143 



are named by the Royal Agricultural Society as being pre- 

 eminently indications of the value of lands ; yet there are 

 others of equal if not of greater consequence ; for example — 

 1st. A knowledge of the Geology of the land is of the first 

 importance ; that is, not only a knowledge of the range and 

 extent of each formation and its sub-divisions, which may be 

 called Geographical Geology ; but also how far, and to what 

 extent, the various lands depend upon the substratum for 

 their soil, and the local variations in the Chemical or Mineral- 

 ogical character of the substrata themselves : this may be 

 called the differential Geology of soils. For not only do 

 the qualities of land vary from one formation to another, but 

 upon the same formation there is frequently considerable 

 difference in the quality of land, depending upon Chemical 

 difference in the substratum, or upon an intermixture of 

 foreign debris derived from other strata. 2nd. A Chemical 

 investigation of the soil and subsoil will frequently afi'ord most 

 useful indications respecting the value of land. It may be 

 laid down as an axiom, that a soil to be fertile should contain 

 all the Chemical ingredients which a plant can only obtain 

 from the soil, and Chemistry ought to be able to inform us, 

 in unproductive soils, what ingredients are wanting. It also 

 is able to inform us if any poisonous substance exists in the 

 soil, and how it may be neutralized, — when lime, marl, and 

 chalk, are to be used, &c.* 



• Mr. Brakenridge, of Bretton Lodge, who has extensive practice in land 

 valuing, informs me that a mechanical analysis of the soil affords him much 

 assistance ; and he has found, in soils free from stagnant Vi'ater, " that in a 

 " mechanical analysis, the larger the proportion which remains suspended in the 

 *' water, the greater its powers of production will be found, and the less manure 

 " it will require ; — he has found that the best soils are those which, when diffused 

 '* and well stirred in water, and allowed to stand for three minutes, from 20 to 30 

 " — say 25 per cent, is carried off with the water of decantation ; when 30 per 

 " cent, and upwards is decanted off, the soil becomes retentive of water, and 



" consequently wet ; when less than 20 per cent say only 16 per cent, and under 



'* is carried off, it becomes too porous, water passes through it too rapidly, its 

 " soluble matter is washed off into the substratum, and it has a strong tendency 

 ** to become thin and sterile." ) 



