The operations of chopping, powdering, grinding, etc, are so frequently required in cooking, and the other branches of domestic economy, as to render any description of their utility wholly unnecessary; and we may therefore confine ourselves to describing the best means of accomplishing the object desired. Powdering is usually performed by the aid of the pestle and mortar. Most of the works on Cookery recommend the use of a marble mortar; this material is about one of the worst that could be selected for the purpose. In the first place, it is expensive; secondly, it is rapidly corroded, even by the weak acids used for food; thirdly, it is readily stained by oily substances; fourthly, it is absorptive of strong flavors, imparting them readily to the next substance pounded; and lastly, it is brittle, and even if not broken, is not calculated to withstand much wear. By far the best material for the purpose is the Wedge-wood ware; mortars made of it are cheaper, cleaner in use, and stronger than those of marble, and are not corroded by acids or alkalies - their pre-eminence is so great, that they are invariably used by druggists.

The act of powdering requires great tact and practice to perform it neatly and rapidly. After the object has been broken into small pieces by blows from the pestle, a grinding action is required; this should at first be given by striking the fragments, not in the centre of the mortar, but towards the side furthest from the operator; the pestle, by this means, grinds over them in its descent to the centre, and much more rapidly accomplishes their division than if mere blows are given. After the object has been divided to a certain extent, blows are entirely useless, and a grinding in circles becomes requisite; if the circle is confined to one part of the mortar, the same portions get rubbed over and over again, the others escaping; this is avoided by constantly and regularly altering the size of the circles. If they are commenced in the centre, they should gradually increase in size until the sides are reached, and then contract again, and so on. By this means the whole of the powder is brought under the action of the pestle, and the operation is much quicker than if performed at random. One great fault usually committed in powdering, is the endeavor to operate on too large a quantity of material at one time. The operation is much more rapidly conducted if small' portions are taken; and if the material, is tough, and contains much fibrous matter, the process may be very much shortened by removing those parts which are sufficiently powdered, by sifting from time to time through a sieve. This may be objectionable, however, from the fine powder escaping into the air; in this case, the following contrivance will be found useful: A cylindrical tea-canister of the requisite size is taken, with a loosely fitting lid (or if tight, the lid may be enlarged by four slits being made partly up the sides ); a bag of lawn is dropped into the canister, the top being turned over the edge; the powder to be sifted is put in a bag, the lid put on, and, by tapping and shaking, the finest portions pass into the canister without any escaping into the air - a point of very considerable importance where the powder is irritating or expensive.

Fig. 9.

All vegetable, and many mineral substances, are much more readily powdered after having been thoroughly dried; so far is this process carried, that many drugs are dried so as to lose fifteen per cent. of their weight before powdering. After drying, substances should not be exposed to the air, but, unless they are of such a nature as to be softened by heat, are better operated on whilst still warm. Flints are more readily powdered by being heated to redness and quenched in cold water; charcoal, for tooth powder, whilst still warm from drying. Gum can only be powdered whilst perfectly dry. Camphor, which is with great difficulty powdered alone, yields readily if a drop or two of spirit is poured on it. Substances which clog together and cake under the pestle, are not uncommon; to these it is sometimes requisite to add sand, which may afterwards be separated - this prevents the clogging; but its use is often impracticable. Lime, if required in very fine powder, for dusting over plants to kill slugs, etc, is readily obtained by slaking it, when fresh burned, with lotting water; when, if too much water is not used, it falls into an exceedingly fine powder.

Sal-ammoniac, and some other saline bodies, are most readily powdered by dissolving them in as small a quantity of boiling water as possible, and stirring the solution rapidly as the water is boiled away, or as the solution cools. Before dismissing the pestle and mortar, we may allude to its use in mixing powders together, although a much more ready mode of doing this is with a sieve. Two or more powders stirred together and passed two or three times through a sieve, are much more intimately mixed, than if rubbed for a long time in a mortar. Metals cannot be divided in the mortar; the most convenient mode of proceeding, if they are fusible under a white heat, is to melt them, and pour them whilst liquid into a pail of water, which should be full to avoid any spluttering, and the hotter the metal, the more filmy the particles. It is scarcely requisite to state, that the metal should be poured in a circle, so as not to collect at one place.

Chopping is usually performed in the kitchen, with a large common knife; but is more speedily done by some of the improved contrivances similar to the following:- The chopping-board should be made of hard wood, with the grain at right angles to the surface of the board, by which it is rendered much more durable, than if they are parallel to it. The chopping-knives should be fixed at right angles to the handles, and may be either of the preceding patterns. If a large quantity of material has to be acted on, we would recommend a board as above, not less than three inches thick, and smooth on both sides, so that either may be used, of the requisite size - say eighteen inches or two feet in diameter. On this should stand a loose bottomless tub, to confine the materials, and. the whole resting on the floor, should be used with a knife, sufficiently long in the handle to be employed by a person standing erect, and it should have a small cross-bar for the hands, as shown in Fig. 12.

Fig. 10.

Fig. 11.

Small chopping-knives are sold, consisting of three blades riveted together; and a very convenient one is made by fastening, at convenient distances, a number of flat circular disks, sharpened at the edges, to a central axis with a handle at each end.

Many substances, such as stale bread, dried herbs, etc, may be very conveniently powdered by rubbing them through a wire sieve, of the requisite degree of fineness. Herbs intended for use in this way, should be dried as rapidly as possible, without being scorched, in small heaps, before the fire; parsley and others done in this way, may be powdered, retaining their bright green color and flavor, both of which are preserved if they are corked tightly in bottles, and kept in a dry, dark cupboard. The use of waxed paper to preserve dried powders in, or for tying them down in jars, or generally as a very good substitute for bladder, will often be found convenient. It is readily made by laying a sheet of smooth stout paper on a warm iron plate, as the top of a kitchen oven; on this place the thin tissue or other paper to be waxed; put a piece of wax on it, and as it melts, rub it over, spreading it evenly. One end of a cork, covered with two thicknesses of linen, answers very well for a rubber. If a hot plate is not at hand, the sheet of paper may be held before the fire, and rubbed over, as it warms, with the cut edge of a cake of white wax; but this requires the co-operation of two persons.

Fig. 12.