CHAP. VI.] CARBONIFEROUS PERIOD. 81 



thinks it was formed in a narrow channel or strait which 

 separated a smaller northern island from a larger southern 

 one, and that the pebbles were drifted by a current from 

 the south, and accumulated chiefly at the eastern end of the 

 supposed channel, where their further northward progress 

 was impeded. 



Mr. J. G-. GToodchild, however, informs me that he differs 

 from Mr. Ward's view, and believes the pebbles were 

 derived from northern sources. The Silurian rocks of 

 Westmoreland are strongly cleaved, and though a few of 

 the Mell Fell stones are undistinguished from Westmore- 

 land rocks, yet many pebbles of uncleaved mudstones 

 occur, together with other rock-fragments which are unlike 

 any in the Lake District, but can be matched with rocks in 

 the south of Scotland. A further proof of a northerly 

 current is found in the fact that the conglomerates of 

 Tebay (further south-east) contain stones and boulders 

 that have certainly come from the Lake District, and their 

 percentage increases up to a certain point as the beds are 

 traced southward. Again, along the Pennine escarpment 

 the basement beds contain stones derived from the Lower 

 Old Red Sandstone of the Cheviot district, and these must 

 also have come from the north. 



Mr. G-oodchild concludes, therefore, that the drift of the 

 pebbles was from the northward, and, as regards the sub- 

 mergence of the land, he holds that there was a ridge of 

 high ground extending across the Pennine and Lake Dis- 

 tricts, which formed an island at the time when the con- 

 glomerates and sandstones were being deposited, but that 

 it was rapidly submerged and entirely covered by the sea 

 before the epoch of the Yoredale Beds. The position of 

 the ridge can be determined by drawing a line round the 

 points where the Lower Carboniferous Beds are thinnest. 

 Thus the beds below the Toredale series, along the Pennine 

 range, are found to be thinnest in Teesdale (400 feet) and 



G 



