1868.] HULL LINES OF ELEVATION. 325 



stone reaches the surface. This axis may be traced from the banks 

 of the river Darwen, near Roach Bridge, through Mellor, Clitheroe, 

 by Skipton and Bolton Abbey into Knaresborough Forest, as indi- 

 cated in Professor Phillips's Map of Yorkshire*. Pendle Hill is in 

 reality the southern segment of the arch. 



North of the Clitheroe arch, there are at least two other lines of 

 elevation, with corresponding troughs, also indicated by Professor 

 PhilHps, and recently surveyed in detail by my colleague, Mr, Tidde- 

 man, to which he gives the names of " the Slaidburn," and " the 

 Sykes anticlinals," the intervening synclinal being formed by Long- 

 ridge Fell. 



» To the south of the Pendle Eange there is a wide trough, giving 

 origin to the Burnley Coal-basin f. The northern side of this trough 

 is formed by the Pendle range itself; and the axis passes through 

 Blackburn, Clayton-le-Moors, Gawthorpe Park, and Marsden, in a 

 general direction from W.S.W. to E.N.E. 



The southern side of this basin is formed by the uprising of the 

 Millstone -grit along a very flat arch, which divides the Coal-mea- 

 sures of the Burnley and Blackburn trough from those of the main 

 coal-field of South Lancashire. As the centre of this arch passes 

 through Anglezark Moor, and through the ancient Forest of Eossen- 

 dale, in an E.IST.E. direction, along which line the strata are nearly 

 horizontal, I propose calling it " the Eossendale Anticlinal " (see 

 figs. 1 <fe 2). To the south of this arch the beds roll over and dip 

 under the South-Lancashire coal-field, which sets in by Eivington, 

 Bolton-le-Moors, Bury, and Eochdale. The general arrangement of 

 these flexures wiU be understood by reference to the diagrammatic 

 plan (fig. 2, p. 326). 



Thus we see that the Carboniferous strata of this part of Lanca- 

 shire were originally forced into a series of foldings along lines 

 ranging a little north of east, and south of west, by the exertion (it 

 may be supposed) of lateral pressure, which seems to have produced 

 its most powerful effects along the line of the Pendle range. The 

 uprising of the beds along the low arch of Eossendale can only be 

 regarded, as it were, as the swell from the distant wave t- These 

 several flexures are expressed in the diagram-section (fig. 1), details 

 being omitted. 



In considering this section, the physical geologist will not fail to 

 observe how the valleys lie in the lines of the stratigraphical hills 

 or arches, and the hills in the lines of the stratigraphical valleys, 

 or troughs, the only exception being the Burnley Basin. The flex- 

 ures are somewhat disarranged in places by transverse faults, but on 

 the whole are well defined. 



Geological age of the Jleceures. — The next point to be determined 

 is the geological age of these fiexures ; and fortunately for our purpose 



* ' G-eology of Yorkshire.' 



t The position of the Burnley Coal-basin, lying between Pendle and Bouls- 

 worth Hills, is shown on the section accompanying Conybeare and Phillips's 

 ' Outhnes of the Geology of England and Wales,' 1822. 



\ Along the Vale of Clitheroe, not only are the beds inclined at high angles, 

 but they are highly contorted. 



