J. W. Davis— The Valley of the Calder. 607 



Sliapfell to the position in which it is found. The evidence that it 

 has been conveyed by ice is also very conclusive. Where the boulders 

 of Shap granite, or those from other localities, are found imbedded in 

 clay, they are covered with fine scratches. Now the only agent with 

 which we are acquainted which can scratch the stones in this pecu- 

 liar manner is the grinding and rubbing action of a mass of moving 

 ice, such as constitutes glaciers. The boulders in Lancashire and the 

 more eastern parts of Yorkshire are scratched in the way indicated ; 

 but those in the Calder valley are not scratched or striated, and 

 there is no evidence that a glacier ever occupied this valley. The 

 way these erratics appear to have got into the valley is as follows. 

 They were brought by glaciers into the valley of the Ouse along 

 with glacial clay, and deposited there. After a while the level of 

 the land was lowered, and the glacial deposits were subjected to the 

 action of the waves. The boulders were washed out of the clay, and 

 rolled about the bottom of the sea, until the scratches were oblite- 

 rated and the corners worn off. 



At this time the valley of the Calder was submerged. Its channel, 

 subject to the fury of the waves, would soon become much deepened 

 and wider. The shales beneath the Grit-rock, from their loose and 

 incoherent structure, would prove an easy prey to the waves, and be 

 readily washed out. The Grit-rocks above them are broken into 

 huge cubes by fractures extending vertically in all directions, and, as 

 soon as their support was gone, these cubes of rock would fall down, 

 and, subjected to the action of the waves in their turn, would be 

 broken into smaller pieces, the corners and sharp edges removed, 

 and they would form the boulders we find at the present time filling 

 up the valley. Intermixed with them, the boulders of foreign 

 origin, washed up by currents from the not far distant valley of the 

 Ouse, would be deposited at the same time. After a while, on the 

 re-emergence of the land, the flat plains, formed as described, would 

 exist in very nearly the form we see them at the present day. 



I have reached the concluding portion of my subject, and have 

 only a little more to say respecting the sub-aerial denudation that is 

 always in progress, at a greater or less rate. 



The principal agents are rain and streams, springs and frost. 

 Their effects in forming the contour of the surface may be seen 

 everywhere. Valleys are seen cut deep into the solid rock, and still 

 deeper into the shales below. Landslips fi'equently occur, caused 

 by the underlying strata being washed out by springs ; or the rocks, 

 having been saturated with water and subjected to the action of 

 frost, are, by the expansion of the water during freezing, forced off 

 in masses which lie strewn on the hill-sides. I have already 

 remarked on the liability to erosion by the sea of the beds of rock 

 in the valley of the Calder. We find, universally, that a bed of grit 

 overlies a bed of shale. You will find such to be the case in the 

 sections exposed in Copley valley. 



The sandstone acts as a huge reservoir for collecting and holding 

 water. In wet, rainy seasons, such as we have experienced during 

 the past summer, the sandstones are like great sponges ; all the inter- 



