NORFOLK SOCIETY. 471 



as examples. By proper compression of the soil and judicious 

 manuring, it has been found practicable to raise good wheat 

 on soils of so light a character that they were formerly thought 

 not adapted to this crop. 



It has been before remarked, in regard to giving the requisite 

 solidity to too light soils, that the harrow is used by road ma- 

 kers for consolidating the earth. Any one can be satisfied, by 

 an experiment, that it produces this effect. A friend of the 

 writer, who has paid much attention to this matter, explains 

 the consolidating effect on the principle of atmospheric pres- 

 sure, — the passage of the harrow-teeth through the soil causing 

 a partial vacuum, which occasions a forcible rush of the air. 



But some one may still be inclined to ask, — Why should it 

 be necessary to take so much pains to compress sandy soils, 

 for the production of wheat, when equally as great pains are 

 recommended for making stiff soils lighter ? The general rea- 

 soning before given, may be deemed a sufficient answer; but, 

 it may be further said, in explanation of the opposite practices, 

 that a particular state of the soil, as to lightness or solidity, is 

 required, and that the pressure given in the one case, or the 

 lightness attained in the other, only brings the diflerent kinds 

 of soil to the proper degree of consistence. 



We have now considered the two main divisions of our sub- 

 ject, — the ploughing of stiff and of light soils. To illustrate 

 the principles involved, it was necessary to present the opposite 

 points in a distinct form. In regard to the intermediate de- 

 scriptions of soils, it is obvious that the mode of tillage should 

 correspond to their character, in proportion as they approxi- 

 mate to either of the two extremes of lightness or heaviness. 



3. Trench Ploughing. This is neither more nor less than 

 deep ploughing. The operation merely buries the surface soil 

 and brings up the subsoil in its place. The principles which 

 have been adverted to, in considering the preceding parts of 

 our subject, point pretty clearly to the circumstances under 

 which trench ploughing should be practised. They show that 

 it is where the soil is rich to a greater depth than is reached 

 by the ordinary mode of ploughing, — or, to speak more defi- 

 nitely, where the substratum is richer than the surface, — that 

 this mode would be attended with advantage. Such soils are 



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