124 Report on Trials of Plows. 



extent of the wing back of the second division, as it may be cut 

 short of, or extended back of the third division; as also with the 

 amount to be cnt away along the lower edge of the wing back of 

 the heel of the mould-board. 



" The drawings represent that form of the auxiliarj^ parts which 

 I prefer, but to which I do not wish to be nuderstood as confining 

 myself. The points where the several lines g f^ to F f^'^ inter- 

 sect the vertical plane of the land side, and marked jj^ to p^"^, in 

 Fig. 5, will give the general configuration of the line of the 

 forward cutting-edge, termed the shin of the plow. The mode 

 of procedure which I have adopted for working out the block of 

 wood to the form required for making a pattern is as follows: 1 

 make an instrument or gauge, Fig. 7, consisting of a plate, q, on 

 a base, r, at right angles therewith, and one edge of the plate, q, 

 is cut to a form fitting the concavity oi the arc, h, Fig. 6, when the 

 base, r, of the said instrument is in the plane of the base of the 

 said Fig. 6. and hence this curved edge will be the proper gauge 

 to determine when the face of the block, Figs. 2 and 3, is cut to 

 the required concavity in the plane of the second division. I 

 transfer on the face of the plate, q, of the said gauge up to the 

 curved edge thereof, the graduations or divisions of the arc, h, 

 Fig. 6. When the plane of the said gauge is in the plane of the 

 second division, B b, and the plane of its base in the plane of the 

 base of the block and the angle, c, at twelve inches from the face, 

 A a, of the said block, or vertical plane of the land side, then 

 the workman has obtained the required concavity of the face of 

 the block in the plane of the second division, and marks thereon 

 the divisions on the face of the gauge to locate the several 

 divisions, numbered from 1 to 12, of Fig. 6. I then make another 

 gauge, Fig. 8, in like manner, with the curved edge thereof fitted 

 to the concavity of the arc k, Fig. 6. While the base of the gauge 

 is in the plane of the base of Fig. 6, and on the face of thisgaugo, 

 I transfer the graduations of the arc k. I then cut into the face 

 of the block, in the direction of the plane of the third division, 

 until the curved edge of the said gauge touches every part of the 

 said surface, and its vertical edge, £J e, is at the same distance 

 from the plane of the block which represents the land side, as the 

 line ^ e, Fig. 6, is from the line A a, of the said figure, and the 

 base of the gauge is in the plane of the base of the block. This 

 determines the requisite concavity of the block in the plane of 

 the third division, and at the re(juircd distance from the land 



