6.‘ANE(SO Sees

an inveftigation of the méchanical principles on which it is conftructed, with a view to determine its beft and moft advantageous form.|

The moft corre&t general idea we can conceive of the plough, or the inftrument in mechanics whofe form and manner of ope- ration it moft nearly refembles, is that of a half-wedge™, abftrating from the beam and handles, which are fubfervient intirely to the purpofes of moving and managing it. This view, indeed, is fo varied and difguifed by a number of circumftances, that the refem- blance may not perhaps immediately appear. It will be proper, however, to keep it in our eye, as the beft ground-work to'which every part of the defcription may be referred: And, when jall deviations are explained and accounted for, the fimilarity will probably be found greater than is expected.

The

# ABC, fig. I. is a whole wedge. Divide the angle at B into two equal parts, by the line BD, which line will bife& the wedge, and point out its direCtion; and confequently DBC. or ABC, fig. IL willbe a half wedge. AB, fig. II. is the flat or left fide; BC is the right or projected fide; AC is the back; and the narrow fide ABC is the edge.

2S