88 THE PRINCIPLES OF 



Again we have formations which have earned the reputation 

 of producing rich soils, and among these may be particularly 

 mentioned alluvial or diluvial soils of mixed origin which 

 accompany the course of rivers, and are especially to be seen 

 around their estuaries, and also forming soils near the coast 

 by the action of tidal currents and tidal deposits. These soils 

 are also of mixed origin, and are therefore sure to be fertile. 



Rich soils are frequently to be found where two or more 

 formations meet together, and where the soils are mingled 

 around the edges of formations. Rich classes of soils are 

 derived from the decay of the lower chalk, the upper greensand, 

 the corn-brash, the lower oolite, the lias clay, the marls of 

 the new red sandstone, the cornstones and marls of the old red 

 sandstone, and the decay of basaltic, trappean, and lava rock. 

 Other formations again yield soils of low average fertility, 

 among which may be mentioned the soils of the upper chalk, 

 of the lower greensand, of the Oxford clay, of the magnesian 

 and mountain limestone, of granite rocks, and of those lower 

 primary stratifications which have been spoken of as the 

 Silurian, Cambrian, and the Laurentian, which frequently 

 rise up into very high mountains. The geological derivation 

 of soils is therefore one of the indications by which we may 

 assist ourselves to come to a conclusion with reference to the 

 quality of soils. 



Before leaving the subject we will see how all the previous 

 considerations must be kept steadily in view the capabilities 

 of the soil as indicated by all sorts of vegetation and growing 

 crops, its texture, its colour, its depth, its sub- soil, its climate, 

 its altitude, its slope or aspect, and its geological position. 

 All these indications ought to assist us in coming to a con- 

 clusion as to the quality of land. 



I want in the next place to show that when we have 

 arrived at a judgment as to the quality of land we are very 

 far indeed from having arrived at its value. There is a very 



