COMBI^-ED DRAUGHT OF ANIMALS. 97 



usually employed for this purpose, and represented in fig. 

 103, where two horses are attaclied to the shorter end, and 



Fig. 104. 



i>r. ^1! ih 



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& 



M 



Whipplc-trec for three horses. 



the third to the longer end of the common bar. Another 

 ingenious but more complex arrangement is shown by fig. 

 104, where also the ^. .. 



central horse has 

 only half the two 

 others, by being at- 

 tached to the longer 

 ends of the inter- 

 mediate bars. An- 

 other, and a more 

 perfect contrivance, 

 is Patterns Three- 

 horse Clevis, re- 

 presented by fig. 105. It consists of two w^lieels to- 

 gether, one twice the diameter of the other, and each 

 having a groove in which a chain runs. The chains 

 are fastened to the respective wheels, so that the 

 "single horse draws on the larger wheel, against the two 

 horses on the smaller. With common w^hiffle-trees, the 

 relative draught of each horse is maintained only w^hen 

 they draw evenly ; with Potter's there is no variation at 

 any time. It is made by E. M. Potter, Kalamazoo, Mich. 

 Fig. lOG represents the mode of attaching four horses in 

 draught, their force being equalized by passing the chain 

 round the wheel in the pulley-block, , security being pro- 

 vided that the liindmost pair shall not encroach on the 



