History of the Plow. 109 



edse of the mould-board will be five-sixteenths inch in len^rth. 

 From the point d to the point b a line is to bo struck of two and 

 three-sixteenth inches in length, and a perpendicular raised frojn 

 the centre of this line to the thin edge of the mould-board will 

 be one-quarter inch in length. The portion of the surface of the 

 mould-board, contained betvveeu each point or extremity of these 

 original straight lines struck as above directed, is to be shaped 

 upon that segment or portiou of a circle as will be between said 

 point having the perpendicular for the height of the arch; the 

 line a h will be the only exception to the rule, and in this particu- 

 lar that three-quarters of the distance across from a towards b will 

 be described on nearly a straight line, the extremity of the point 

 beino; a little elevated. 



" From the point k to the point g in Fig. 2, showing a left hand 

 view of the mould-board, the line between these extremities or 

 points will be of one and three-sixteenth inches in length, and 

 another line from the point/ top' will be two and a half inches in 

 length; the point k is to drop one-eighth of an inch below a hori- 

 zontal line drawn from g towards b. From the point g to b the 

 length of the line will be one and three-sixteenths inch. From 

 the point h to I the length will be one and five-sixteenths of an 

 inch. A perpendicular is let fall from the point a to the hori- 

 zontal plane on which the flat part of the under side of the 

 mould-board rests, designated by the point I, being that of the 

 intersection, and another line at right angles with it, being con- 

 tinued from the point I till it intersects the line running along 

 the face of the slice from k to g, parallel with the bar, at the 

 point j gives a line struck from I to j of three inches in length, 

 which gives the correct width of the board behind from outside 

 to outside. On the back of the inside of the mould-board a flat 

 shoulder is formed of about two inches in length, increasing in 

 thickness of the mould-board towards the upper part to about 

 double the width of the average thickness of the mould-board 

 throughout, and thereby presents a flat surface upon which the 

 right handle is bolted. On the line k g, as a base, a perpendicu- 

 lar is to be raised through / to the point m g two and three- 

 quarter inches in height, and another parallel to it at one inch 

 distant of two and nine-sixteenths of an inch in height. The 

 distance from m to o will be a projection of one-quarter of an 

 inch forwards. The curved line of the front edge of the slice 

 continues its direction beyond /about half the distance on to m, 



