90 MECHANICS. 



plowing. When the furrow is shallow (as shown by the 

 lines G H, fig. 102), tlie centre of resistance will be at A, 

 requiring the team to be fastened to the lower side of the 

 clevis, C ; but when the depth is greater (as shown by F 

 H), the centre of resistance will be at B, requiring a 

 higher attachment to the clevis ; the point of draught, E, 

 remaining the same in both cases. 



So great is the difference between an awkward and skill- 

 ful adjustment of the draught to the plow, that some 

 workmen with a poor implement have succeeded better 

 than others with the best ; and plows of second quality 

 have sometimes, for this reason, been preferred to those 

 of the most perfect construction. 



C0:srBINED DKAUGIIT OP ANIMALS. 



When several animals are combined together, it is of 

 great importance that they should be exactly matched in 

 gait. Much force is -F'g- 103. 



oflen wasted when ^ 1 ^^ 



they draw unsteadily efcHZZZMZI 



or unevenly. It is { 



more difficult to di- 

 vide the draught equally among several animals when 

 placed one before the other, than when arrayed abreast, for 

 some may hang back, and others do more than their share, 

 unless a skillful driver is always on the watch. It also hap- 

 pens, when thus arranged, that the forward horses draw hori- 

 zontally, while the hindmost one draws in a sloping line, 

 and the line of draught between them thus being crooked, 

 more or less force is lost. This may be, however, remedied 

 in part by placing the taller animals forward, and the 

 smaller behind. 



For these reasons, when only three horses are used, they 

 should always be placed abreast. The force required for 

 each may ba rendered exactly equal by the whiifle-trees 



