58 THE PRINCIPLES OF 



cross the magnesian limestone, because it happens to be 

 omitted in that particular route, but cross the coal measures, 

 after which we shall arrive at Manchester. Now these are 

 remarkable facts, and it is of great assistance in coming to a 

 conclusion as to the distribution of soils in this country. 



It would take us a long time to go through the peculiarities 

 of the various soils resting upon different geological strata. 

 But let me recommend it as a study and as a most 

 important one. It has never since been prosecuted with 

 such thoroughness as it was by the late Professor John- 

 stone of Durham. In Johnstone's Agricultural Chemistry, 

 now brought out in a later edition by Dr. Cameron, but 

 especially in the old edition of Johnstone's Agricultural 

 Chemistry, is to be found a most painstaking account and 

 comparison between the nature of the soil and the geological 

 formation from which that soil is derived. 



There is no doubt a strong resemblance between soils, 

 whether found in one county or another, which have the 

 same geological horizon. If the idea is once grasped that 

 there is a close relationship between the succession of rocks 

 in the geological section of this country and the soils which 

 successively occupy the surface of those rocks, that is the 

 idea which I wish to impress. 



Certain formations give soils of a high average fertility, 

 and other formations give soils of a low average fertility. 

 Wherever we have a mixed soil, formed by the blending of 

 two or more formations, there we are likely to have a fertile 

 soil. In other words, the soils which occur at the margins 

 where formations meet together the soils which occur at 

 the confluence of two formations are usually of better 

 character than soils which are in the -centre, or well into 

 the area occupied by such formations. For instance, soils 

 which are derived from the London clay mixed with the 

 chalk are more fertile than either chalk or London clay soils. 



