170 



Report on Trials of Plows. 



steam or other inanimate power might require it. Neither would 



it be very expedient to adopt a lower angle, since it involves a 



a greater length of trace m 



chains, which at best would 



1)6 rather cumbrous, and it 



would produce a saving of 



force of only 14 pounds on 



the draught of a pair of 



horses. Yet it is worthy of 



being borne in mind that, 



in all cases, there is some 



saving of labor to the horses, 



whenever they are, by any 



means, allowed to draw by 



a chain of increased length, 



provided the clevis of the 



plow is brought into the 



line of the draught, and the 



drauo;ht chains are not of 



such undue weight as to 



produce a sensible curva- 

 ture; in other words, to 



insure the change of angle 



at the horse's shoulder due 



to the increased length of 



the draught chain." 



This subject will be better 



understood when considered 



in connection with Fig. 81. 

 Let a represent the body 



of the plow, b the point of 



the beam, and c the centre 



of resistance of the plow, 



which may be assumed at a 



aeight of two inches above 



the plane of the sole, d e, 



though it is liable to change 



within short limits. The av- 

 erage leno-th of the draught 



chains or traces being ten 



feetjincludingcvener, whiffle i^^/^. cV/. 



