Among the many very curious experiments made with the blow-pipe by Dr. Clarke, the following may be adduced as examples. Several oriental rubies being placed on charcoal, their fusion was so rapid that he feared they would volatilize. They ran together into a bead, and remained in such a liquid state before the gas, that the current of it penetrated like a stream of air upon oil, when urged by a pair of bellows. The bead, when examined, was white and opaque; all colour having disappeared. Being again exposed to the ignited gas, and taken from the charcoal by iron forceps, its surface was covered by a thin flaky metallic substance, which came off on the fingers, glittering like scales of carburet of manganese. On being fused a third time, it assumed a variety of shapes, like sapphire during fusion. The reduction of the oxide of tin afforded an easy and very beautiful experiment. Wood-tin, exposed to the ignited gas, communicated a beautiful blue colour, like that of violets, to the flame. In employing a pair of iron forceps, as a support, the iron became covered with an oxide of tin of incomparable whiteness. The fusion was rapid; and when the wood-tin was placed on charcoal, the metal was revived in a pure and malleable state. In effecting the fusion and combustion of platinum, the largest drops which fell from the melting of platinum wire, when exposed to the utmost heat, weighed ten grains; but drops of metal weighing fourteen grains were obtained, when the current of gas was diminished so as not to let the metal run off too quickly from the wire. By placing several globules on a piece of charcoal, and suffering the whole force of the gas to act upon them, the metal was made to boil, and they all ran together into one mass.

THE SAFETY LAMP.

THE invention of the wire-gauze-safe-lamp, for preventing explosions from fire damp, and for giving light in explosive atmospheres, is due to Sir Humphrey Davy, who remarks that the dreadful accidents of explosions are occasioned by the firing of light carburetted inflammable gas, which is disengaged during the working of the coals, and from fissures in the strata ; and which, when it has accumulated so as to form more than 1-13th part of the volume of the atmospherical air,becomes explosive by a lighted candle,

or by any kind of flame. The apertures in the gauze should not be more than 1-20th of an inch square. As the fire damp is not inflamed by ignited wire, thickness of the wire is not of importance, but wire from 1-40th to 1-60th of an inch in diameter is the most convenient. If the wire of 1-40th is found to wear out too soon in practice, the thickness may be increased to any extent; but the thicker the wire, the more the light will be intercepted, for the size of the apertures must never be more than 1-20th of an inch square. In the working models which he has sent to the mines, there are 748 apertures in the square inch.

When the wire-gauze-safe-lamp is lighted and introduced into an atmosphere gradually mixed with fire-damp, the first effect of the fire-damp is to increase the length and size of the flame. When the inflammable gas forms as much as 1-12th of the volume of the air, the cylinder becomes filled with a feeble blue flame, but the flame of the wick appears burning brightly within the blue flame, and the light of the wick continues till the fire-damp increases to 1-6th or 15th, when it is lost in the flame of the fire-damp, which in this case fills the cylinder with a pretty strong light. As long as any explosive mixture of gas exists in contact with the lamp, so long it will give light, and when it is extinguished, which happens when the foul air constitutes as much as 1-3d of the volume of the atmosphere, the air is no longer proper for respiration, In cases in which the firedamp is mixed only in its smallest explosive proportion with air, the use of the wire-gauze-safe-lamp, which rapidly consumes the inflammable gas, will soon reduce the quantity below the explosive point; and it can scarcely even happen, that a lamp will be exposed to an explosive mixture containing the largest proportion of fire-damp: but even in this case the instrument is absolutely safe; and should the wires become red hot, they have no power of communicating explosion. Should it ever be necessary for the miner to work for a great length of time in an explosive atmosphere, by the wire-gauze-safe-lamp, it may be proper to cool the lamp occasionally by throwing water upon the top, or a little cistern for holding water may be attached to the top, the evaporation of which will prevent the heat from becoming excessive.

THE GAS-LIGHT APPARATUS.

THIS apparatus consists of an iron retort, about 3 feet long, and two feet in diameter, open at one of its extremities, to which is screwed, by means of a flaunch, a door piece to this the door is applied, and is shut close by a screw placed in the centre. The coals to produce the gas are shut up in the retort, and the whole heated to redness by a fire applied underneath, the retort being placed in a sort of oven or furnace, so that the heat surrounds every part, except that at which the coals are introduced. Around the space of this oven a flue leads from it to the chimney, the aperture of which is regulated by a small damper. A plate of cast iron preserves the retort from being injured by the intensity of the fire underneath it, and causes it to be heated more uniformly. A cast iron pipe conveys all the volatile products of the coal to a refrigeratory of cast iron, in which the tar, &c. extracted from the coal are deposited, and whence they can be drawn off by means of a copper pipe. The gas is conveyed from the refrigeratory to the top of a cylindrical vessel or receiver, which is in that part air tight: consequently the gas displaces the water in this receiver, to a level with the small holes made round its inferior edges, where it is suffered to escape, and rises in bubbles, through the water of the well, into the receptacle or gasometer.

