404 



SCIENCE OF AGRICULTURE. 



Part II. 



immediately the other presses the collar to his shoulders. For instance, if the horse yoked 

 to the chains at one arm {fig. 347 a.) were to relax, then the one yoked at the other (/>) 

 would instantly take up his rope, and pull the collar hard to his shoulders, so that the 

 lazy horse must either exert himself, or be drawn backward ; until the hooks, to which 

 he is yoked, rest on the limbers. Thus each horse spurs up his fellow, they being 

 both connected by the ropes and sheeves ; their exertions are united, so as to form one 



power applied to the machine, instead of two powers, independent of one another. By 

 this means, the draught will always press the collars equally upon the horses' shoulders, 

 and though they are working in a circle, yet the strains of the draught must press fair, 

 or equal, on their shoulders, without twisting their body to either side. This advantage 

 cannot be obtained in the common way of yoking horses in a threshing machine, unless 

 the draught-chains on each side of the horse be made in exact proportion in length to 

 the diameter of thp circle in which he walks, or the chain next to the centre of the 

 walk made a little shorter than the one farthest from it, which is often neglected ; but 

 in this way of yoking the horses, the strain of the draught will naturally press equal on 

 his shoulders when pulling, which of course must be less severe on the animal when 

 walking in a circle. 



2639. The advantages of this method of yoking horses to a threshing machine, which 

 was invented by Walter Samuel, blacksmith at Niddry, in the county of Linlithgow, have 

 been fully ascertained by experience, and acknowledged by the most intelligent farmers 

 in Scotland. They are as follow : 



