on the wooden cylinder, are now to be excavated precisely 3-eighths of an inch in depth, to which are to be added 3-eighths of an inch at that end of each of them which is nearest to A; so that, when the wooden cylinder is again replaced in the tin cylinder as before, with one inch of void space at its closed extremity, the excavations in the former will be 3-eighths of an inch longer than the perforations over them in the latter. These excavations in the wooden cylinder should, likewise, be somewhat narrower at the bottom, effectually to prevent any of the grain from sticking in them, while revolving.
4. An iron screw, about three inches in length, with a square head for the reception of a screw-driver, should be passed through the end A, of the tin cylinder on one side of the axis, as at C, in Fig. 4. The screwing part of this must lie in a hollow groove of the wooden cylinder, and be received into a nut, or female screw, fixed to the same cylinder. The head of the screw, passing through the end A, of the tin cylinder at C, should have a shoulder within the tin cylinder, to prevent it from penetrating through the end of it. A brass ring should also be put over the square end of the screw, on the outside of the tin cylinder, through which end a pin ought to pass, in order to keep the ring steady. Thus, when the square head is turned by a screw-driver, it gradually moves the tin cylinder one inch backwards and forwards on that of wood; so as either to press the end A of the tin cylinder into contact with that of the wooden cylinder within it, or to remove it to the distance of one inch, and leave a void space at the end A.
5. The ends of all the holes of the tin cylinder are next to be enlarged, by slitting the tin 3-eighths of an inch towards A, on each side of the hole; that part, however, of the tin included between these two slits (which will be half an inch wide, and 3-eighths of an inch in length, with respect to the cylinder), is not to be cut out, but bent down into the excavations of the wooden cylinder beneath, so as to lie against that end which is nearest to it.—But, before these pieces of tin are bent down, as just described, they should be filed somewhat smaller at the projecting than at the other end; because the excavations of the wooden cylinder are to be rather narrower at the bottom than at the top; and these pieces of tin, when bent down, ought to fit them exactly.
Lastly, When all these holes are thus enlarged, and the bits of tin filed somewhat narrow at their projecting ends, and then bent down into the excavations of the wooden cylinder, the other end of the tin cylinder, with its square socket, may be soldered on. Thus, when the end of the tin cylinder at A, is pressed forwards upon the wooden one towards B, by turning the screw at C, above described, all the excavations of the wooden cylinder will be gradually lessened, and at length entirely closed; by which means they may be adapted for the reception and delivering of seeds of any size, from horse-beans and peas to wheat, barley, and turnip-seed, with the utmost accuracy, so as to sow 4, 5, or 6 pecks per acre, or more or less, at the pleasure of the cultivator, merely by turning the screw a few revolutions, in either direction.
In farther illustration of these
