of the solid silver. The art of enamelling on precious metals in the high artistic acceptation of the term has been virtually lost to jewellers for the last century and more. In India it still lingers among a few families of the native jewellers; in Europe it has almost disappeared. The Messrs. Elkington, of England, are now making an effort to revive this lost art, and exhibited numerous objects illustrative of their progress and success. The pattern is first cut out of the metal; on the hollow spaces thus formed the enamel is placed, and fused under a violent heat. When cool, the rough surface is polished on a stone lathe. A dessert service in this style was very beautiful, being in the Pompeian style, the enamel employed being turquoise blue, red, and black. Its value was ten thousand dollars. A magnificent electro-plated dinner service, some of the pieces of which were executed in the enamel style, -made by this firm for the Duke de Brabant, though not of silver, was so elaborate in its design, and so finished in its execution, that its actual cost was estimated at thirty thousand pounds- one hundred and fifty thousand dollars. Messrs. Hunt & Roskill, of London, displayed an elaborate silver candelabra, made for the Marquis of Breadalbane, to display his celebrated collection of the Poniatowski gems. It was so constructed as to hold lamps, round the globes of which, in silver-gilt bands, the gems were set, so that the light shines through them, displaying the colors of each, and the minute design which enriches them. The body of the candelabra, from which these branches spring, likewise contains a magnificent belt of gems, and into this, also, a light is introduced to set them off to the best advantage. Between the plaques of repoussé work here, the body of the vase is filled up with iron, damascened all over with the most exquisite and minute arabesques in gold.

Emanuel, of London, showed a gold cup, representing the fable of Perseus and Andromeda, in which advantage was taken of the peculiar form of a very large topaz to cut it into the shape of a small nautilus shell, and this stone forms the cup proper. All the rest of the work, the stand, stem, etc., was of gold enamelled. The dragon, a most Raffaelesque monster, is made to subserve the purpose of a handle, and waits, open-mouthed, for the descent of Pegasus and his rider. This cup sold during the Exhibition for $10,000. In the same case with the above was exhibited a very fine specimen of gold work in the shape of a toilet mirror, which was made for the late Sultan of Turkey, as a present for one of the ladies of the harem. Its cost, it being profusely adorned with precious stones, was £10,000 ($50,000). With this another present was to have been made to the same favored lady, of a stereoscope in ivory, enriched with rubies and emeralds; and this costly work was also shown, though, as the laws of optics could not be moulded to suit the requirements of jewellers' tastes and fashions, the stereoscope in its dress of jewels remained quite as angular and ugly in regard to shape as one of common mahogany.

In the speciality of precious stones, the display of the Exhibition was, probably, the finest and most extensive the world has ever seen. It embraced the well-known Koh-i-noor, with a companion diamond, weighing seventy-six and one-half carats, belonging to the queen; the celebrated "Star of the South" diamond, larger than the Koh-inoor, and owned in Amsterdam; and three of the finest rubies known,

which, found in the treasury of Lahore, India, were confiscated and given to the queen. They are engraved with dates of the Mohammedan era from 1070 to 1168. Other curiosities were an emerald, almost without a flaw, weighing one hundred and fifty-six carats; another emerald, imperfect, weighing three hundred and seventyseven carats, and claimed to be the largest in the world; a ruby, weighing one hundred and one carats, and a small profile likeness of the queen, not much larger than a postage-stamp, which was composed of nearly twelve hundred minute but distinct diamonds. Emanuel, the celebrated London jeweller, showed many specimens of an old fashion of setting precious stones in ivory, that is, "ivory-jewelry;" and a more attractive setting for some kinds of gems, viz., that styled the "pink coral" jewelry. This material, however, has nothing to do with coral, the pink base in which the jewels are set being cut out of a delicately-tinted shell found in the West Indies, which much resembles rose-colored mother-of-pearl. With the aid of this shell and the ivory some remarkably beautiful combinations are produced, especially when the jewels are carefully chosen to suit the settings.

Other novelties in jewelry were the so-called "rock-crystal brooches," engraved like intaglios, and painted from the back; their curiosity consisting almost entirely in the excellence of the painting, which requires great skill, inasmuch as the first touch of the brush must also necessarily be the last; the "granite jewelry," manufactured in Aberdeen, Scotland, some specimens of which were very fine, the grain of the stone revealing depth and richness of hues; and a cup, taken from the Emperor of China's palace, made of a human skull, inlaid with precious stones and supported upon a massive gold pedestal.

