54 AGRICULTURE. 



low furrow. If you wish a deep furrow, diminish 

 the angle, and vice versa: but this angle should in 

 no case exceed from 18 to 24 degrees. 



The resistance made to the plough being produ- 

 ced less by the weight of the earth than by the co- 

 hesion of its parts, it is evident that the head should 

 be shod with iron, and rendered as smooth as pos- 

 sible. This remark applies equally to the soc and 

 to the mouldboard. 



3d. The soc, in its widest part, should be larger 

 than the head. It has different shapes in different 

 countries. In some is given to it that of an isosce- 

 les triangle ; in others, that of the head of a lance ; 

 in Biscay, that of a crescent ; and in Poland, of a 

 two pronged fork. But, whatever be its shape, it 

 should be well pointed and polished, enter the earth 

 with facility, and cut it easily. 



4th. To the mouldboard some workmen give the 

 shape of a prismatic wedge ; others make the up- 

 per part convex and the lower concave : while 

 many make it entirely flat. In stiff soils, the semi- 

 cycloid is the form to be preferred; and in loose, fri- 

 able soils, the semi-ellipsis.* The iron mouldboard 

 has great advantages over the wooden, particularly 

 when it, the shear, and the soc, form one piece, as 

 in the ploughs of Mr. Cook. 



It is a general opinion, that a heavy plough is 

 more disadvantageous than a light one ; because 

 the draught of the former, being greater, will be more 

 fatiguing to the cattle ; but the experiments of the 

 agricultural society of London establish a contrary 

 doctrine, and show that, in light grounds, the labour 

 is more easily and better performed with a heavy 

 than with a light plough. 



5th. The coulter is a species of knife inserted in the 

 beam, and so placed before the soc as to cut the sod. 

 It is susceptible of being raised or depressed at will. 



6th. The handles of the plough ought to be made 

 * See Arbuthnot on Ploughs, 



