Experimental Inquiry on Draught in Ploughing. 229 



other hand, a singular want of pHancy for adapting itself to deep 

 ploughing. 



It will be seen by this table that on sandy land, at least, the 

 draught increases but slowly when the furrow is deepened. As 

 this is an important point in the practice of husbandry, and as it 

 is laid down, on the contrary, in our books that the draught in- 

 creases rapidly, or, in mathematical terms, according to the squares 

 of the depth, — that is to say, that if the draught at 4 inches be 1 8 

 stone, at 7 inches, it will be as 49 to 16 or 54 stone, I put the 

 question again to the test two days later, upon a poor moory soil, 

 with Ferguson's Scotch plough. We began with a 5-inch furrow, 

 and w^ent lower each furrow until the plough was a foot in the 

 ground. The increase of draught was as follows ; — 



Furrow 9 inches wide. 

 Depth iu Inches, 



5 



7 

 8 

 9 

 10 

 11 

 12 



Draught in 

 Stones. 



23 

 22 

 25 

 30 

 31 

 40 

 50 

 50 



This is a difficult experiment to make, and some of the numbers 

 show that we did not succeed always in keeping the proper depth 

 of our furrow. Still they are near enough to prove that the law 

 of increase laid down in books is altogether erroneous ; since, if 

 that were the true rate, the draught at a foot would have been not 

 50 stone, but 132. 



To return, however, to the table which contains the numbers 

 marked in our third trial, no inference can be drawn from it as to 

 the right shape of the plough's breast, hollow or full, for sandy 

 land ; but, as a proceeding adopted on the next day seems to throw 

 some light on this point, I will mention it here. It occurred to me 

 that there might be a considerable difference in the draught of the 

 plough, independent of the ease with which it severed the ground 

 and threw over the furrow-slice. I accordingly desired each 

 ploughman after ploughing the trial-furrow to pass over a certain 

 space of unploughed ground, when the draught was taken down 

 from the draught-gauge, and the same thing was done on another 

 day by passing the plough along the empty furrow. The draughts 

 of the wheel-ploughs are given below from the first trial as the 

 fairest for them ; those of the STving-ploughs were the same in both 

 cases. I add the weight of the ploughs, taken as nearly as I was 

 able to estimate it with the means in my power. 



