194 



AGRICULTURAL CHARACTERS OF THE OLD RED SYSTEM. 



within reach of the carboniferous limestone, they have found that variety of lime better 

 suited for agricultural purposes, doubtless owing to its being less impregnated with 

 earthy impurities. 



The tracts situated upon the lower member of the System, though not generally of 

 so rich a character as those of the cornstone formation, are yet not so sterile as 

 those of the upper sandstones, for in those districts where argillaceous matter prevails 

 we find stripes of valuable land. Hence* although nearly every portion of the area 

 coloured in the map as Old Red Sandstone has a red surface, the quality of the soil is 

 as various as the many-featured strata which lie beneath it 1 . 



Another cause of diversity in agricultural value, though not connected always with 

 the Old Red System, consists in local superficial coverings of gravel and silt. In some 

 cases, indeed, whole tracts are sterilized by a distribution of bowlder stones and coarse 

 gravel, made up of Silurian and trap rocks, which have been transported from the west 

 and north-west; while in others the finer gravel, is the bearer of excellent crops, and 

 the deep red silt forms plains of rich meadow ground. These features will be further 

 dwelt upon in the concluding chapters, when we come to speak of the alluvial and 

 diluvial phenomena. 



Water is found at various levels and of very different degrees of purity. In some • 

 of the heavy argillaceous districts, it is slightly saturated with red particles, yet I 

 never heard of any deleterious effects arising from its use, and where beds of cornstone 

 and sandstone prevail it is as clear as in any country. 



1 The principal exceptions to red colour, occur at Prescot Bridge, Salop ; in parts near Bromyard, and in 

 certain districts of Pembrokeshire. 



