402

DIGESTER.

sometimes grooved, or milled, or otherwise ornamented, and occasionally lettered, inwhich case it is made in three separate and moveable pieces, confined by a ring, intowhich they are most accurately fitted, and so adjusted that the metal may be forced intothe letters by its lateral* spread, at the same lime that the coin receives the blow of the

screw-press.

Coins are generally completed by one blow of the coining-press. These presses areworked in the Royal Mint by machinery, so contrived that they shall strike, upon anaverage, sixty blows in a minute; the blank piece, previously properly prepared and an-nealed, being placed between the dies by part of the same mechanism.

The number of pieces which may be struck by a single die of good steel, properlyhardened and duly tempered, not unfrequently amounts at the Mint to between three andfour hundred thousand, but' the average consumption of dies is of course much greater,owing to the variable qualities of steel, and to the casualties to which the dies areliable: thus, the upper and lower die are often violently struck together, owing to anerror in the layer-on, or in that part of the machinery which ought to put the blank intoits place, but which now and then fails so to do. This accident very commonly arisesfrom the boy who superintends the press neglecting lo feed the hopper of the layer-onwith blank pieces. If a die is too hard, it is apt to break or split, and is especially sub-ject to fissures, which run from letter to letter upon the edge. If too soft, il swells, andthe collar will not rise and fall upon it, or it sinks in the centre, and the work becomesdistorted and faulty. He, therefore, who supplies the dies for an extensive coinage hasmany accidents and difficulties to encounter. There are eight presses at the Mint, fre-quently at work for ten hours each day, and the destruction of eight pair of dies per day(one pair for each press) may be considered a fair average result, though they much morefrequently fall short of, than exceed this proportion, it must be remembered that eachpress produces 3600 pieces per hour, but, making allowance for occasional stoppages, wemay reckon the daily produce of each press at 30,000 pieces; the eight presses, there-fore, will furnish a diurnal average of 240,000 pieces.

DIGESTER is the name of a strong kettle or pot of small dimensions, made verystrong, and mounted with a safety valve in its top. Papin, the contriver of this appa-ratus, used it for subjecting bones, cartilages, &c. to the solvent action of high-pressuresteam, or highly heated water, whereby he proposed to facilitate their digestion,the stomach. This contrivance is the origin of the French cookery pans, called• autoclaves, because the lid is self-keyed, or becomes steam-tight by turning it roundunder clamps or ears at the sides, having been previously ground with emery to fit theedge of the pot exactly. In some autoclaves the lid is merely laid on with a fillet ollinen as a lute, and then secured in its place by means of a screw bearing down upon itscentre from an arched bar above. The safety valve is loaded either by a weight placevertically upon it, or by a lever of the second kind pressing near its fulcfum, anacted upon by a weight which may be made to bear upon any point of its graduate

itJIIi.

Chevreul has made a useful application of the digester to vegetable analysis- *V.instrument consists of a strong copper cylinder, into which enters a tight cylinder of si ~ver, having its edge turned over at right angles to the axis of the cylinder, so as to f° rthe rim of the digester. A segment of a copper sphere, also lined with silver, stops 1aperture of the silver cylinder, being applied closely to its rim. It has a conical vapressed with a spiral spring, of any desired force, estimated by a steelyard. This spri ^is enclosed within a brass box perforated with four holes; which may be screwed wtapped orifice in the top of the digester. A tube screwed into another hole servesconduct away the condensable vapors at pleasure into a Woulfe’s apparatus. r .

DISTILLATION (Eng. and Fr.; Branntweinbrennerei, Germ.) means, in the com ^cial language of this country, the manufacture of intoxicating spirits ; undercomprehended the four processes, of mashing the vegetable materials, cooling the jpeexciting the vinous fermentation, and separating by a peculiar vessel, called a stt • > ^alcohol combined with more or less water. This art of evoking the fiery d em . en tdrunkenness from his attempered state in wine and• beer, was unknown to the 8 ^

Greeks and Romans. It seems to have been invented by the barbarians of the »o ( j, cEurope , as a solace lo their cold arid humid clime; and was first made k’.'‘''V,' vrI] {ir.dsouthern nations in the' writings of Arnoldus de Villa Nova, and his pulnb ,j on ofLully of Majorca , who declares this admirable essence of wine to be ari eman ^ ; n u-the Divinity, an element newly revealed to man, but hid from antiquity, becaus . gg ofman race were then too young to need this'beverage, destined to revive the e p |j wasmodern decrepitude. He further imagined that the' discovery of this aqua »'*'*> wo rld.called, indicated the approaching consummation of all things— the end of 1“. (ed itsHowever much he erred as to the value of this remarkable essence, he truly P re a i; z edvast influence upon humanity, since to both civilized and savage nations it hnsgreater, ills than were threatened in the fabled box of Pandora.