132 



Report on Trials of Plows. 



gravels. Its gauge is for less depth than the preceding, Ijut by 

 the assistance of the appliances it may be titted for a depth of 

 twenty inches or more. 



J^/S^ 



Fig. 7 represents a larger plow of tne same plan as the pre- 

 ceding, that by such accessions as are represented in the cut can 

 be regulated for any kind of practicable soil and for any depth 

 between sixteen and twenty-four inches. 



J^i^. 7. 



Deep working maybe divided into two kinds that are effectual, 

 and one ineffectual. The two effectual kinds may be designated 

 by the terms half -trenching and trendiing, or, for marked distinc- 

 tion, thoroHcih-lrenching, The former is often preparatory to the 

 latter. Ineffectual deep-working is when tillage plows, going 

 dee])er th;in their turning gauge, simply raise the soil to let it fall 

 back as if nearly undisturbed. Trenching (or thorough-trenching) 

 consists in reversing the two strata, that is, putting the upper 

 fertile portion below, and lower unfertile portion above, the 

 thickness of the latter being determined by the depth of working. 

 For convenience, we designate these strata h^ the terms soil and 

 subsoil, as well as by the descriptive terms fertile portion and 



