ae is

THE DRILL PLOUGH. 693

the top, to prevent with certainty any of the grain from fticking in them, as they revolve.

Fourtbly. À fcrew of iron about three inches long, with a fquare head to receive a{crew-driver, is to pafs through the end A of the tin cylinder on one fide of the axis, as at x, Fig. 4. The fcrew part of this is to lie in a hollow groove of the wooden cylinder, and to be received into a put, or female fcrew, which 1s fixed to the wooden cylinder. The head part of the fcrew, which pañles through the end A of the tin cylinder at x, muft have a fhoulder within the tin cy- linder, that it may not come forwards through the end ofit; and a brafs rirg muft be put over the fquare end of the fcrew on the out- fide of the tin cylinder, with a pin through that fquare end of the

{crew to hold on the brafs ring.

Thus when the fquare head of the fcrew is turned by a fcrew-.

driver, it gradually moves the tin cylinder backwards and forwards one inch on the wooden one, fo as either to prefs the end A of the tin cylinder into contaét with the end of the wooden cylinder within it, or to removeit to the diftance of one inch from it, and leave a void fpace at the end A.

Fifthly. The ends of all the holes of the tin cylinder, which are next to the end A ofit, are now to be enlarged, by flitting the tin three eighths of an inch towards À, on each fide of the hole; and then that part of the tin, included between thefe two flits, which will be half an inch wide, and three eighths of an inch lengthways in re- fpect to the cylinder, is not to be cut out, but to be bent down into the excavations of the wooden cylinder beneath, fo as to lie againft that end of the excavation which is next to A.

But thefe proje“ting bits of tin, before they are bent down into the excavations of the wooden cylinder,. muft be filed a little lefs at the projeting end, which is to be bent down, than at the other end;: as the excavations of the wooden cylinder are to be rather narrower

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