THE BASAL ROCK-GKOUrs 0J-' SHKOPSIIIKD. 115 



consisting mainly of quartz and rod felspar. It varies in the 

 degree of coarseness between microscopic grains and bits of ^ 

 inch in diameter, and this character gives us the means of deter- 

 mining the strike. At two spots on the western side of the glen, a 

 clear strike may be made out by following the coarse seams. In 

 one case the direction is E. and W., in the other N.W. by W. The 

 dip is vertical or very high. At the southern end of the section the 

 grit is almost black, and this peculiar variety crops out on the 

 opposite slope about 50 yards to E. by a little S. The strikes agree 

 therefore in a general way with the usual strikes of the volcanic 

 rocks in the Cardington mass. See the accompanying map, facing 

 p. 120. 



The other locality is in the quarries at Woodgate, where is exposed 

 the clear series of rhyolites and grits described in my 1879 paper 

 {op. cit. p. 658). These rocks are admitted by Prof. Blake to belong 

 to the true volcanic group. I have recently detected at the back of 

 this quarry, at the western extremity, and almost on the strike of 

 the green grits, a reddish grit, composed of quartz and red felspar, 

 with some bits of rhy elite. In hand-specimens it is seen to be quite 

 of the ordinary Uriconian type. The annexed section (fig. 2) shows 

 the relation of the grits of these two localities to the associated 

 volcanic rocks. 



Eig. 2. — Section across the Hope-Bowcller mass. 



N". S. 



g. Grit 



(b) Caer Caracloc. — The mass of grit near the south-western end 

 of the ridge is regarded by Prof. Blake as a mere surface-patch. 

 There is, however, very clear proof that it is intercalated in the 

 Uriconian. In one place it is distinctly bedded. The reddish 

 variety alternates in regular seams with a dark grit, with a shaly 

 band, and with a fine-grained compact rock, like halleflinta, but 

 whether igneous or aqueous is uncertain. Prof. Bonney inchnes to 

 the former belief. 



These beds dip very clearly to the N.E. Both above and below 

 numerous exposures of the ordinary hiillefiinta of the district are seen 

 to crop out, with the same dip, or, where the dip is not apparent, 

 with a strike to N.W. or N.N.W. 



(c) Charlton Hill. — Clearer evidence for the pre-Cambrian age of 

 the grits and conglomerates could hardly be desired *. After Prof. 



* Quart. Journ. Geol. Soc. vol. xxxv. (1870) p. finr,; vol. xlii. (I88li) p. 483. 



