale. The underside of the sandstone, in contact with the 

 subjacent shale No. 213, presents markings of fucoids, which cannot 

 be observed upon the underside of the red shale, showing, that in the 

 interval between the deposition of the red shale and the sandstone 

 unconformably upon its edges, a layer of sea-weeds had been spread 

 over the uncovered portion of the surface of the shale No. 213. 



The red shales are very irregular in thickness ; thin beds of twelve 

 or fifteen inches sometimes increase to three or four feet in depth 



