fifth, a piece of copper; and sixth, a piece of cloth; and proceed in this way, placing these substances on the top of one another, precisely in the above enumerated order, till the whole are disposed of. You will then have a plate of metal at each end, but at one end will be zinc and the other copper. The pieces of metal may be soldered together, and it is more convenient that they should be; but then care must be taken in placing them, always to lay the same metal undermost. The cloth must not contain so much of the liquid as that any of it will squeeze out by the weight of the plates above. To preserve the pile upright, it may be placed within four rods; or if too high, it may be divided into two or more equal parts, each part being connected both at top and bottom by slips of metal. In this case, however, it is essential that the same order be observed and continued through all the parts, up the first pile, down the second, up the third, and so on. A galvanic pile, constructed in this manner, retains its power for a considerable time, namely, as long as the cloth is moist; and this power is in proportion to the number and size of the plates.

The mode of using this pile is very simple. The shock may be taken, to use our Correspondent's language, by applying the two hands, one to each extremity of the pile; and the shock is felt the instant the second hand grasps the end of the pile. For making chemical experiments, a piece of wire, made of the same metals, is soldered to the outer surface of the plate at each extremity of the pile. Gold or platinum wire answers the same purpose better, because the positive wire of any other metal is speedily oxidated. The two extremities of these wires are then brought nearly into contact, in a glass vessel containing the mixture to be experimented on, or the substance to be decomposed is placed between the two ends of these wires. In taking shocks wires may also be used.

We believe we have now given our Correspondent all the information he required. At the same time, we must add, that at present galvanic troughs are much more used than piles. They are made of stoneware, having a number of partitions right across, between which plates of the above metal, soldered together, may be inserted at pleasure, they being all connected together at the top by slips of metal passing from one to the other, the trough containing at the same time a solution of one of the acids mentioned above. Galvanism, as well as electricity, illustrated by Plates, will hereafter be treated of in their proper place, as they form essential and important branches of the science of chemistry.

PROTOIODIDE OF CARBON. M. SERULLAS has announced in the Annales de Chimie et de Physique, No. 25, p. 311. that he has discovered a protoiodide of carbon, and that it has the following properties:-It is liquid, heavier than sulphuric acid; seen under water it is of an opaque white, which appears to depend on the water: after being agitated in a solution of caustic potass it becomes transparent and of a slight lemon colour; its smell is very penetrating and agreeable; its taste very sweet, very lasting, and accompanied by a sensation of freshness, similar to what is produced by mint. It is soluble in water, to which it communicates in a very marked manner its taste and smell. A solution of chlorine has no action on it, but chlorine in the state of gas rapidly decomposes it. Sulphuric acid has no action on it. When exposed to the air, or placed under water in close vessels, it becomes immediately of a rose colour, which gradually increases in intensity. It does not take fire in contact with a lighted candle. Oxygen saturated with the protoiodide of carbon, either alone or mixed with pure oxygen, does not take fire either by the application of a lighted taper or the passage of the

electrical spark. It is obtained by mixing equal parts of the perchloride of phosphorus with the periodide of carbon, perfectly dry, in a phial with a bent tube, the end of which is plunged in water, kept very cold. The mixture is heated sufficiently to fuse the periodide of carbon, and in a short time vapours of iodine rise; then the protoiodide flows into the tube, of a red colour, whence it passes into the vessel containing water, goes to the bottom, and speedily becomes colourless.

DICTIONARY OF CHEMISTRY, IN compliance with the expressed wish of several of our subscribers, we intend to give in successive Numbers a brief Diction

ary of Chemical Terms. Each Number will probably contain ten till the whole is exhausted.

ACETATES. In chemistry the term salts is usually employed to denote all the compound bodies formed by an acid and an alkali, a metallic oxide or an earth, and in this sense acetates is the name applied to all the salts formed by a combination of acetic acid with alkalies, earths, or metallic oxides.

ACETIC ACID. A peculiar acid obtained from the juices of many plants. This term is also sometimes applied to vinegar, vinegar being in fact a very much diluted and somewhat impure acetic acid, ACETOMETER. An instrument for ascertaining the strength of vinegar.

