310 ON LANDSLIPS. 



The railway passed along from 50 to 100 feet above the 

 bottom of the valley, at which level the geological formation 

 was the inferior oolite, a white rock in nearly level beds. 

 This rock reached to a level of perhaps 150 feet above that 

 of the railway, at which level the fuller's-earth formation, 

 80 feet thick, came in — a dark blue formation, chiefly made 

 up of beds of fuller's-earth clay, but with many beds of 

 blue rock among it. Above this again were the white rocks 

 of the great oolite, which formed the top of the hill. 



The fuller's-earth clays formed the slipping material, and 

 when I first went there, I noticed some old natural landslips 

 here and there all down the valley. It is not a bad ground, 

 however, and only slipped where it had great provocation ; 

 that is where, in the steep valley slopes, copious water- 

 springs burst forth. These slips, consequently, came to a 

 stand with comparatively steep, rounded contours, and 

 caught the eye of the observer instantly. 



I may now proceed to describe the most interesting and 

 instructive one amongst those affecting the railway. The 

 rough sketch of it, which I have made from memory, will 

 help you to understand its position. 



This slip takes its origin in a large wood, many feet above 

 the railway, where the slip, in its origin, spreads out to a 

 breadth of a quarter of a mile or more. In seeking through 

 the wood for the caase of the slip, I found there three 

 separate and considerable water-springs, which came to the 

 surface at different places ; but, after running a few yards, 

 they all disappeared again through the broken ground. 

 These, no doubt, caused the slip. As this slip, however, in 

 its subsequent steep descent, passes over the strong lower 

 oolite, its boundaries become greatly narrowed, and the slip, 

 now only 50 yards or less wide and 30 or 40 feet deep, passes 

 down a steep gully in the rock below, till it arrives at the 



