44 ADRES ST aa Ve

reafon is, that, by pulling in this manner, their whole force is employed in promoting motion in the direCtion in which them- felves move; whereas, in pulling either up- ward or downward, they ac obliquely to the direction forward’; and confequently part only of their farce can be exerted in that direction; and this part will be pro- portionally fmaller, the more upward they pull. Hence then it follows, as the great- er the inclination of the plough, the more upward always muft the cattle pull, that all the advantage gained by the inclination is loft by the direction of the force, and that, on the whole, no one inclination is prefe- rable to another. The only exception to this general conclufion is the cafe of land in a low ftate of cultivation, infefted with ftrong roots of vegetables, which will flide more readily on the face of the coulter the more

it

allows them to a&t in the moft natural and eafy pofi- tion. Befides, it is the horizontal direction that pro- motes motion forward; for, if they pull upward or downward, a part only of their force can be employ- edin the horizontal direction, as is plain from the refolution of forces,