1808.] HULL — LINES OF ELEVATION. 323 



and the same qualities belonging to the gritstones in the north, we 

 may venture to suggest, as an explanation, the entrance of two 

 distinct currents or primeval rivers, one on the west bearing sedi- 

 ment from the sui'face or region of argillaceous slate, the other from 

 the north bearing almost wholly the granular detritus of regions 

 abounding in gneiss and mica slate "*. Though this distinction in 

 the distribution of the claj^ey and sandy members of the formation 

 is doubtless correct in its application to Yorkshire, I doubt if it 

 holds good with reference to the whole of the north and centre of 

 England, where the thinning away or the swelling out of both sets 

 of beds seems to proceed pari passuf. It therefore seems to me 

 clear that we must attribute the source of the sediment generally to 

 one and the same primeval Atlantis ; and this view is strengthened 

 by the fact that the Carboniferous sedimentary strata swell out 

 towards the north-east of America on the shores of Nova Scotia, 

 and tail away towards the south and west of that continent. 



3. Observations on the Relative Ages of the Leading Physical Fea- 

 TTiRES and Lines of Elevation of the Cakboniferotjs District 

 of Lancashire and Yorkshire. By Edward Hull, Esq., M.A., 

 F.R.S., F.G.S., of the Geological Survey of Scotland +. 



The approach to completion of the Geological Survey of South and 

 Mid-Lancashire enables me to draw up the following observations 

 on the ages of its physical features. This district, it may be ob- 

 served, lies immediately to the south-west of that which has been 

 so faithfully illustrated by Professor Phillips in his well-known 

 * Geology of Yorkshire.' 



The most prominent feature of the tract now to be considered is 

 Pendle Hill (1831 feet); and as this hill is but the culminating 

 point of a long range of parallel escarpments, physically one, stretch- 

 ing through a distance of 30 miles from W.S.W. to E.N.E. in Lan- 

 cashire, and continued into Yorkshire, I shall take the liberty of 

 applying the term " Pendle Eange," to the whole of this line of 

 hills. 



This range commences at Parbold Hill, near Ormskirk, on the 

 south-west, takes a straight course into Yorkshire by Hoghton Tower, 

 Blackburn, and Whalley, and, forming the south-easterly side of the 

 Yale of CKtheroe, continues its course towards Colne and Skipton. 

 It generally consists of a double group of ridges, often rocky and 

 serried, ranging in parallel lines, with intervening valleys. 



The chain, when cut through transversely near its centre, presents 

 in structure the segment of a great arch (see fig. 1) of which the 

 axis passes by Clitheroe, and along which the Carboniferous Lime- 



* ' Geology of Yorkshire,' New Edit., Part 2, p. 188. 



t For instance, the uppermost bed of Millstone-grit, or the Rough Rock, 

 reaches a thickness of about 450 feet at Hoghton Towers, near Blackburn, one 

 of the most westerly points to which we can trace it ; while its average thickness 

 is about 100 or 150 feet. 



t Communicated with the consent of the Director-General. 