In the French department a most curious exhibit was made of artificial pearls and gems. One exhibitor showed ten strings of pearls,

one, real, valued at twenty thousand dollars, and another, false, worth two hundred dollars, and defied connoisseurs to distinguish, by sight alone, between the two. The false gems, for which the French are so justly celebrated, were exhibited in every stage of manufacture, from the mass of paste composition in the crucible to the cut and set stones. Here, again, the eye is completely at fault, the taste of the manufacturer leading him to discard all extravagances, the more completely to deceive. The price of these fictitious gems was, however, very high.

Aluminum was shown in a great variety of useful and ornamental forms. We would specify soldiers' helmets and sextants, both wonderfully light; also door-keys of aluminum alloyed with a small percentage of nickel. A fine display was made of fancy articles composed of ten parts alloyed with five of copper, the whole an alloy of great hardness, of the exact color of gold, and almost as free from liability to tarnish as the precious metal itself. At present the price of aluminum has fallen to about seventy cents per ounce, and for jeweller's work one ounce of aluminum will go as far as five or six of silver. M. Garepou, of Paris, now furnishes aluminum wire at from sixty to one hundred per cent. cheaper than silver wire of the same size. He exhibited in the Exhibition articles of lace-work, epaulets, textile fabrics, head-dresses, etc., with mountings and ornaments constructed entirely of aluminum.

In this department was exhibited an ingot of platinum, weighing

over two tons.

PAINE'S SPRAY SUPERHEATED STEAM-ENGINE.

This engine, for which steam is generated on a very ingenious principle, differs from an ordinary steam-engine in the following essentials: For the latter, as everybody knows, a boiler is used containing a considerable quantity of water, to which the heat of the furnace is most directly applied, and from which the steam is generated. Such a boiler is a magazine of force, because it contains a far greater amount of steam and heated water than is required to supply the engine at each stroke. Herein consists the danger from explosions in common boilers. A hot-air engine has no magazine of force like a steam-boiler. Its heater is supplied with the exact amount of air requisite for each stroke, hence its immunity from explosion. This new engine embraces a similar principle. It has a peculiarly constructed heater, into which the exact quantity of water for each stroke is fed in the form of spray, then it flashes into steam, and passes over an extended heated surface to the working cylinder.

A single acting engine, working in New York, has the following dimensions: Its steam cylinder is seven inches in diameter; the stroke of piston, seven inches. It is situated upon a small tank thirty by thirty-four inches, which forms the bedplate and the heater of the feed-water. The feed-pump has a stroke of one-fourth of an inch, and the water is fed through a quarter-inch pipe. The steam-heater, outwardly, resembles a vertical cylindrical stove. It is thirteen inches in diameter, and thirty inches in height. There are nineteen double tubes inside, and the steam passes between these, and is heated on two sides. The circular grate, containing the fire, is capable of being adjusted by a lever, and set at any required distance from the bottom of the heater. The steam exhausts into the tank upon which the engine stands; the feed-water, nearly at the boiling temperature, is conveyed into the heater in a fine shower through a small conical chamber on the top of the heater. A small quantity of superheated steam is contained in the heater, and the feed-water, in the form of spray, is instantly converted by it into saturated steam. The pipe for supplying the cylinder with steam is situated nearly at the bottom of the heater; hence the saturated steam formed from the feed-water at the top of the heater has to pass in a current between the double tubes on its way to the cylinder, and it thus flows over a very extended heating surface and becomes superheated. A constant current of steam is maintained in this manner over the heated surfaces of the tubes. By such a heater and such arrangements of the parts of the engine, nearly all the heat is economized, and a perfectly safe steam-engine is secured. If the feed-pump were to cease working or the supply of water to become exhausted, the heater would become like an empty oven after a few strokes, and the engine would stop of itself. For pumping water, printing-presses, sawing wood, and various operations requiring a small motor from one to ten horse-power, this engine appears to be well adapted, as it is compact, safe, and easily controlled. Scientific American.

THE PNEUMATIC DISPATCH.

