ON{THE PLOUGH. 29

From the preceeding reafoning it appears what form of the plough is moft advanta-_ geous, fuppofing it a half-wedge, and that its properties are to be determined from the_ theory ofthatinftrument. But perhaps it may be afked, whether this is the beft figure, and whether fome other might not be attend- ed with greater advantages? A fufpicion that this might be the cafe, feems to have given rifeto the curved mould-board, which has already been defcribed.

The figure of a thip has alfo been quo- ted, and an analogy apprehended or i“ magined between the motion of it and that of the plough. It has been fuppofed, that earth in a ftate of perfe&t cultivation ap- proaches the nature of a fluid, and that the figure moft proper for moving through wa- ter, istherefore beft adapted for moving through foil.

It is evident, from what was formerly ob- ferved concerning the direftion of the force that pulls the plough, that the refemblance to the figure of a fhip can only take place on the right fide; and that the left fide mutft infallibly be plain, becaufe in this form on-

ly