Chap. YI. MOULD OVER THE CHALK. 301 



iiigs would cease to be ejected or would 

 become scanty. 



The following cases show that a consider- 

 able quantity of fine earth is washed down 

 The thickness of the mould was measured a1 

 ])oints 12 yards apart across a small valley 

 in the Chalk near Winchester. The sides 

 sloped gently at first ; then became inclined 

 at about 20° ; then more gently to near the 

 bottom, which transversely was almost level 

 and about 50 vards across. In the bottom, 

 the mean thickness of the mould from five 

 measurements was 83 inches; whilst on the 

 sides of the valley, where the inclination 

 varied between 14° and 20°, its mean thick- 

 ness was rather less than 3*5 inches. As the 

 turf-covered bottom of the valley sloped at an 

 angle of only between 2° and 3°, it is probable 

 that most of the 8'3-inch layer of mould had 

 been washed down from the flanks of the 

 valley, and not from the upper part. But as 

 a shepherd said that he had seen water flow- 

 ing in this valley after the sudden thawing of 

 snow, it is possible that some earth may have 

 been brought down from the upper part ; or, 

 on the other hand, that some may have been 



