dvring the last Four Ycar^^ 189 



occasioned nearly as much labour to the horses as when actually 

 doing' its work. The friction on so smooth a surface as wet clay 

 cannot be mvich ; the strain must be occasioned, I believe, by its 

 adhesion. The strength of this adhesion is shown by the diffi- 

 culty which a labourer finds in digging strong clay, from its 

 adhering when wet to the back of his spade. On such lands 

 in this neighbourhood a Avooden mouldboard is used, the clay 

 being found to adhere less strongly to wood than to iron.* 

 The length of a mouldboard must increase adhesion as well 

 as friction, but practically on clay-land it is impossible to use a 

 short mouldboard, because, if we endeavour to throw such land 

 too suddenly over, it will roll before the plough when it is very 

 wet. This happens sometimes indeed even with the long mould- 

 boards now used on such ground ; and consequently it is very 

 difficult to make an improved plough for such clays. But for 

 other soils I think plough-makers will do well to regard diminu- 

 tion of friction as a leading principle of their attempts at improve- 

 ment, varying its application according to the land which their 

 ploughs are intended to work : for we never can have a standard- 

 plough suited to all descriptions of land. If land be light and 

 free, the plough should be short above ground, that the horses may 

 be nearer their work, and short below, that there may be less 

 friction. Hart's is such a plough ; and is now generally used on 

 such land in this neighbourhood : but if you put this plough on 

 strong or stony land, it will rise out of the ground when at work. 

 On strong or stony land a wheel-plough must be long in the 

 beam, that the horses may hold it down when they pull it ; and 

 taper in the breast, that it may undermine the obstacles which it 

 meets. Different depths of ploughing again require a different 

 shape of the mouldboard. These, however, are matters for the 

 makers of ploughs: the question for farmers is the advantage to 

 be derived from the use of light ploughs. Where the difference 

 is between the draught of two horses and of three, that advantage is 

 of course very clear : even where it is less, the improvement may 

 bring the plough within the command of two horses, upon land which 

 before was too strong for a pair. Where four horses are the usual 

 team, pair-horse ploughing may be impossible, and its advocates 

 were wrong when they asserted that there is no land which two 

 horses are unable to master. But in many districts, where three 

 horses were the usual number, country ploughing-matches have 

 tended to introduce the two-horse system. On the first occasion 



'■^ The same soil which when wet adheres to the plough becomes exceed- 

 ingly hard when dry, because its particles cohere together, and then the 

 splitting action becomes a source of draught: hence, of course, the difficulty 

 of ploughing most soils when they are dry, which becomes impossibility on 

 a strong clay. 



