History of the Plow. 123 



number 4, which will be found to coincide with the diagonal 

 line g f^ and ending with number 12, which in both figures is the 

 IDoint of intersection of the diagonal line Ff^' with the line ^ « 

 or plane of the land side. And the divisions obtained from the 

 arc k or third division, in like manner transfer to the line E e, or 

 third division, on Fig. 4, measuring on both figures fi-om the lines 

 A «, or plane of the land side, and the division number 4 will be 

 found to coincide with the diagonal g f^, and the division num- 

 ber 12 with the diagonal line Ff^'^ or upper edge of the working 

 surface of the mould-board. From the several points of division 

 thus transferred on the lines D d and F e of Fig, 4, except the 

 two numbered 4 and 12, on which the lines Ff^~ and gf^ were 

 previously drawn, I draw straight lines diagonal to the plane of 

 the land side, which lines are marked Ff^ to 11 inclusive. And 

 where these several lines cut the lines B b, or plane of the second 

 division, the distance of each from the line A a, or plane of the 

 land side, will be found, on measurement, to be equal to the dis- 

 tance of the correspondingly numbered divisions on the arc h of 

 the second division from the line A a on diagram Fig. 6. In this 

 way the inclination which the surface of the mould-board makes 

 to the plane of the land side along the several lines gf^ to Ff^' 

 is obtained, defined and proved, and it only remains to olUain, 

 define and prove the inclination of the said surface to the base of 

 the plow along the said lines. This is done by transferrinjx the 

 divisions on the arcs o and k, as projected by lines parallel with 

 the base, to the lines A a and F e. Those on the line A a of 

 F'icr. 6, I transfer to the line D d of Fig-. 5, measurino; both fitjures 

 from the base; and those on line F e of Fig. 6 to the correspond- 

 ing line F e of Fig. 5, measuring both figures from the base. 

 The surface of the mould-board having been defined at the first, 

 second and third divisions, and along the several inclined lines 

 from g f^ to F f^', the workman will be enabled to make the 

 surface between conform properly to the surface at these lines; 

 but it will be obvious that the number of graduations on the arc 

 h of the second division, instead of being made one inch apart, 

 which I have found to be sufllicient in practice, may be made as 

 much less than an inch as the constructor may desire. As the 

 form below the line gf'^ runs into the cutting edge of the share 

 it is left to the judgment of the constructor to determine the 

 form of that part, as also the form or extent of the surface above 

 the line of the ui)per working edge; of the m()ul(l-lK)ard and the 



