I4 Of the Coulter.

of che furrow, are, cach of them, to be kept ſtraight. This circumſtance, as we ſhall ſce more fully afterwards, re- quire that the land ſide and ſole of the plough be plane ſurfaces. The coul- cer therefore muſt be placed in the plane of the land ſide of the plough. By this means, the cut which it makes forms the land ſide of the furrow, to which the plough is afterwards preſled, by the reſiſtance ating upon the fur- row ſide of the ſock and mouldboard. For the ſame reaſon, it appears proper to me, that the land fide of the coulter ſhould be in the plane of the land ſide of the plough, and that its whole thickneſs (houid be on the furrow fide. When the plane of the coulter has any other poſition, there will always be a force

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