Oil the Agricultuixil Geology of England and Wales. 495 



occupied by its upper formation or quartzose conglomerate and 

 sandstones, the soil arising from their disintegration is light and 

 sharp, and far from productive ; that on the cornstone group the 

 disintegration of their calcareous nodules, and the admixture of 

 their component parts with the argillaceous and siliceous particles, 

 produce the rich red argillaceous soil of Herefordshire ; that the 

 soils derived from the quartzose members of the lower sandstones 

 are not generally so fertile as the cornstones, but that when 

 argillaceous matter prevails they produce stripes of valuable 

 land. Hence, although nearly every portion of the area 

 coloured red on the map has a red surface, the quality of the soil 

 is as various as the many-featured strata which lie beneath." 



This is the substratal view of the origin and relations of the 

 surface soil : he adds, however, that another cause of diversity 

 arises from the local superficial covering of gravel and silt ; some 

 tracts being wholly sterilised by the distribution of boulder stones 

 and coarse gravel, made up of silurian trap rocks, transported 

 from W. and N.W. ; while in other parts fine gravel bears 

 excellent crops, and the deep red silt forms plains of rich mea- 

 dows. The same remarks are repeated in describing the soils 

 resulting from the debris of the different members of the silurian 

 system ; pointing to the operations of water, by which the surface 

 has in many instances been strewed with gravel and fine loam, and 

 in others with coarse gravel and boulders. The finer deposits are 

 assigned to the valleys adjacent to the great rivers ; the coarser 

 deposits chiefly to mountain sides. After discussing how far the 

 natural vegetation of a country is dependent on its geological 

 characters, he points out that the lithological characters of a rock 

 are of more importance than its place in the series, and that 

 plants affecting rocks of a particular mineral composition grow 

 upon rocks of that composition, no matter what their geological 

 age; and he concludes that '''after all, substratal influence is 

 constantly obliterated by over-lying detritus ; and that it is there- 

 fore difficult, except on naked and stony ridges, to trace any con- 

 nexion between the subsoil and the plant." 



I shall conclude, then, with the proposition with which I 

 commenced ; that as geological researches are at present con- 

 ducted, an essay on the agricultural geology of England and 

 Wales must treat of it rather as it is not, and as it ought to be, 

 than as it is. Between agriculture and geology there is an 

 intimate connexion ; but it is through the medium of the super- 

 ficial deposits, and, when they are absent, through the mineral 

 characters of the rocks. Maps which neglect both these, and 

 exhibit little more than the areas occupied by the out-crops of 

 certain groups of fossils, are nearly worthless for the purposes of 

 agriculture. 



