painfully experienced by the purchaser of modern jewellery. The following table will, therefore, prove highly useful to the reader in determining the value of articles in gold, provided he ascertain the fineness of the metal, either by examination or written war

Sterling value of Gold of different degrees of

increase of volume. The property (already
pointed out) that steel possesses of becoming
hard after being heated to redness, and
suddenly chilled, does not belong to pure iron,
such as may be obtained by electrolysis.
Unlike pure iron, too, steel presents a granular
instead of a fibrous structure when broken; ranty:-
the best samples closely resembling silver in
this respect. The chemical difference between
hard and soft steel appears to consist in the
much more intimate combination of the
carbon with the iron in the hard variety than
in the soft. In this latter kind the carbon
seems to be only mechanically mixed, for if it
be immersed in hydrochloric acid the iron is
dissolved, and leaves the carbon behind.
Steel is the most tenacious of all the metals,
being greater than that of either cast or
malleable iron.

What is termed case-hardening (which see) is a process by which small articles of iron, such as keys, gun-locks, &c., are superficially converted into steel. It is performed by heating the articles in contact with iron filings or powdered charcoal. Another method is to make the iron substance red hot, and then to sprinkle powdered potassic ferrocyanide all over it.

STEREOCHROMY. This is a branch of the pictorial art confined to the embellishment of walls and monuments. In the operations by which it is accomplished it will be seen that the soluble silicates (water glass) play an important part.

The foundation for the future picture or coloured design must be of some durable stone or imperishable cement. Over this is first placed a layer of lime mortar, to which is applied when it is dry and has become sufficiently hard, a solution of water glass, by which all the interstices of the mortar are filled up. Another coating of mortar made of sharp sand and a lye of chalk is next laid on, and this, after it has been carefully smoothed, properly levelled on the surface, and become quite dry, is washed over and thoroughly impregnated with water-glass solution. When this last layer has become dry it is ready to receive the painting, which must be executed in water colours. After laying on these colours may be permanently fixed by covering them with water glass. The following are the colours used:-Zinc white, chrome green, chrome oxide, cobalt green, chrome red, zinc yellow, oxide of iron, sulphide of cadmium, ultramarine, ochre, &c. Vermillion is inadmissible, since, in fixing, it turns from red to brown. Cobalt ultramarine, on the contrary, increases greatly in brilliancy upon the application of the fixing solution. Stereochromatic paintings are found to be very durable, and impervious to damp, smoke, or variations of temperature.

STEREOTYPE METAL. See TYPE METAL. STER LING. The truth of the old proverb, that "all is not gold which glitters," is often

Carats.

Fine.

24 carats

23

22

'Fineness.'

21

20

3 10 91

19

18

(lowest Hall-mark). 3 3 8

STEREO-METAL. A remarkable alloy re cently invented by Baron de Rosthorn, of Vienna, and used in place of ordinary gunmetal. It consists of copper and spelter, with small proportions of iron and tin, and to these latter its peculiar hardness, tensile strength, and elasticity, are attributed.

STETH'OSCOPE. An instrument employed in auscultation. It consists of a tube (usually made of wood, sometimes of gutta percha) widening considerably at one end, and but slightly at the other. The wide end is applied to the chest or other part of the patient, the physician putting his ear at the other end; and from the sounds emitted by the heart, lungs, &c., the state of these parts is ascertained.

STEW'ING. A method of cooking food intermediate to frying and boiling, performed by simmering it in a saucepan or stewpan, with merely sufficient water to prevent burning, and to effect the object in view; the whole being served up to form the dish.' It is undoubtedly the most simple and economical, and, when skilfully conducted, one of those best calculated to develop the flavour and nutritious qualities of animal food. The following is one of the most popular stews:

Stew, Irish. Prep. (Soyer.) Take about 2 lbs. of scrag or neck of mutton; divide it

into ten or twelve pieces, and lay them in the to a very extended heated service; whilst pan; add 8 large potatoes and 4 onions cut it effects the evaporation of the alcohol into slices, season with 14 teaspoonful of pep-from the wash by passing a current of steam per, and 3 do. of salt; cover all with water, through it. put it into a slow oven, or on a stove, for two hours, then stir it all up well, and serve it up in deep dishes. If a little more water is added at the commencement, you can take out, when half done, a nice cup of broth.

The wash is pumped from the wash charger' into the worm-tub, which passes from top to bottom of the rectifier. In circulating through this tube it experiences a slight elevation of temperature. Arrived at the last convolution of the tube in the rectifier, the wash passes by the tube M in at the top of the analyser. It falls, and collects on the top shelf till this overflows, whence it falls on the second shelf, and so on to the bottom. All the time this operation is going through fine holes in the shelves, and through valves opening upwards. As the wash gradually descends in the analyser it becomes rapidly weaker in alcohol, partly from condensation of steam which is passed into it, and partly from loss of alcohol, either evaporated or expelled by the steam, till when it arrives at the bottom it has parted with the last traces of spirits.

