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ERRATIC BOULDERS IN THE VALLEY OF THE CALDER. 
BY JAMES W. DAVIS, F.L.S., F.G.S. 
The objects of this paper are, in the first place, to describe 
certain deposits of water-wasbed boulders existing in the 
valley of the Calder; and, secondly, to oflPer an explana- 
tion of the phenomena they present, hoping to gain informa- 
tion from the discussion that may arise from the attempt, 
rather than expecting that the theories I advance will prove 
of scientific value. 
The river Calder has its source in numerous small 
streams draining the moorlands above Todmorden and 
Hebden Bridge. For many miles it runs in a deep valley, 
the sides of which are formed of steep slopes of shale, 
capped by one of the rocks of the millstone grit series. On 
reaching Elland, the millstone grit escarpments are left 
behind, the valley becomes a little wider, and the hills 
bounding it on either hand are composed of some members of 
the carboniferous group. Some of the valleys in this district, 
reaching from Elland to Wakefield, are quite flat and level, 
reminding one very strongly of the appearance of a string of 
lakes joined together by a broad river. Beyond Wakefield 
the river pursues its course through a much flatter country, 
and joins the river Aire near Castleford, its bed being formed 
in the series of rocks forming the upper coal measures. 
Having thus briefly traced the course of the river, and 
noted the geological formations through which it passes, I 
will endeavour to describe a formation of much more recent 
origin than the rocks already mentioned. 
Along the course of the Calder there are beds of gravel 
containing boulders, which occur most extensively in the 
lower parts of the valley. The contained boulders are 
partially of sandstone derived from the surrounding hills, 
and also include rounded blocks of granite, trap, and syenitic 
