PLOWS FOR MECHANICAL POWER 177 



inches is provided on the present plows, and practice has shown 

 that gauge wheels should be at least twelve, preferably four- 

 teen or sixteen, inches in diameter. Some allowance must 

 be made for hummocks; hence this construction is apt to limit 

 the depth, except in breaking. If placed far to one side of 

 the beam to secure greater depth, or too far forward in order 

 to clear the coulter, it fails to protect the point of the plow. 

 In the forward position the shortening of the radius between 

 it and the hitch increases the difference in elevation between 

 point and heel of share and causes steps between one furrow 

 and the next. This is generally objected to by prairie farmers, 

 though, as previously noted, a truncated furrow is desired by 

 Scotch farmers as being sharper in outline. A more serious 

 objection is that in the advanced position the wheel exagger- 

 ates irregularities of the surface, and the sole of the furrow is 

 uneven. Moreover, with the added distance between the centre 

 of resistance and the gauge wheel, the pressure of the latter 

 on the ground is greatly increased, together with the draft. 

 On the double-hitch type a fixed gauge wheel is placed be- 

 tween the plows to the side of one point and considerably ahead 

 of the other. While this permits of high lift and deep plowing, 

 it does not offer equal protection to both plows. Not being 

 placed in line between the two centres of resistance, it acts as 

 a fulcrum for two lever arms of unequal length, and subjects 

 the beams to severe twisting strains. On the single-hitch 

 plows a wheel set too far to one side of the landside plane 

 has a similar effect. Granting that the rolling coulter's posi- 

 tion just above and to left of the plow point allows of little 

 variation, the most practical position for the gauge wheel 

 seems to be as little to the right of the centre of resistance as 

 is necessary for clearing the beam in deep plowing, and as nearly 

 opposite the point of the share as will allow trash to pass freely. 

 It has even been suggested that the coulter and depth wheel 

 might be combined to advantage, the former to consist of a 

 sharp flange attached to the side of the wheel, which in this 



