OKIGIN OF KOTHAMSTED SOIL 25 



the clay, and also the flints, being blackened by manganese 

 oxide. Masses of this stiff clay-with-flints form the subsoil in 

 places; elsewhere light sands or red loamy sands with or 

 without black flint pebbles, or masses of pebbles alone, form 

 the immediate subsoil ; again, grey or mottled clay or loam 

 with occasional pebbles or free from stones, or with a gravelly 

 pocket here and there, extends for some distance, immediately 

 beneath the soil. These accumulations occur in irregular 

 juxtaposition owing to the piped surface of the chalk, and in 

 places there is a kind of marl formed on the slopes by the 

 weathered rubbly chalk mixed with earth." 



" Covering these subsoils there is a soil of grey flinty or 

 pebbly loam, 10 inches or more in thickness, and varying in 

 character according to the number of stones in it; in some 

 cases rough and unworn flints prevail, elsewhere there is an 

 admixture of pebbles ; and over some areas the soil consists of 

 loam with comparatively few stones. In all cases, excepting 

 on the chalk slopes and in the valley bottom, the soil is to be 

 regarded as a heavy mixed soil, for the subsoil is in the main 

 a heavy clay ; and were it not for the fact that the chalk here 

 and there approaches very near to the surface of the higher 

 grounds, the land would be much wetter after rain than is the 

 case. These underground pinnacles of chalk, and the pockets 

 of sand and gravel, act as dumbwells for the surface 

 drainage." 



Notwithstanding the irregularity of the subsoil, the 

 agricultural character of the soil is fairly uniform all over the 

 estate ; some fields work rather more heavily than others, and 

 the proportion of stones lying on the surface varies somewhat, 

 but these differences are comparatively unimportant. The soil 

 passes into the subsoil without any sharp line of distinction, 

 and the distribution of flints in the subsoil is very irregular, 

 while the solid chalk is reached at depths varying between 8 

 and 12 feet. 



The following Table (XI.) shows the mean results obtained 

 for the weight per cubic foot and the weight per acre of stones 



