EGGARDON HILL: ITS CAMP AND ITS GEOLOGY. 177 



Browne on "The Origin of the Vale of Marshwood and of the 

 Greensand Hills of West Dorset." If you consult his map and 

 section you will easily trace the circle of these hills Mount 

 Pleasant, Warren Hill, Hackthorn, Lewesdon, Pillcsdon, 

 Lambert's Castle, Hardown Hill, Golden Cap, and Eype Down'. 

 The summits of all these are of greensand, and the geologic 

 interest in the view we now have of them is to reconstruct in 

 imagination the great chalk plain which once extended over 

 them all and the whole intervening space, and then to realise 

 how the forces of denudation, especially the frost and the rain, 

 have removed it all and made the scenery which now lies before 

 us. The process has been much aided by landslips. At 

 Eggardon Farm there is a mass of chalk, now quarried for lime, 

 which must have slipped many hundreds of feet from its original 

 position. When rain falls on porous strata, such as chalk and 

 sand, it sinks lower and lower till it reaches a bed such as the 

 lias clay, which forms the floor of the valleys before us. The 

 water cannot pass the clay, so finds its way to the surface in 

 springs, and flows to the sea in streams and rivers. But before 

 reaching the surface of the ground it does a good deal in the 

 way of excavating and undermining the foundations of the 

 permeable strata through which it can pass ; and the time comes 

 when a mass of chalk or sandy rock will have no sufficient 

 support and will slip to a lower level. We have a splendid 

 example of this in the great landslip between Lyme Regis and 

 Seaton. The large scale on which this took place is due to the 

 fact that cliffs of calcareous sandstone there rest on a bed of clay 

 which slopes towards the sea, so that an inclined plane is formed 

 down which the cliffs slipped when their foundations were 

 sufficiently undermined. But the same agency on a smaller 

 scale has been ceaselessly at work over this whole area, and 

 these hills, while they may be called " everlasting " in com- 

 parison with the span of human life, are really themselves the 

 evidence of the ceaseless changes recorded by geology. 



While, however, the forces in operation to-day are the same 

 as those which have done the whole work in the ages of the 



