1 Cla PE 6 est Ae?

fame furface uppermoft, as a common wedge feparates the parts of any body be- tween which it is made to pafs.

The earth now being caifed ups the next ftep is to place it on its edge, or lay it on its back, as fhall be judged moft proper.

Forithis purpofe, the mould-board is gene- rally made fteeper, or lefs loping toward the hinder than the fore-part. But what chietly produces the effect now fpecified is, the rai- fing of the hinder part of it above the level of the fore-part.© By this conftruction the mould-board rifes and projects atthe fame time*. The preflure on the different parts of the earth of the furrow takes place inva correfpondent manner; the loweft parts are leat preffed, the higher ones{till more, ac- cording to their height. It is abundantly plain, that, by this form, the plough muft place the earth on its edge, or turn it more or lefs over, according as the proyeCtion and inclination of this part are greater or lefs; and alfo that the refemblance to the

wedge, * AB, fig. 5- reprefents the furface of the ground

or plane, on pihich the plough moves; BK, the rife and projection of the mould-board above that plane.