_A coulter._ Some plows have a straight knife-like coulter (Fig. 52) which is fastened to the beam just in front of the mouldboard and serves to cut the furrow slice from the land. In some plows this is replaced by an upward projection of the share; this is wide at the back and sharp in front and is called the shin of the plow from its resemblance to the shin bone. The coulter is sometimes made in the form of a sharp, revolving disk (Fig. 53), called a rolling coulter. This form is very useful in sod ground and in turning under vines and tall weeds. It also lessens the draft of the plow. _A jointer_ or skimmer which skims stubble and grass from the surface of the soil and throws them into the bottom of the furrow where they are completely covered. The jointer helps also to pulverize the soil. _A truck_ or wheel, attached under the end of the beam. This truck makes the plow run steadier. This is sometimes used to make the plow run shallower by setting it low down. This is not right, for it then acts as a brake and makes the plow draw harder. The depth of the furrow should be adjusted at the clevis. A plow not only has parts but it has character also. CHARACTERISTICS OF A GOOD PLOW A good plow should be strong in build and light in weight. The draft should be as light as possible. The plow should run steadily. A good plow should not only turn the soil but should pulverize it as well. When plowing, the team should be hitched to the plow with as short traces as possible, and the plow should be so adjusted that it will cut furrows of the required width and thickness with the least possible draft on the team and the least exertion on the part of the plowman. THE FURROW SLICE In plowing, the furrow slice may be cut thin and wide and be turned over flat. This method is adapted to breaking new land and heavy sod land. It may be cut thick and narrow and be turned up on edge. Or it may be cut of such a width and depth that the plow will turn it at an angle of about forty-five degrees. By this last method the greatest amount of soil can be turned at least expense of labor; the furrow slice can be more thoroughly broken; the greatest surface is exposed to the action of the air, and plant food is more evenly distributed through the soil. HOW DEEP SHALL WE PLOW? We learned in a previous chapter that the roots of farm plants develop largely in that part of the soil which is worked by the plow; therefore, to have as much tilled soil as possible for root growth, we should generally plow as deep as possible without turning too much of the subsoil to the surface. Lands that have been plowed deep should be deepened gradually by plowing up a half-inch to an inch of subsoil each year until the plow reaches a depth of at least nine or ten inches.