316 J. W. Davis — Erratic Boulders of the Colder Valley. 



streams in Dulesgate, Howroyd Clough or Eamsden Clough, tliongli 

 deeply cut, exhibit no sections in which drift can be found. On the 

 western or Lancashire slopes of the hills Boulder-clays and drift 

 occur, often reaching a thickness of 150 to 200 feet. In excavating 

 Hollingworth Reservoir, which is four or five miles west of the 

 summit, and 568 feet above sea-level, extensive beds of gravels 

 were found, which contained marine shells of the genera Fusus, 

 Cardium, Purpura, Neritella, etc. Marine shells in the Drift are not 

 uncommon in other parts of the district. 



The Yorkshire and the Lancashire Calders rise near together at 

 Calder Head. The latter is fed by many small tributaries which 

 have their source on the slopes of the hills eastwards. These tribu- 

 taries have formed deep valleys or doughs, and exposed great thick- 

 nesses of gravel and Boulder-clay. Good examples may be seen in 

 Cant Clough and Hurstwood Brook near Worsthorn, and in the 

 Catlow and Thursden Brooks. The boulders have been derived 

 from the Boulder-clay, which still in many instances is found at the 

 base of the Drift. The latter is composed mainly of Carboniferous 

 limestones and sandstones, with an intermixture of Silurian grits, 

 traps, quartzites, and granites. The Carboniferous Limestone occurs 

 in such abundance that it was formerly very extensively used for 

 burning to obtain lime. The remains of lime-kilns may be seen 

 studding the hill-sides throughout the locality. In the valley with 

 Burnley for its centre the remains of glacial origin occur frequently. 

 The gravels in the valley of the Yorkshire Calder may have been 

 derived originally from the Boulder-beds in these districts, but a 

 glance at the physical features of the district renders this view of 

 the case somewhat problematical. The distance from Todmorden to 

 Burnley is 9 J miles. The two Calders rise at Calder Head four 

 miles from Todmorden. The valley of the Yorkshire Calder, 

 running south-eastwards, is narrow, rugged, and falls rapidly from a 

 height of more than 700 feet above the sea-level at the summit, to 

 about 380 feet at Todmorden. On either side the valley the ground 

 rises rapidly and is surmounted by precipitous escarpments of sand- 

 stone. The Pennine Fault runs in a line with the valley, and has 

 displaced the rocks, so that those on the Lancashire side are com- 

 posed of the Third Grit, the opposite one being thick beds of the 

 Kinderscout Grit. Surmounting the latter, the picturesque groups 

 of weathered rocks, the Bridestones and Hawkstones, ornament the 

 sky-line. Near the source of the stream the Lower Coal-measures set 

 in, and the sides of the valley being, in consequence, of a much looser 

 and more friable nature, landslips have resulted, producing a great 

 number of rounded hillocks. The Lancashire Calder rises and runs 

 in a similar narrow valley falling with equal or still greater rapidity 

 in the opposite direction, the bed of the stream at Burnley being 350 

 feet below that of its source. Beds of gravel are occasionally 

 exposed in the sides of the stream, as at Walk Mill, two miles from 

 its source and 200 feet less in elevation, where, beneath a bed of 

 peat, principally composed of the remains of hazel trees, there is a 

 rough sandy gravel ; the contained stones are for the most part semi- 



