DAVIS: SOURCE OF BOULDERS IN CALDER VALLEY. 141 
ON THE SOURCE OF THE ERRATIC BOULDERS IX THE VALLEY 
OF RIVER CALDER, YORKSHIRE. BY JAMES W. DAVIS, 
F.S.A., F.G.S., Etc. 
Four years ago I had the pleasure of reading a paper before 
this Society on the Erratic Boulders in the Valley of the 
Calder. Since then, extended observations have led to a 
confirmation of the views I then laid before the Society. 
The result of those observations forms the subject of this 
communication. 
It may assist a proper understanding of the subject 
if I recapitulate, as briefly as possible, the main facts 
of the case. The river has its source in two or three 
small streams which rise in the hills on the Lancashire 
side of the Pennine Anticlinal. These are joined into one 
stream, and pass along a narrow but deep valley cut at right 
angles to the range of elevated gritstone hills which form the 
boundary between Lancashire and Yorkshire. For five or 
six miles the valley is rarely more than about 200 yards in 
breadth, and on each side the slopes of the hills are extremely 
steep, composed of shales, surmounted by a precipitous grit- 
stone escarpment. At Hebden Bridge the Calder is joined 
by the Hebden ; in its course south-eastwards the valley 
gradually assumes larger dimensions, and south of Halifax 
spreads out into extensive level plains, along which the 
Calder has carved its channel with many devious turnings. 
On reaching the district from Mirfield to Wakefield these 
characteristics are still more apparent, its path being amongst 
the softer beds of the Coal-measures. Below Wakefield to 
the confluence of the Calder with the Aire at Castleford, the 
country generally is of a comparatively flat and uninteresting 
nature. 
The lower reaches of the valley are filled with great 
quantities of gravels, sand, and boulders. At Wakefield 
