History of the Plow. 119 



breadth of the intended plow at the heel, c, of the mould-l)oard, 

 say twelve inches, the product of which will be twenty-four inches 

 and one twelfth (24yL)) and add to this product one-tenth thereof, 

 which will make the distance of the point from the line B h 

 twenty-six inches and fifty-nine one hundred and twentieths (-/./g). 



" Having determined the above proportions, I build up a block, 

 represented at Figs. 2 and 3, from which to form the pattern, and 

 consistinor of a series of flat blocks of wood, fflued tosrether to 

 the required height in the usual manner of preparing blocks for 

 making plow patterns. 



" The face, A a, of the said block is made perpendicular to the 

 base and corresponds to the line A a or land side of diagram 

 Fig. 1; the end, E e., presents a plane perpendicular to the base 

 and at right angles to the face, A a, and corresponding with the 

 line E e, of diagram Fig. 1, and the opposite end at g is cut to 

 the required length for the location of the point of the plow. 

 On the under side or face of this block I transfer the two lines 

 B h and D d and the diagonal line Ffivom. diagram Fig. 1, as 

 represented in the dotted lines. Fig. 3. And I also mark on the 

 face, A «, and also on the opposite face of the said black lines, 

 B b and D d to represent the planes of the said lines perpen- 

 dicular to the base, as represented by dotted lines in Fig. 2. 



"I divide the block into three imaginary divisions by three 

 imaginary planes perpendicular to the base, and corresponding 

 with the three lines B b, D d and E e, the first division being at 

 the line D d, the second at the line B b, and passing through the 

 heel of the intended mould-board, and the third at the line E e; 

 I then draw a diagram. Fig. 6, with a base line representing 

 the base of the plow on which I erect a perpendicular line. A; a 

 representing the land side or line A «, diagram Fig. 1, and parallel 

 therewith, and at a distance therefrom of equal to the breadth of 

 the plow from the heel of the mould-board, in this case twelve 

 inches, draw line B corresponding with the line B b on diagram 

 Fig. 1, and from the base mark on the said line twelve divisions 

 of one inch each, numbered from one to twelve. And I then 

 strike the arc of a circle, h, on a radius of double the breadth of 

 the intended plow at the heel of the mould-board, which in this 

 case will be twenty-four inches, the said arc being made to inter- 

 sect the line B b at the base and at the twelfth division from the 

 base; and then draw lines parallel with the base through each of 

 the points of the twelve divisions to intersect or cut the said arc, 



