in breadth; and can be removed at pleasure, for the purpose of repairing the fans, by unscrewing the nuts at a and b. The circular space N, O, E, through which the supply of the air to the fans is furnished, is 1 foot 4 inches in diameter. The hopper P rests from C to s, 2 feet along the top of the machine, and is at the extremity of the projection at C 6 inches, and at Q 7 inches above it, measured perpendicularly. The top of the hopper spreads out in length 2 feet 6 inches, and in breadth 2 feet 4 inches. Its bottom descends 4 inches to c below the line of Cs, and at c has a semielliptical hole cut out across its whole breadth. There is also a rectangular hole of about 4 inches high cut out of its front, over which the slide s passes up and down by means of the screw Q, which regulates the quantity of grain emitted from the hopper in the process of cleaning.

The top of the apparatus def fits under the bottom of the hopper, and forms its shoe, which, by operating on the grain through the elliptical hole made there, puts it in motion. This apparatus is suspended by an iron pivot at d, which is placed in a rail fastened across the breadth of the machine there; and its other end is supported by two chains 1 foot & inch long each, hanging from the cross rail G, which connects the top of the standard AB and its fellow; and which are both produced 8 inches above the top of the machine, in order that these chains may have more liberty to oscillate. The frame ef, 1 foot 3 inches long and 41 inches deep, is fastened together transversely by iron rods 1 foot 4 inches in length rivetted at both ends. Into the part corresponding with the dotted line immediately above the letters e and f, are slid the riddles which are used for the sifting of the different kinds of grain. These riddles, made of iron-wire, fastened to a narrow frame of thin iron, are 1 foot 3 inches in length, and nearly 1 foot 4 inches in breadth. That for wheat contains 4 squares in the length of an inch; for barley, 3 squares; for oats 25 squares; and that for roughs, as the roughest uncleaned grain is termed, a square of 1 inch to the side.

The riddle is moved by a small iron rod u y, Fig. 2, 3 feet 8 inches in length, fastened at one end, which is eyed, by a nut which screws into a crank, fastened on the end of the fan axle opposite to that of the pinion N. This crank must not exceed 2 inches in play. The other end of the rod, which is also eyed, is

fastened by a nut to the under army of the crank w v. A piece of leather, placed on each side of the eyes of the rod, softens the noise of the machine very much. The other arm a is fastened by two intermediate joints to a jointed staple in the frame ef, through a hole in the lining of the machine. These arms are 21 inches long, and set at right angles to each other, and also at right angles to the shank of the crank w v, which is 9 inches long, and which at v performs a quadrantal motion in a socket, and at w through the staple.

The grain falls upon the inclined plane hm, the upper part of which, hi, 1 foot long, is made of sheet iron, and slides up and down at pleasure. From i to m is of deal nailed firmly, with the exception of the part from k to l, which forms a screen of wire-gauze 8 squares to an inch in length, stretched on a frame of wood, and nailed with tacks through a selvage of tin. This screen permits all the dry earth, sand, or seeds of wild plants which may have been in the grain to pass through. no is a board 2 feet long, which moves up and down at pleasure, and is kept in its place by a wooden catch on the cross bar at H. The chaff is blown over the top of this board at n, and falls down beyond B. The light corn falls over h, and down below o, while the clean grain slides down h m to m.

The space between the standard AB and its opposite fellow, is lined up with deal, 2 feet 3 inches, as far up as H, to keep the chaff and light corn separate. The top of the machine is covered in front of the hopper P, as far as to g, 1 foot 1 inch. The coom is continued as far round as from b to d above, and I tor below, the current of air passing up in the direction of the arrows at k and i, p and q form two handles, by which two females can lift the whole machine anywhere with great ease. To save the inside of the lining where the frame e f beats against it, it is necessary to place a stout piece of plate iron around the point of contact on each side; and it must be fastened with screw nails, as the constant beating will soon start common nails. It is recommended, not to use any oil, because the dust of the barn soon forms a paste with it, which will clog the motion of the machine. The gudgeons should rather be turned smooth on a lathe at first. The peculiarities which are apparent in the construction of the machine described above, consist in placing the standards at