STILL. A vessel or apparatus employed for the distillation of liquids on the large scale. The forms of stills, and the materials of which they are made, vary according to the purposes for which they are intended, some being exceedingly simple, whilst others are equally elaborate and complicated. The engr. repre-on steam is passed up from the steam boiler sents the most common and useful apparatus of this kind, and the one almost exclusively employed in the laboratory. It is used as follows:-After the fluid and other matters (if any) are put into the still, the head is placed on and connected with the worm-tub or refrigerator, and the joints are all securely luted. For ordinary liquids, a stiff paste made with linseed meal and water, to which a little chalk may be added, answers well for this purpose. At the same time the vapour, as it rises For corrosive liquids, nothing is better than through each shelf of the analyser, becomes elastic bands or rings interposed between the constantly richer in alcohol, and contains less joints, which are then brought home,' as it is and less water because of its condensation; it called, with screws or clamps. Heat is next then passes from the top of the analyser in at applied, and the worm-tub is supplied with the bottom of the lower compartment of the cold water in sufficient quantity to preserve its rectifier. Here it ascends in a similar way, contents at a proper temperature; the applica. bubbling through the descending wash, until tion of the heat being so regulated that the it arrives at F, above which it merely circuliquid may drop from the end of the refrige-lates round the earlier windings of the wash rator quite cold and unaccompanied with vapour. For highly volatile liquids a closed receiver should be provided.

pipe; the low temperature of which condenses the spirits; which, collecting on the shelf at F. flows off by the tube into the finished spirit condenser.

To still further effect a saving of heat, the water for supplying the boiler is made to pass through a long coil of pipe, immersed in boiling spent wash, by which means its temperature is raised before it enters the boiler.

Another variety of distillatory apparatus is that of Siemens' (see page 1567), much employed in the distillation of brandy.

It consists of two mash stills set in a boiler, and capable of being alternately used by means of the three cocks (a, b, and c). L is the boiler; P one of the mash retorts; K is the low wine

a. Body of still, which may be either placed in a steam receiver; R the fore warmer, a reservoir in jacket or in a brick furnace.

b. Still head or capital.

c. Worm-tub.

d. Pewter-worm or refrigerator.

e. Cold-water pipe.

f. Waste-pipe.

9. Receiver.

Of the various forms of distillatory apparatus that patented by Coffey in 1832 is the one almost universally employed in this country. It yields the strongest spirits obtainable on a large scale. Coffee's still (of which a drawing is given on the next page) effects a great economy in the expenditure of heat, by causing the liquid to be exposed

which the condensed water intended as feed water of the boiler is collected; c is the dephlegmator; B a reservoir for the vapours condensed in c.

From the dephlegmator the vapour passes to a condenser, not shown in the engraving.

The mash warmer consists of a cylindrical portion (ii), the lower part of which has an indentation (c). In the cylinder is placed a narrower portion (o o) of the real mash, containing a vessel, fitted with the heading tube (fn). The upper part of the fore warmer is fitted to the lower part by means of the flange (hh); r is a stirring apparatus, which is fre

Siemens' Distillatory Apparatus. quently set in operation during the process of distillation. The vapours from the second still are carried into the depression (c) under the fore warmer, which, in order that the vapours may come into contact with the phlegma, is covered with a sieve.

The vapours surround the under part of the mash reservoir, and enter into the tube (f), through which they pass to the lower cylinder of the dephlegmator. The condensed water of the dephlegmator is conducted into the reservoir (A). The upper and under part of the fore warmer are made of cast iron, but the interior bottom and heating surfaces are made of copper. This kind of fore warmer has the advantage of uniformly distributing the heat, while it can be easily cleansed.

The dephlegmator (c) is so contrived that the rectified vapour can be conveyed to the condenser by two separate pipes placed in an opposite direction to each other, which are joined again in close proximity to the con

denser.

The remainder of the details will be seen by studying the engraving.

The engraving on page 1568 gives a representation of it.

It consists of two stills (A and A'); the first rectifier (B); the second rectificator (c); the wine warmer and dephlegmator (D); the con denser (F); the regulator (E); a contrivance for regulating the flow of the fluid wine from the cistern (G).

The still A', which, as well as the still A, is filled with wine, acts as a steam boiler. The low wine vapours evolved come, when they have arrived in the rectifiers, in contact with an uninterrupted stream of wine, whereby dephlegmation is effected; the vapour, thus enriched in alcohol, becomes stronger in the vessel (D), and thus arrives at the cooling apparatus (F). In order that a real rectifica tion should take place in the rectificators the stream of wine should be heated to a certain temperature, which is imparted to it by the heating of the condensed water. The steam from the still a' is carried by means of the pipe (z) to the bottom of the still A.

Another distilling apparatus is that known Both stills are heated by the fire of the as Derosne's, which is an improvement upon same furnace. By means of the tube B' the one invented by Cellier-Blumenthal. This liquid contained in the still a can be run into the apparatus is only designed for the distillation still A'. The first rectificator (B) containing a