62 



Report on Trials of Flows. 



were made in moulding and casting, it became possible to make 

 the whole plow of cast iron, so that when a farmer once had a 

 plow that exactly suited him, it could be accurately and certainly 

 reproduced, and multiplied to any extent, at a very small cost. 

 The next step, after the adoption of the sole shoe, was to make 

 the entire frame of iron. They were so constructed that all 

 parts — the handles, beams and shares, the sole, the mould-board 

 and the braces — could be screwed upon with a much greater firm- 

 ness and much greater capability of adjustment than had ever 

 been attained before. Sketches of three of these frames are 

 given in Fig. 55. 



The following figure (56) will show how the mould-board and 

 share was attached to the frame. 



J^/f/. 66. 



The plow made entirely of cast iron was introduced about the 

 year 1800, and l)y 1810 was in very common use. The changes 

 made in the plow for the next quarter of a century were very 

 slight, and these were mainly in the adaptation of the mould- 

 board to different kinds of soil, that is to say, concave vertical 

 lines were adopted in loose sandy soils ; straight lines in medium 

 mellow soils, and convex lines in hard clay and other stift' soils. 



About the year 1840, Rev. W. L. Eham developed the doctrine 

 that the transverse lines of the plo^v should be straight ; and so 

 far as we know, he was the first one who taught this rule in 

 Europe, though he had been anticipated many years in this 

 country. 



Let ABC, Fig. 57, represent the breadth of the furrow. On 

 this diameter describe the semicircle, A 4 C, and divide it into 



