110 Report on Trials of Plows. 



when it projects forward about one-quarter of an inch and is then 

 moulded off to the point o, thereby leaving sufficient shoulder 

 for the hole through which the front bolt is to be fastened. On 

 the face of the mould-board, Fig. 1, the concave surface d to e 

 continues in the same slope to about two-thirds the distance above 

 the neck over the line f c, where it projects forward in a concave 

 sufficiently deep for the reception of the head of the front bolt 

 terminating at the top under the beam in a sharp edge, having 

 the corners rounded off. The back part of this head runs back 

 about one-quarter of an inch beyond the curved line of the back 

 part of the slice, thereb}' leaving space for the insertion of a hole 

 to be cast for the reception of the end of the brace that extends 

 from the heel of the bar to the said hole in the head. This form 

 and arrangement present such a shaped mould or pattern as may 

 be cast at one operation. 



" Fig. 3 is a view of the share where a line from the point a 

 to the point c extends to two and four-eighths inches in length, 

 and a line from c to b is of three and three-eighths inches in length, 

 and the distance c to e is one and five-eighths inches along the bar. 

 The width of the share from e to d is two and three-eighths 

 inches, and the edge from heel to point is sharp throughout. 

 That part between a and / extending in a circular from d to f, 

 and the remainder of the point from f to a, is rounded at the 

 extremity of said point. The depth at c, in Fig. 4, of the bar 

 is to be three-eighths of an inch, and at e it is to be seven-eighths, 

 and extending back to b of the same depth, this share and bar is 

 to be made of wrought iron. These proportions are reduced to 

 one-fourth of a plow of full size, so that in constructing a mould- 

 board of the full size of my ' Smeller Plow ' the proportions are 

 to be increased accordingly." 



It will be observed that Mr. Jacobs' method is wholly empirical, 

 or, at least, if there is a principle involved in its construction, it 

 is not obvious to us after a careful examination, and none is hinted 

 at in the specification. It consists simply of lines drawn in certain 

 directions, and of specified lengths in a plane and from given 

 points in these lines, letting fall perpendiculars of given lengths, 

 which are ordinates to the desired curve at these points; the points 

 of the curve being ascertained in this way, the remainder of the 

 pattern is cut aAvay so as to form a regular curve with them. 



The next attempt to apply mathematical principles to the con- 

 struction of the mould-board was made by Aaron Smith, of 