It

The principle of forcing packages, etc., through a tube or conduit by means of atmospheric pressure, is about to be applied practically and upon a large scale in London (see Annual of Scientific Discovery, 1861 and 1862) for conveying or pumping the mail from Easton Square (a great railroad depot) to a post-oflice station some miles distant. The tubes to be used for this purpose, and which are to be laid underground, are about three feet in diameter, and of the form of a horseshoe. At the bottom of the two sides of the tube is a slight projection, which does duty as a line of rails, on which the carriages roll along. The latter have a board behind and in front, which fits into the tube, but by no means in an air-tight manner. is said that this is not in the least necessary, and that it was a great mistake on the part of former schemers in atmospheric railways to encumber their tubes too much with wadding and bolstering, which led to a greater loss by friction than was gained in power. To allow for the inequalities of the tubes, there is more than half an inch space between the outer shell of the boxes and the inside of the iron pipe, and it is found that even with this margin they travel at the rate of forty miles an hour. The tube is exhausted by an apparatus called a "centrifugal disc," concisting of a hollow wheel, twenty-one feet in diameter and but a few inches in thickness, which in its centre literally sucks up the air and discharges it at the outer edge. This is effected by a division of the disc into a number of small chambers, which act like so many fans in gathering and emitting the air. It is a very simple and beautiful contrivance, which is found to work admirably, much more efficient and very considerably cheaper in its action than an air-pump. A small steam-engine puts this disc in movement to the time of from two hundred to three hundred revolutions a minute. It requires but a short time to exhaust the air of a tube several miles long to a sufficient extent to propel a whole train of letters and parcels. Judging from the success of the experiments already made, the scheme bids fair to be realized before long on a grand scale, and produce a revolution in the dispatch of letters as great at least as that of the introduction of the penny-postage. There seems no reason, indeed, why our letters should not be carried to us in pipes underground as well as our gas and our water.

THE MONT CENIS TUNNEL.

As the work on this great tunnel is now advancing, day by day, with such a regularity and success as to render it one of the most wonderful of engineering feats in the world's record, a brief review of the history and progress of the enterprise will not be found uninteresting.

The tunnel, it may be premised, is in the course of construction under the auspices of the Sardinian government, and is intended to subserve the purpose of railway communication between Piedmont and Savoy. It passes beneath what is known as the Frejus Ridge, in the vicinity of Mont Cenis; has an average depth of about a mile below the surface, and a length of about eight miles. As shafts a mile

in depth were out of the question, it was determined in the outset that the tunnel should be worked from the extremities alone; that is to say, that four miles should be worked from one end and four from the other. These conditions, however, involved two great difficulties: one, the immense time which it would take to excavate so long a tunnel from both faces, and the other the apparent impossibility of ventilating it during the progress of the work. In order to obviate these difliculties, various plans were proposed, but, after considerable consultation on the part of the engineers intrusted with the matter, the following arrangement was adopted. Air in the first instance is forced into reservoirs, from whence it flows uniformly through a tube into the interior of the tunnel or heading. This air is first used to work the tools for drilling holes in the face of the rock, and then allowed to escape in the tunnel-shaft, which last secures a perfectly good ventilation.

As this hydro-pneumatic machinery is the principal agent used in carrying out the work, it is necessary, in the first instance, to get a clear idea of the manner in which it acts. Some 30 or 40 yards above the level of the plain there is a reservoir of water, filled by a canal that is fed by a supply from a mountain torrent at some considerable distance away. From this reservoir there are ten iron cylinders laid on beds of masonry against the steep slope of the mountain, each of which can be made to receive the water from the reservoir by opening valves up above, in which case the water rushes down into iron reservoirs for storing the air, one of these last being connected with each tube that is laid against the side of the mountain.

The way in which the air is forced into the iron reservoirs is as follows: Each tube that comes down the side of the mountain, and which is about two feet in diameter, is continued on some ten or twelve feet below the floor of the atelier, or building in which the reservoirs are placed, after which it is bent and rises up perpendicu larly, or rather the main tube communicates underneath with a hollow vertical column from 12 to 15 feet high, in the top of which is a valve opening downwards; there is also another valve to separate the sloping part of the tube from the horizontal portion. The whole of the tube, including the sloping part between the water reservoir on the side of the mountain and the flow of the atelier, the horizontal part beneath the floor, and the vertical part which rises in the atelier some 12 or 16 feet, form altogether a siphon, in which not only the weight of the water acts, but also the momentum of the water descending all the way from the lofty mountain ridge whence it originally proceeds. We may suppose the whole of this siphon filled by water, to begin with. The first operation then, in working, is to close the valve at the foot of the sloping part, and afterwards to discharge the water in the horizontal and vertical portions of the tube; this being done, the valve at the top of the vertical column falls down and admits the air. The valve at the foot of the sloping tube is then reopened, and the one at the top of the vertical column closed; the water then rushes in and compresses the air in the shorter end of the siphon to six atmospheres. This water afterwards is discharged as before, and fresh air admitted; but it should be understood that when the air is compressed in the upper portion of the vertical cylinder it