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LECTURE IV. 



On Soils: their constituent Parts. On the analysis of 

 Soils. Of the Uses of the Soil. Of the Rocks and 

 Strata found beneath Soils. Of the improvement 

 of Soil. 



No subjects are of more importance to the far- 

 mer than the nature and improvement of soils; and no 

 parts of the doctrines of agriculture are more capable 

 of being illustrated by chemical enquiries. 



Soils are extremely diversified in appearance and 

 quality; yet as it was stated in the introductory Lec- 

 ture, they consist of different proportions of the same 

 elements; which are in various states of chemical com- 

 bination, or mechanical mixture. 



The substances which constitute soils have been 

 already mentioned. They are certain compounds of 

 the earths, silica, lime, alumina, magnesia, and of the 

 oxides of iron and manganesum; animal and vegetable 

 matters in a decomposing state, and saline, acid or al- 

 kaline combinations. 



In all chemical experiments on the composition 

 of soils connected with agriculture, the constituent 



The fiour of hard wheat is in general superior to that made from soft; and 

 there is no difference in the process of making them into bread; but the flour from 

 hard wheat will imbibe and retain more water in making into bread; and will con- 

 sequently produce more weight of bread: it is the practice here, and which I am 

 persuaded it would be adviseable to adopt in England, to make bread with flour of 

 hard and soft wheat, which, by being mixed, will make the bread much better. 



(Signed) JOHN JEFFERY. 



