History of the Plow. 



63 



equal parts, 1, 2, 3, 4, etc., and draw the radii, B 1, B2, B3, etc., 

 draw the parallel lines, 1 1', 2 2', 3 3', etc. Draw the share, 

 dfg e, and the lines d e, the neck of the share, and 3' 6', makino- 

 the distance between them equal to the length of the mould- 

 board. DraAv the diagonals G' d, 5' 1', 4' 2' and 3 3'. These lines 

 will represent the twist of the mould-board, the zero being at h. 



Mr. Rham recommends that all plows should be thus made, 

 wath straight transverse lines, but that the vertical lines should 

 be altered to suit different soils. So that, for medium mellow 

 soils, the vertical lines should be straight ; for stiff clays, convex, 

 and for sandy and loose soils, concav^e ; the degree of convexity 

 to be proi3ortioned to the stiffness of the clay, and the degree of 

 concavity to be proportioned to the looseness of the sand. 



Fig. 58 represents these various sections. A B represents the 

 section contiguous to the neck of the share ; C B in the middle 

 of its length, and D B at the heel. No. 2 represents the convex 

 lines for stiff soils, and No. 3 the concave lines for loose soils. 



The tendency of plow-makers since the publication of Mr. 

 Rham's views has been to approximate their mould-boards to the 

 lines indicated by him. 



We give on Plate V figures accurately representing the plows 

 of Mr. Howard and Mr. Ransom, which may be taken as repre- 

 senting the utmost perfection to which the art of plow-making 

 has reached in England up to the present time. 



As the plan of Mr. Rham has been substantially adopted by 

 some of the most eminent plow-makers in England, we Avill give 



