242 Experimental Inquiry on Draught in Ploughing. 



whatever the pace may be ; we have also the plough nibbing against 

 the earth on the land side^ and the furrow^slice rubbing strongly 

 against the mould-board ; all these parts of the draught coming 

 under the head of friction which may not be increased by increase 

 of speed. There is indeed the earth to be raised and thrown 

 asidC;, the labour of which must be increased exactly in the same 

 proportion with the quantity to be so moved ; and consequently 

 with the speed. But there is one other part of the force to be 

 exerted by the plough which we must not overlook, the cutting or 

 splitting force of the share and the coulter ; for this part of the 

 draught may not only not be increased by increased speed, but 

 may even reasonably be supposed to be diminished; since, in 

 operations of the same nature, we see at once that if a spade or a 

 pickaxe were to be used gently and slowly, much more force would 

 in the end be required than with a brisk effort and a quick tap. 



But whatever may be the cause, it is certain that in this first 

 experiment the draught of the ploughs was scarcely raised by 

 doubling the pace of the horses. I determined, therefore, to make 

 a second trial upon different ground, and thinking that this prin- 

 ciple might in some degree serve to account for the greater quan- 

 tity of land which the Scotch horses are able to plough, I re- 

 quested Mr. Morton to observe the pace of those horses when 

 ploughing at Whitfield. He informed me that they plough at the 

 rate of two miles and three quarters an hour, excluding stop- 

 pages, and that in drawing carts singly their walk is at the rate of 

 three miles and a quarter. 



In making the experiment I did not choose the ground, but 

 took a team at work among others, with Hart's plough, on a clover 

 ley. The ground certainly appeared unfavourable for speed, as 

 it was an adhesive loam upon stone brash, in so bad a state for 

 working that the polished mould-board was completely encrusted 

 with earth. I measured out, however, 110 yards, or one-sixteenth 

 part of a mile, by the side of the furrow, and observed, with a 

 stop-watch, the time employed in passing over that space. The 

 teams of three horses were going slowly, at a depth of 4 inches 

 only by 9 in width, but I desired the ploughman to pass along 

 the furrow still more slowly, at the usual rate of going upon heavy, 

 and sometimes, I must say, even upon light land in this neigh- 

 bourhood. At this pace he ploughed the 110 yards in 2 minutes 

 and 40 seconds, being at the rate of 1 J miles in the hour. The 

 draught-gauge marked 23 stone. 



I then desired him to return to the pace at which I had found 

 his and the other teams working ; he now ploughed the 110 yards 

 in 2 minutes and 25 seconds, being at the improved rate of If 

 miles in the hour. The draught -gauge still marked 23 stone, as 

 before. 



