188 J. AITKEN ON THE DISTRIBUTION OF DRIFT 



For a full and clear comprehension of this subject, it will be 

 necessary to glance at the physical and geographical features of the 

 district and to trace their relation and bearing to the surrounding 

 country. In treating of this branch of the subject, our attention 

 will be principally directed to that part lying between Burnley and 

 Littleborough on one side, and Todmorden on the other — a district 

 embracing the deep valleys of Cliviger and Walsden, in which are 

 contained the two lowest watersheds in the whole of this central 

 range of hills. 



If, then, we take Todmorden as the central point of the district, 

 from which to commence our observations, we shall find that that town 

 is situated almost on a line with the highest summits of the Pennine 

 Hills, in a deep gorge at the junction of the two streams which flow 

 through the two defiles already mentioned, and on the main axis of 

 that series of dislocations known as the great Pennine fault, which run 

 in a line roughly coincident with the Walsden and Cliviger valleys, 

 and the effect of which has been, not only to fracture and break up 

 the rocks to a marvellous extent, but also to cause a reversal in the 

 dip of the strata, those on the east dipping at an angle of about 

 5° to the S.E., and those to the west declining at an angle of from 

 20° to 45° to the W.S.W. 



Starting from this centre, three valleys radiate in different direc- 

 tions, in lines almost equidistant from each other :— one stretching 

 off through Walsden to Littleborough for a space of about 5 miles in 

 a direction a little W. of S. ; another taking a N.W. course through 

 the sinuous gorge of Cliviger to Burnley, a distance of about 8 miles ; 

 whilst the third, the valley of the Calder, takes an E.N.E. direction. 



The appearance thus presented, when traced on a geological map, 

 reminds one forcibly of the device which characterizes the Manx 

 copper coinage. By an examination of these arms, we shall find 

 that they are three deep, narrow, rocky, tortuous channels, hemmed 

 in on every side by massive walls of rock, cut into at intervals 

 along their course by the entrance of tributary streams. 



The watersheds of the Walsden and Cliviger valleys are at a com- 

 paratively low level, that of the first having an altitude of 027 feet 

 above sea-level, and being eaten into to a depth of 330 feet below 

 the shoulder, or first platform bounding the valley*; whilst that of 

 the second is crossed at an elevation of 768 feet, and is excavated to 

 a depth below the immediate country of 475 feet, a depression which 

 would be greatly increased if the summit-level of the surrounding 

 hills were taken as the datum-line for measurement. 



The valley of the Calder, which forms the line of drainage through 

 which the waters of the aforesaid tributary valleys, from their 

 junction at Todmorden, pass off to the German Ocean, is cut in to 

 a depth considerably in excess of those already described. 



If, then, we view these valleys in relation to the initial period of 



their formation, structure, and physical characters, the total absence 



of drift or other indication of ice-action within their boundaries, or 



the marked contrast presented in the configuration of these and other 



* Prof. Hull, Geol. Mag. vol. iii. p. 475. 



