Vol. 57.] AMONG THE 3IALYERN CAMBRIANS. 173 



Fig. 10. — Section of Grey Shales and diabases at Coal Hill Cottage, 



/■ i h g f a d f b a 



Here five sills, a, c, e, (/, and i, are intercalated in shales, as follows : — 



Thickness in feet 

 M 182. and inches. 



a 1 6 Diabase (top not seen) ; sp. gr. = 2-71. 



b 9 Indurated shale splitting into small rect- 



angular blocks. 



c 1^ to 2 Diabase, rotten; fine-grained at the top ^ 



sp. gr. = 2'51. 

 cf at bottom ... 9 Indurated shale, like 6, 



e 2 3 Diabase, fine-grained at the top and bottom ; 



sp. gr.=2'61. 



/ 5 Shales, baked yellow ; top and bottom mor& 



baked than the middle ; top rery hard, 

 hornstone-like. 

 ^ 3 6 Diabase, fine-grained at the top ; sp. gr, 



k 1 Shales. ' 



i 2 5 Diabase. 



J 10 Shales (bottom not seen). 



20 



The baking of the lower part of /" proves the intrusive nature of 

 the diabase. Outside the garden of the cottage higher rocks are 

 seen, consisting of a thick sill of diabase overlain by thinner bands' 

 of shale and diabase. At the south-eastern end of Coal Hill a 

 similar succession of diabases (M 184) and shales is seen. In the 

 garden of the roadside cottage immediately south of Coal Hill 

 the top of one diabase-sill not less than 6 feet thick, and the 

 bottom of a second not less than 3 feet thick, are seen, separated 

 by about 6 feet of Grey Shale. The beds (M459) dip E. 30= N. at 

 about 48°, and are presumably inverted like those on the road a 

 little farther south. At this point (M 261),^ marked in the writer's 

 map by the dip-arrow 45°, three sills of diabase are seen, the 

 middle one 1 foot thick, overlain and underlain by Dictyonema- 

 bearing Grey Shales 2^ feet and 14 inches thick respectively. The 

 localities just mentioned are the only ones in which the relation 

 of the diabases to the Shales is shown. Thicker masses than those 

 mentioned occur ; as, for instance, M 106, where a thickness of 

 perhaps 15 or 20 feet is indicated. Holl also mentions a sill 35 feet 

 thick in Coal Hill. 



The diabases include coarse-grained (M 106, 182, 372, 459, etc.), 

 medium-grained (M182, 184, etc.), and fine-grained (M 182, etc.) 



^ See also Holl's section, Quart. Journ. Geol. Soc. toI. xxi (1865) p. 89. 



