Chap. VI. MOULD OVER THE CHALK. 301 



ings -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 

 points 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 60 yards across. In the bottom, 

 the mean tbickness of the mould from five 

 measurements was 8 3 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 eartb may have 

 been brought down from the upper part ; or, 

 on the other hand, that some may have been 



