26 



Report on Trials of Plows. 



Ta 



Tl 



have assumed to be six inches), the earth, when the soil was 

 friable and sandy, would rise up over the edge of the mould- 

 board like waves, and fill the furrow behind the plow. It will 

 be seen, however, since in the progress of discovery we have 

 obtained a much better form of mould-board, there is no necessity 

 for this great excess of height. The line a d \s taken at thirteen 

 and a half inches, because in his opinion it was essential for the 

 rear end of the mould-board to project four and a half inches 



beyond the perpendicular, in order to 

 make the sod fall on to the preceding 

 slice by its own gravity. It is possible 

 that this amount of inclination from the 

 perpendicular would be sufficient to 

 efiect the object on level land, but it 

 requires a much greater lateral projec 

 tion to make the sod fall properly 

 when the furrow is turned up hill. Mr. 

 Jefferson's line of inclination is twenty 

 and one-half degrees; modern practice, 

 founded on the necessity of the case, 

 ^ gives an inclination not less than fort}'- 





J^/ff. 20. 



five degrees. 



A block having a transverse section, 

 as in Fig. 19, and three feet long, is 

 taken and smoothly planed on all its 

 sides. This block is represented in 

 Fig. 20. The first operation consists 

 in forming the tail, by which the mould- 

 board is affixed to the stilt or handle, 

 by sawing across from a to 5, on ifs 

 left side, and at the distance of twelve 

 inches from the end, f g ; continue the cut perpendicularly along 

 a e, until the edge of the saw comes to a line one and a half 

 inches above the side n i; then taking h i, j h, each equal to one 

 and a half inches, and saw across the line j k, along the line k e, 

 parallel to the right side. The piece b a e I- j f g will fall of 

 itself and leave the tail, k e d i h j, an inch and a half in thick- 

 ness. It is of the anterior part, b a e d I m n, that the mould- 

 board must be formed. 



By means of a square, trace out on all the faces of the block, 

 lines at an inch distance from each other, of which there will 