an angle to each other, the distance between A and C being only 3 feet 4 inches, whereas the distance between B and D is increased to 5 feet 2 inches, and which is produced 4 inches more to m; by this arrangement, the part m, at which the clean grain issues out, is placed more prominently, and of course more conveniently, for the person who takes away the grain to be riddled. This arrangement, too, obviously increases considerably the length of the inclined plane h m, and of the wiregauze screen k l, over both of which the grain slides in its descent to m, and through the latter of which it deposites any sand, earth, or small seeds of wild plants which are mixed with it, and even any shrivelled light corn that may have escaped the force of the wind. It also lowers the angle of the inclined plane to 32° instead of 45°, by which the grain, in descending, gets more time to deposite its impurities. The coom K is by this arrangement placed a little more out of the way of the person's head, who takes away the grain. The large wheel L is also an improvement. The pinion N, upon which it operates, makes fully five revolutions for one of the large wheel, and as in ordinary cases the latter only requires to make twenty-eight revolutions in a minute, the fans O will therefore make 144 in the same time. This easy motion to the driver of the wheel, for which a woman has sufficient strength, thus generates an immense current of air by the rapid motion of the fans. This current, though amply filling the place from d to r, 2 feet, is forced in the direction of the arrows, through the riddle, and of course between the grains of corn which are at the same time passing through it, and makes its escape by an aperture of only 10 inches from fto g, the width of the machine between the linings being only 1 foot 8 inches.. To facilitate still farther the driving of the machine, it is necessary to make the shank of the handle M 91 inches long, and which, as a radius, will be found to describe a circle round the axle of the wheel, the most convenient in size for the easy motion of the body of the driver. The slide s should only be elevated above the bottom of the hopper 1 inch, and in order to make the emission of the grain from it more complete, the hopper should always be amply supplied with corn. Many contrivances have been adopted by introducing pinions and shafts and rollers, pitch wheels and pitch chains, and sheaves

and belts, to shake the riddle, and supply the corn regularly to it from the hopper, in order to supersede the use of the old spear and crank and shoe, as described above. These contrivances have no doubt to a certain degree succeeded. But none of them can supply the grain more regularly, or imitate the vibratory motion of the human hand in riddling so well, as the combined motion arising from the simultaneous action of the loose spear and crank, the quick oscillations of the long chains g, the sort of undulating vermicular motion of the shoe d at the pivot, and the five gentle beats of the riddle frame e ƒ against the lining of the machine, to one turn of the large wheel; while any set of these other contrivances imposes a considerable additional weight for the driver to overcome.

S.

ON PRUNING FOREST-TREES. By Mr GAVIN CREE, Nurseryman, Biggar.

To its woods a country owes much of its beauty; they temper the severity of the climate for the benefit both of the flocks and the crops of the husbandman. But in a no less important point are woods to be viewed, from their economic value. As timber they are extensively, nay universally, employed in all the mechanical arts; and hence the proprietor of woods has to look to them not only as an interesting but as a highly valuable species of property.

Woods are so extensively grown, that there are few landed properties, however small they may be, where they are not to be found to a greater or less extent, either planted by the hand of man, or the spontaneous production of nature. And as it must be obvious that a vast body of people, either as proprietors or as having woods under their charge, must feel an interest in the proper mode of management of this species of property, I trust that you will readily give a place to the following observations on one of the principal subdivisions of this extensive subject-Pruning. That the management of woods is not well understood, or at least but imperfectly attended to, and therefore that the remarks which I am about to state are not

uncalled for, may readily be admitted, if we may be allowed to judge from the present state in which a great majority of woods are to be found. I am sure, indeed, that any person of ordinary observation will agree with me in saying, that the mode of management bestowed upon woods in most places, is far behind its sister art,—the agricultural operations of the field. But we ought always to keep in mind, that a mismanaged crop of wood is a very different thing from a mismanaged crop of corn. The latter is only an annual crop, and hence, however much a farmer may feel for the failure of any of his crops through carelessness or mismanagement, the loss is only that of a single season; whereas a mismanaged crop of wood is, comparatively speaking, the loss of the land itself, the crop requiring frequently half a century, and sometimes more, to arrive at maturity. But it is much easier to admit that the evil of mismanagement of our woods does exist, than to explain the reasons of that carelessness or indifference towards this species of property, on the part of those to whom, under proper management, it would become such a source of profit.

The young and rising tree must be modified by art; for though nature performs her work unassisted and alone, she is often found to produce irregularities in the growth to maturity of a tree, which are not profitable, nor suited to the uses to which it is employed by man: hence it is for man to modify the tree, so as to suit the purposes required.

Much discrepancy exists in the statements of different authors on the subject of pruning. Pontey, Nicol, Sang, Monteath, and others, as is well known, hold very different opinions on many points connected with it. In such circumstances, those who have the charge of woods, and who may be more guided by the opinions of others than from rules deduced from their own experience, may feel a difficulty in determining the proper system which ought to be adopted. Besides, it is not to be expected that foresters in general, and quiet country gentlemen, should have in their possession the works of many authors on this subject, to enable them to contrast and collate the different modes recommended, and to weigh their merits, or ascertain their correctness, by long-tried experiments. Hence it is that

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