152 



Report on Trials of Plows. 



J^iff. 77. 



with a different velocity the continuity of the \\xvQ,fd will be bro- 

 ken, and a fracture will occur at the point y* represented by b f d, 

 and it is also evident that every successive line of the slice e dfc 

 0^ L will be subject to a similar 



fracture on passing the point 

 \ J f. It is, however, unneces- 

 sary to have so large a frac- 

 ture; as the slightest fissure 

 is all that is required, we 

 may therefore very greatly 

 diminish the angle of the 

 wing with a great saving of ^i'^' 78. 

 the power required, as at Fig. 78, where b f d, the angle of 

 fracture, is seen to be very greatly reduced, although the actual 

 pulverization is quite as well performed as it was with the much 

 larger angle, b f d, in Fig. 77. 



We have now, in addition to the longitudinal fissures shown in 

 Fig. 74, on the sides, a b and c d, another series of transverse 

 fractures across the face, c cZ, Figs. 75 and 77, made by the lines 

 of the plow, which must necessarily break up the slice into fine 

 particles, which will 

 admit air and moist- 

 ure, and facilitate the 

 chemical transforma- 

 tions in the soil which 

 we have shown to bp 

 so essential for the d 

 velopment of its late i t 

 fertility. 



It is shown in the 

 History of the Plow, 

 which we have at- 



T%^ ij- s b 



J^/</' 79. 



tempted to sketch, that the efforts of all the inventors who 

 have applied their skill to the improvement of the moul I- 

 board, have been directed to the formation of a perfectly curved 

 or twisted wedge which should be entirely regular in its foi-in- 

 ation, that is, that the third line should depart from the piano 

 of the second precisely as far as the second does from the 

 plane of the first, and that the fourth should depart from 

 the third precisely as much as the third does from the second, 

 and so on. This is csixMially line <>(' ihe plows which are 



