SIEVE. An instrument for separating the smaller of substances from the grosser; they are made of various forms and sizes, to suit the article to be sifted. In its most usual form it consists of a hoop, from 2 to 6 inches in depth, forming a fiat cylinder and having its bottom constituted of coarse or fine hair, canvass, muslin, ;awn, net-work, or wire, stretched tightly over, to the use intended.
There is a kind of sieve in extensive use amoogst druggists, drysalters, and confectioners, termed a drum-sieve, owing to its form, and is used for sifting very fine powders. It consists of 'three parts or sections ; the top and bottom sections of which are covered with parchment or leather, and fit over and under a sieve of the usual form, which is placed between them. Being thus closed in, the operator is not annoyed by the clouds of powder which would otherwise be produced by the agitation, and the material under operation is thus saved from waste.
The sifting process is, however, extremely slow and labo rious. To obviate these defects, the editor, some years ago, devised another form to the apparatus, which is much leas expensive in construction, and far more durable and effective. Annexed is a description. Fig. 1 represents a hollow cylinder, the exterior of which is formed of fine muslin or lawn; two wooden sheaves or discs D D, grooved at their edges, and about six or seven inches in diameter, are fitted to a central spindle, the extremities of which turn in bearings made on the opposite ed es of a stout box, which is shown opened in Pig. 2 (on t owing page); the lid being the same dimensions exactly e other part, so that they may both lie fiat and equally supported when open ; one extremity of the axis is provided with a cross handle E, by which the cylinder is agitated by a backward and forward semi-rotative motion ; the cross also serving as a foot or stand for the cylinder, as shown in Fly. 1. To form the cylindrical cage, two or three stout rings of wire C C are made of the same size as the discs, to which they are connected by annealed wire, running longitudinally from end to end of the cylinder, where the annealed wire is turned round the beads of screws, and thus rettmeini fkom end to end alter- .
nately, until the cage or skeleton is completely formed, which is now ready to receive the required covering of lawn or muslin. This is of course prepared as a bag, with a close seam, but open at each end, and of exactly corresponding with those of the cylinder, so that the covering may be stretched out smoothly, in drawing it over the cylinder. The next point is to . fasten it down, which done by drawing cords with slip knots over the end% in such manner that the cords enter the grooves of the discs ; tbui, by tying down the two outride cords first, and the inner ones afterwards, it is very easily made " as tight as a drum." The pulverised matter to be sifted is then put into the cylinder by means of a figinel E, which is afterwards removed, and the bole stopped by a bung 0. The cylinder is next placed in the box, as seen ist Ilg. 2, and the lid being shut down, the handle is worked by the semi-rotative motion before noticed, which throws continually the whole contents of the cylinder over ib entire circumference, and separates the fine powder from the grosser particles with a rapidity which will surprise the operator, the effect being so much more considerable than by the usual apparatus. When one batch In the cylinder is sifted, the gross matter is emptied out by withdrawing the bung, and giving the cylinder a shake, with the handle upwards ; the cylinder being charged again, the sifting is renewed in like manner, and continued as long as desired. This machine, as well as the mode of operating by it, will be found highly convenient and useful.