LECTURE IV,

On Soils: their constituent Parts. On the Analy-sis of Soils. Of the Uses of the Soil. Of theRocks and Strata found beneath Soils . Ofthe Improvement of Soil.

No subjects are of more importance to the farmerthan the nature and improvement of soils; and noparts of the doctrines of agriculture are more ca-pable of being illustrated by chemical enquiries.

Soils are extremely diversified in appearance andquality; yet as it was stated in the IntroductoryLecture, they consist of different proportions ofthe same elements; which are in various statesof chemical combination, or mechanical mixture.

The substances which constitute soils have beenalready mentioned. They are certain compoundsof the earths, silica, lime, alumina, magnesia, andof the oxides of iron and manganesum; and animaland vegetable matters in a decomposing state, andsaline, acid or alkaline combinations.

In all chemical experiments on the compositionof soils connected w ith agriculture, the constituentparts obtained are compounds; and they act as

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