PRINCIPLES OF DRAUGHT APPLIED TO PLOWS. 



95 



Fi-. 101. 



the reason that a great saving of strength results from the 

 use of short traces m plowing. An experiment was tried 

 for the purpose of testing this reasoning ; first, with traces 

 of such length that the horses' shoulders were about ten 

 feet from the point of the plow ; and secondly, with the 

 distance increased to about fifteen feet. With the short 

 traces a strength was required equal to 2^ cwt., but with 

 the long traces it amounted to 3-|- cwt. 



But the draught-traces may be made too short. When 

 this is the case, the 

 plow is necessarily 

 thrown too much upon 

 its jDoint, to keep it 

 from flying out of the 

 ground, by which means it v/orks badly in turning the fur- 

 row. In addition to this evil, the plowman is compelled to 

 bear down heavily, adding to the friction of the sole on 

 the bottom of the furrow, and greatly increasing his labor. 



The line of draught should bo so adjusted that the plow 

 may press equally all along on its sole or bottom, which 

 will cause it to run evenly and with a steady motion. 



Fig. 10 :. 



Line of draught for the ploto. 



This end will be effected by giving the traces or draught- 

 chain just such a length that the share of the plow (or 

 centre of resistance), the clevis, and the point of draught 

 at the horses' shoulders (or the ring of the ox-yoke) shall 

 all form a straight line. This is shown in the annexed 

 figure, where A is the place of the ox-ring or of the for- 

 ward extremity of the traces (fig. 101). 



The centre of resistance will vary with the depth of 



