( 52) 
able pens ; those of Lord Kaims, of Mr. Young, of 
Mr. Arbuthnot, of Lord Somerville, and of Mes 
sieurs Duhamel, Chateauvieux, Bose, Guillaume, 
&c. It is not for us, therefore, to do more than as- 
semble and present such rules for the construction 
of this instrument, as have most attained the autho- 
rity of maxims. 
Ist. The beam, or that part of the lait which 
carries the coulter, and furnishes the point of draft, 
should be as near that of resistance as possible; be- 
cause the more these are approached, the less is the 
moving power required. Even the shape of the 
beam is not.a matter of indifference. In the old 
ploughs it was generally straight, but a small 
curve is now preferred; because it has the effect of 
strengthening the coulter, by shortening it. 
2d. The head of the plough is the plane on which 
it moves. This should be concave, because that 
form offers fewer points of friction, and, of course; 
less resistance. Between the beam and the head, is 
an angle, on which depends the principal office of 
the plough ; the making, at will, a deep or a shal- 
low furrow. [If you wish a deep furrow, diminish 
the angle, and vice versa: but this angle should, in 
no case, exceed from 18 to 24 degrees. 
The resistance made to the plough being produc- 
ed less by the weight of the earth, than by the co- 
hesion of its parts, it is evident that the head should 
be shod with iron, and rendered as smooth as pos- 
sible. ‘This remark applies equally to the soc and 
to the mouldboard. 
' 8 
