EARTH'S SURFACE METEORIC ABRASION. 73 



grass land and creeping up the hill. On the other 

 hand, if a section is cut down a hill similarly cir- 

 cumstanced, except that it has been tilled for a con- 

 siderable time, the results will be different, and the 

 denudation quite apparent ; for the surface soil will 

 be much reduced in thickness on the slope and 

 summit, it being carried down the hill, and even 

 found overlapping and lying on the peat in the flat 

 below. Such a section will also give a record of the 

 number of times and periods the hill has been in 

 tillage and under grass ; for the peat and surface soil 

 at the base of the slope will be found intercalated 

 according to the number and length of the times the 

 hill was exposed to the denuding influences. It may 

 be said, that although meteoric abrasion does not 

 denude the surface of the grass land, yet the water 

 percolating through the soil increases its depth by 

 gradually rotting the subsoil. This also seems to 

 be disproved, as it is not of uncommon occurrence, 

 when draining grass land formerly tilled, to find 

 lying on the surface of the subsoil the old sods. 

 This could not be the case if the atmospheric influences 

 had the power of increasing underneath the surface 

 soil of grass land. Different authorities have shown 

 that in some localities " stones grow on the surface;" 

 that is, the surface of some grass land gradually 

 becomes covered with stones. This, however, is only 

 the exception to the general rule, and in moist climates 



