PLO 



PLO 



331 



its progress, the least resistance 

 possible, and consequently to re- 

 quire a minimum in the moving 

 power. Were this its only office 

 the wedge would offer itself as the 

 most eligible form in practice. 

 But the sod is to be turned over 

 also. To do this the one edge of 

 it is not to be raised at all ; for to 

 raise this would be a waste of la- 

 bour. The other edge is to be 

 raised till it passes the perpendicu- 

 lar, that it might fall over of its 

 own weight. And, that this may 

 be done, so as to give also the least 

 resistance, it must be made to rise 

 gradually from the moment the sod 

 is received. The mould-board 

 then, in this second office, operates 

 as a transverse, or rising wedge, 

 the point of which sliding back 

 horizontally on the ground, the 

 other ends continues rising till it 

 passes the perpendicular. Or to 

 vary the point of view, place on 

 the ground a wedge of the breadth 

 of the ploughshare, of its length 

 from the wing backwards, and as 

 high at the heel as it is wide : 

 draw a diagonal on its upper 

 face, from the left angle, at the 

 point, to the right upper angle 

 of the heel : bevil the face from 

 the diagonal to the right bottom 

 edge, which lies on the ground. 

 That half is then evidently in the 

 best form for performing the two 

 offices of raising and turning the 

 sod gradually, and with the least 

 effort; and if you will suppose the 

 same bevil continued across the 

 left side of the diagonal ; that is, 

 if you will suppose a straight line, 

 whose length is at least equal to 

 the breadth of the wedge, applied 



on the face of the first bevil, and 

 moved backwards on it, parallel 

 with itself and with the ends of the 

 wedge, the lower end of the line 

 moving along the right-bottom- 

 edge, a curved plane will be ge- 

 nerated, whose characteristic will 

 be a combination of the principle 

 of the wedge in cross directions, 

 and will give what we seek, the 

 mould-board of least resistance. It 

 offers too this great advantage, that 

 it may be made by the coarsest 

 workman, by a process so exact 

 that its form shall never be varied 

 a single hair's breadth. One tault 

 of all other mould-boards is that, 

 being copied by the eye, no two 

 will be alike. In truth, it is easier 

 to form the mould-board I speak 

 of with precision, than to describe 

 that method either by words or fi- 

 gures." 



To this is appended a more mi- 

 nute description, applicable to 

 drawings, with letters of reference, 

 &ic. — See Domestic Encijclopedia, 

 vol. HI. p. 113., and American 

 Farmer, vol. II. p. 185. 



Robert Smith, of the township of 

 Buckingham, Buck's county, Penn- 

 sylvania, gives the following rules 

 for constructing ploughs. 



" In constructing ploughs, the 

 beam ought to be placed directly 

 over the land side of the plough, 

 so that the cut of the coulter may 

 be square with the cut of the 

 share ; and the land should be 

 given to the plough, between the 

 coulter mortice, and the fore end 

 of the beam : for if the cutting of 

 the share and coulter makes an 

 acute angle with the land, then 

 the plough will incline to fall to 



