PRINCIPLES OF DRAUGHT. 



119 



which will cause it to run evenly and with a steady mo- 

 tion. 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- 

 A^.-' ward extremity of 

 the traces {Figure 

 92). 



The centre of re- 

 sistance will vary with the depth of plowing. When 

 the furrow is shallow (as shown by the lines G H, Fig. 

 93), the centre of resistance will be at A, requiring the 



Fig. 93. 



Fig. 92. 



Line of draught for the plow. 



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 at- 

 tachment to the clevis; the point of draught, E, re- 

 maining the same in both cases. 



So great is the difference between an awkward and 

 skillful adjustment of the draught to the plow, that 

 some workmen with a poor instrument 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. 



