VARIATIONS IN PASTURES 143 



on the Lower Lias here is an extremely stiff unyielding clay, 

 blue or yellow lias clay subsoil being not far below. At the 

 same time, a considerable part of this district which lies 

 at a low elevation is covered by an alluvial deposit, varying 

 from a few inches to many feet in depth ; pastures on this 

 alluvial soil are invariably free from any tendency to cause 

 scouring even though the typical Lower Lias clay may lie not 

 far below the surface. The division between good and bad 

 land is in many places very sharp and affords an accurate 

 indication of the boundary between lias and alluvium. Where 

 the layer of alluvium is deep the differences in the surface 

 soils of the two kinds of fields are very obvious ; and even 

 where the soils are in most respects very similar the surface 

 of the good fields is noticeably darker in colour and looser in 

 texture and, further, the ground has an indefinably different 

 and more springy " feel " to the foot. 



In order further to investigate this difference in texture 

 between sound and "teart" land, determinations of the densi- 

 ties ! of some of the soils in situ were made. With few excep- 

 tions the surface soils of the sound fields show consistently a 

 definitely lower density than those of "teart" fields from the 

 same neighbourhoods. The sound soils have also a greater 

 capacity for holding moisture. 



Ordinary chemical analysis of both types of soil has not 

 revealed anything that could account for the observed effects 

 and there is no obvious peculiarity in the composition of the 

 "teart" fields. A large number of samples were also submitted to 

 mechanical analysis, the result being that all the soils, whether 

 from good or bad land, were found to be of the same general 

 type, so that the observed differences in physical condition and 

 texture cannot be accounted for by referring them to the 

 ultimate mechanical compositions of the soils. 



These analyses have, however, brought out the fact that 

 there is, almost invariably, a considerably higher percentage of 

 organic matter in the good soils ; and there is no doubt that, to 

 a great extent, the dark colour, the texture and the different 

 appearance and " feel " of the soil of these fields is due to the 

 influence of the higher proportion of organic matter on the 

 nature of the compound soil particles. 



The only significant difference discoverable between sound 

 1 Details are not yet published. 



