Book IV. 



THRESHING MACHINES. 



437 



so that the lazy horse must cither 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 



'Vn 



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 



400 



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 fairly, or 

 equally, on their shoulders, without twisting their bodies 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 the circle in which he walks, or the chain next to the centre of the walk be 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 equally on his shoulders 

 when pulling, which of course must be less severe on the animal when walking in a circle. 

 2787. 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 follows :^ 



1st, The very great comparative ease obtained for the cattle, in this the heaviest part of their work. 

 This, without doubt, is a real saving of labour ; for it is no exaggeration to affirm, that five horses, yoked 

 by this apparatus to a threshing machine, will perform with equal ease the labour of six horses, of equal 

 strength and weight, yoked in the common way, each horse being independent of the rest 



2dly, A very great saving results in the tear and wear of the machine, from the regularity and urn- 



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