130 OPERATIONS OF TILLAGE. 



share slightly to the left-hand side. By these means, 

 however, the labor of draught is increased, and care must 

 therefore be taken that this tempering of the irons, as it 

 is frequently called, be not in any case carried further than 

 is necessary to correct the defects of the instrument. All 

 that is necessary beyond this is effected by changing the 

 position of the Une of draught, by means of the bridle on 

 the beam. 



" With regard to the depth to be ploughed, this, we 

 shall see in the sequel, depends upon the kind of crop to 

 be cultivated, and other circumstances. It has been 

 shown that a furrow-slice of ten inches in width requires a 

 depth of seven inches, that is, a depth of about two thirds 

 of the width, in order that it may lie at the angle of 45°. 

 But, although it is necessary to proceed upon this prin- 

 ciple in forming a plough, we cannot regulate the width 

 to the depth in this manner in practice. It is not neces- 

 sary that the depth should be to the width in the propor- 

 tion of two to three, or that the sod should be precisely 

 at the angle of 45°. In the field, all that can be arrived 

 at is a kind of approximation to the true proportions. 

 When the sods are considerably too wide in proportion 

 to their depth, the ploughman will be admonished of this 

 by their lying too flat, and too slightly overlapping each 

 other. When their depth is considerably too great in 

 proportion to their width, they will stand too upright, and 

 be apt to fall back again into the furrow. 



''- The medium depth of good ploughing may be held 

 to be seven inches. When circumstances, as the kind 

 of crop, and the nature of the soil, do not require deep 

 ploughing, the depth may be less ; but it will be consid- 

 erable in those cases to be afterwards adverted to, when 

 deep ploughing is from any cause expedient. 



" In the moist climate of Britain, and indeed in 

 most parts of Europe, it is necessary to form the ground 

 into what are termed ridges, so as to permit the water 

 which falls upon the surface to find a ready egress. And 

 even in lands so dry that little injury will result from stag- 

 nating water, such ridges are generally formed, on account 

 of their convenience in the different modes of tillage. 