This gasometer is made of wrought iron, and is capable of rising, or of sinking down nearly to a level with the top of the well which contains the water, when it will consequently be nearly filled with that fluid; but it rises gradually as the elastic gas enters it from the pipe, and displaces the water. Weights are suspended to balance and keep it steady it is strengthened withinside by two sets of iron stays; its seams are luted to make them air tight; and it is well painted inside and outside to preserve it from rust.

The use of the gasometer is to equalize the emission of the gas, which issues from the retort more quickly at some times than at others. When this happens, the vessel rises up to receive it; and when the stream from the retort diminishes, the weight of the gasometer expels its contents, the balance weight not being quite so heavy as the gasome

ter, in order that a suitable pressure may be exerted to force the gas out at the burners with a proper jet.

The gas, after it leaves the deposit vessel, and before it reaches the gasometer, is passed through a vessel of limewater, to deprive it of every bituminous and sulphureous smell. From the gasometer it enters a tube by small holes made at its top, and, passing on through other tubes, is conveyed by pipes to the burners, or lamps, where it is to be consumed. These burners are formed in various ways, either by a tube ending with a simple orifice, at which the gas issues in a stream, and, if once lighted, continues to burn with a steady and regular light as long as any gas is supplied. At other times a number of very minute holes are made in the end of a pipe, which form as many jets de feu, and have a very brilliant appearance. If the gasometer of a gas-light aparatus has a diameter of five feet by seven feet high, it will contain a sufficient quantity of gas, at four cubic feet per light, per hour, to give forty hours light to a brilliant Argand lamp, or five hours to eight lamps, equal in intensity to one hundred and sixty common street oil lamps. Such a gasometer will be filled by the distillation in the retort of about half a bushel, or a quarter of a hundred weight, of coals. The remains which are found in the retort, after the process is finished, consist of most excellent coke, which in value, for culinary fires, or manufactories, returns a considerable portion of the whole expences.

The experiments made by Mr. Brande, in a small gas apparatus erected in the laboratory of the Royal Institution, lead to the conclusion, that a chaldron of good Wallsend Newcastle coals would afford from 17,000 to 20,000 cubic feet of gas; but the process of distillation, as it has been carried on in the large establishments for lighting the metropolis, has seldom afforded a larger average produce than 12,000 cubic feet. There can, however, be little doubt that, by improvements in the construction and management of the retorts, the highest of the above averages may be obtained. In the month of April, 1816, at the three stations belonging to the chartered Gas-light Company, situated in Peter-street, Westminster, in Worship-street, and in NortonFulgate, twenty-five chaldrons of coals were daily carbonized, actually yielding 300,000 cubical feet of gas, equal to

the supply of 75,000 Argand's lamps, each lamp giving the light of six wax-candles. If the full proportion of gas had been obtained, namely, 20,000 cubic feet from each chaldron of coals, the produce would then have been 500,000 cubic feet, equal to the supply of 125,000 lamps of the same size; and the light then afforded would have equalled that of 750,000 wax-candles, instead of 450,000, which was the real produce. Including that of the City Gas-works, in Dorset street, Blackfriars Bridge, the total daily consumption of coals in London, for the purpose of illumination, then amounted to 28 chaldrons, and the number of lights supplied to 76,500; but this amount has been since greatly augmented, and this invaluable discovery, which now bestows an additional lustre on our theatres, &c. &c. is rapidly communicating its,benefits to every part of the United Kingdom.

LONDON WATER-WORKS.

AMONG works of great magnitude, and displaying a vast ingenuity in their contrivance, may be cited those of the various companies for supplying the metropolis with water, the modes of forcing which into the main pipes, at the heads of the respective establishments, and thence conveying it, by subordinate pipes, through the different streets, so as to afford an ample supply to the inhabitants, as well as to provide against fires, may be reckoned among the most useful of the wonders of art.

The

The NEW RIVER WORKS at Islington claim the earliest notice, as having supplied the capital with pure water for nearly two centuries, at an original cost to Sir Hugh Middleton of £500,000. The reservoir is eighty-five feet above the level of the Thames; but, to give it the necessary force, it is raised thirty-five feet above that level, whence it rises into the second and third stories of most houses. quantity it discharges every twenty-four hours is 214,000 hogsheads of sixty-three gallors each. There are besides, the LONDON-BRIDGE WATER-WORKS, in which a forcing engine serves the purpose of a high level, but the water is not strained nor purified; the YORK-BUILDINGS WORKS; the EAST LONDON WORKS; the SOUTH LONDON; the WEST MIDDLESEX, at Hammersmith and Kensington, on a grand scale, with contrivances for purifying the water; and the