Bijoii IV. WHEEL PLOUGHS. 399 



wheel (d) placed behind the sole, which, besides considerably reducing the weight 



of draught, is found 



to give a degree of'^^^^i;;^ 



steadiness seldom ex- nN. 



ceeded in the use of n^s^^^ 



the common plough, ^S^\^^ -^"'~~\ '^^^'^' Z^ ~~ i Tt -' 



except when quite ^ I^-^^^^'*!!)*^ 



new, or recently re- vT^^^yt T^. \\ ---''' 



paired with a new \/^^V^^^Ni^\^gA^ 



sock and sole-shoe. ^C_ l^^^^I^^^^ 



At that period, when " ^g ^ 



the back end of the 



sole is quite full and square, the common plough (when well constructed) goes as well as can 

 be wished for ; but, by the great friction of the sole, the back end of it soon becomes convex, 

 and, consequently, the plough loses the steady support of the extremity of the heel ; or, 

 in other words, in proportion as the sole becomes more convex, the fulcrum of the lever 

 is extended considerably forward, so as to be too near the centre of gravity. When that 

 is the case, the least obstruction at the point of the share hrows the plough out of the 

 ground. In order to remedy or counteract that tendency, the ploughman is obliged to 

 raise the point of draught at the end of the beam ; but this expedient, although it gives 

 the plough more hold by the point of the share, is attended with another inconvenience 

 fully as bad as the former ; for, when the point of the share meets with an obstruction as 

 before noticed, the heel of the plough is raised, on account of the point of draught being 

 fixed above the direct line of traction. Thus, the common plough, when the sole becomes 

 convex, is made to go very unsteadily, and often requires the utmost attention and exertions 

 of the ploughman to direct it. What is stated above, however, can only apply to the 

 common plough when out of order by the sole becoming convex. 



2635. Placing the wheel. In order to understand in what manner the wheel ought to be placed so as 

 to reduce the friction, it may be necessary to remark that one of the first properties of a plough is to 

 be constructed in such a manner as to swim fair on the sole. This depends principally on the form of 

 the sole, and position or inclination of the point of the sock, together with the point of draught at the 

 end of the beam (). If these are properly adjusted, the pressure or friction of the sole will be uniform 

 from the point of the share (6) to the back end of the heel [d) ; or, in other words, the friction will be 

 balanced between these two points by means of the beam {a) acting as a lever, the heel {d) being the 

 fulcrum, and a point over the share (c) the centre of gravity. 



2fi36. The centre of gravity or of resistance will be extended nearer to the point of the share (5), in 

 proportion as the soil has acquired a greater degree of cohesion ; as in old pasture ground, or strong 

 clays. But, wherever the point of resistance meets, it is evident that the point of draught at the end 

 of the beam must be placed so as to balance the friction of the sole between its extreme points {b and a). 

 Viewing the machine, therefore (with regard to the friction of the sole), merely as a sledge carrying a 

 considerable weight, by which it is pressed equally to the bottom of the furrow at the extreme points 

 [b and rf), it is clear that, by substituting a wheel at the one point (rf), the one half of the friction of 

 the sole will be thrown on the wheel. The draught is reduced by the wheel from forty to sixty- 

 six pounds, or from one seventh to one fifth (two hundred and eighty pounds being the power of 

 one horse.) 



2637. Wilkies improved friction-wheel plough for two horses (fig- 312.) was invented by 

 the late Mr. Wilkie in 1825, and is manufactured by his son at Uddingston, near 

 Glasgow. We consider this as by far the most perfect implement of the plough kind 

 that has hitherto been produced. The wheel (a) is placed so as to incline from the 



perpendicular, at an angle 

 ^12 ^^^;^^^=^ of about 30 degrees ; and, 



following in the angle of 

 the furrow cut by the coul- 

 ter and share, it ensures a 

 greater degree of steadiness 

 in the motion of the plough 

 than when rolling only on 

 the bottom of the furrow. 

 The sock or share is of cast-iron, which is a great saving both in first cost and repairs ; 

 costing only one shilling, and ploughing at an average upwards of ten acres. Only the 

 coulter requires to be taken to the smithy, the share being renewed by the ploughman at 

 pleasure. The wheel, which is of cast-iron, will last many years. The draught of this 

 plough has been proved at a public ploughing match, in 1 829, to be fully 30 per cent less 

 than that of the common scoring plough of the most improved form. The price is also 

 lower than that of any iron plough now in use. Mr. W. has lately made some of these 

 ploughs with a piece of mechanism attached to the wheel, by the revolution of which, 

 the quantity of ground passed over by the plough maybe indicated. {Gard. Mag. 

 vol. v.) 



2638. The paring wheel plough is of various forms, though it is an implement seldom 

 required. It is used for paring the surface of old grass lands, or leys on clay 

 soil, where the turf is to be burned. A variety in use in the fen districts (^5. 313.), 



