Line of Draught of Plows. 175 



no doubt an extreme case — and the usual angle of 20 deg. as a 

 minimum, we can predicate that, at any angle intermediate to 

 lab and / a g^ the resistance can never be reduced to the mini- 

 mum of 407 pounds. Hence it follows, as a corollary, that 

 ivheels placed under the beam can never lessen the resistance of the 

 plow; but, on the contrary, must in all cases increase the resist- 

 ance to the motive force more or less, according to the degree of 

 pressure that is brought to bear, and this will be proportional to 

 the line of the angle in the resultant, a g, of the line of draught. 



We have now finished the discussion of the wheel question on 

 theoretical principles, deeming it best to introduce no disturbing 

 questions to distract the attention of the reader until all that we 

 had to say under that head was brought to a close. 



We may now remark that our theoretical views are based upon 

 a uniform motion, a uniform soil and a homogeneous texture, but 

 such a coincidence of conditions is rarely met with in practice. 

 Some portions of the soil are wet, while others are dry; some 

 parts are hilly, and others level; some parts are adhesive, and 

 others are crumbling; some are stony, others full of roots. The 

 instances are indeed rare where there is a perfect uniformity in 

 the conditions which are essential to bring it into conformity with 

 theory. 



There are few questions connected with plowing which have 

 been more energetically or more persistently disputed than that 

 between wheel and swing plows. The Scotch plowmen have been 

 especially pugnacious, doing battle for the swing plow with the 

 utmost vehemence. The English plowmen have been equally 

 certain that the wheel was essential to good plowing. While the 

 Americans, thinking little about the matter and saying less, have 

 instinctively adopted them. 



The advocates of the swing plow claim the following advan- 

 tages. ^ 



First — It educates a better class of workmen. Almost any 

 one, after the practice of one or two days, can use a wheel plow 

 and do pretty good work. None but a first-class workman can 

 make good work with a swing plow. 



' Second — Its depth can be regulated by the proper adjustment 

 of the whiflie-trees in the clevis, or by increasing the length of 

 the traces. 



Third — The plowman can regulate the action of the point by 

 bearing upon or lifting up the handles. 