ACIDS. A large and very important class of bodies. As this word is used by chemists it is much more extensive in its meaning than in common life, and comprehends all substances which have a sour taste, which change vegetable blues to red, and which combine with alkalies, earths, and metallic oxides, forming those compound substances called salts. At present chemists enumerate 87 acids.

ACIDIFIABLE. In chemistry this means a capability of being converted into an acid by an

ACIDIFYING PRINCIPLE. It has

been asserted by chemists, that there was but one substance which possessed the power of converting other substances into acids, and oxygen was supposed to be this substance, and was therefore denominated the acidifying principle. At present, however, acids are known in which no oxygen has been, or can be detected; and the acidifying principle is now given up..

ACONITA. A poisonous vegetable substance, of an alkaline nature, extracted from the aconitum napellus, or wolfsbane.

ADAMANTINE SPAR, A remarkably hard stone, which is found in India and China, and is used for polishing gems.

ADEPTS, among the alchymists, signified those who had discovered the philosopher's stone, but who were not at liberty to reveal the

secret.

ADIPOCERE. A curious kind of fat-like substance, somewhat resembling spermaceti, into which animal matters are converted by an incomplete putrefaction.

LUMINOUS BOTTLES. To the Editor of the Chemist. SIR, I have recently seen in your little publication, and in some of the other numerous weekly ones, methods for quickly producing light, &c.; and in a newspaper, Feb.1824, that" Messrs. Arago and Fresnel have invented a lamp with concentric fires of very brilliant and superior properties," &c; and previous to that, that some foreigners had discovered a method of making a corked bottle luminous by the aid of factitious air.

Now, Sir, I wish to know, if there is any method of making a vessel (say a decanter, for instance) luminous when the external air is excluded, or, in other words, when it is corked. Or can a decanter be made luminous (of course I mean without any sort of fire) when free admission is afforded to the atmospheric air; and how long in either case, and in both cases, will they continue luminous without replenishing, &c. The more luminous

PHOSPHORESCENCE OF ACETATE OF LIME.

DISSOLVE any quantity of acetate of lime in water, and place it in a sand bath, in a wedgewood evaporating-dish, and evaporate it to dryness without disturbing it. When quite dry, let the ball of a thermometer be rested on the bottom of the dish, and when the temperature has attained 250° F. the lime will adhere very firmly to the bulb. If light be now excluded, and the acetate strongly rubbed with a stiff spatula, it will become highly luminous.-Annals of Philosophy.

CURIOUS EXPERIMENT. We mentioned some months ago an experiment exhibited in Professor Leslie's Class-room, in which a hollow brass sphere was balanced on the top of a jet of water, and made to play up and down, in a manner very striking and beautiful. We saw the Professor exhibit subsequently an experiment of the same kind with air, but of a more novel and singular description. Two or three atmospheres of common air were condensed into a close copper vessel, of a size which might be conveniently carried in the hand. A stop-cock, with a very minute aperture, fixed on the top of the vessel, being opened, the condensed air rushes out in a stream. If a wooden ball of the size of a school-boy's marble, or larger, is placed by the hand in this current of air, it is not blown

aside or suffered to fall, as we would expect, but continues to leap up and down some inches above the orifice, generally performing at the same time a vertical revolution round its axis. Though the air and water in the two experiments perform the same office, they act in a very different manner. The water, thrown up by pressure, rises in one unbroken filament, of the thickness of a slender rod, to the height of twenty feet or more; but the air being greatly condensed, the moment it escapes from the tube its particles exert a lateral repulsion, and, instead of pouring upwards in a uniform slender stream, it spreads out into the form of an inverted cone, in the axis of which, where the rarefaction is great, the ball plays up and down. So securely is the ball confined by the conical shell of air which invests it, that the vessel may be inclined at an angle of 30 or 40 degrees, or carried about freely in the hand, without the ball falling off. The experiment has, in fact, something of a magical effect; for, when viewed at the distance of three or four yards, so that the whizzing noise of the air is not heard, the ball seems to leap and play, and attach itself to the vessel by some secret and invisible power of its own.-Scotsman.

PROCESS FOR RENDERING LEATHER, CANVAS, LINEN, AND OTHER ARTICLES WATER-PROOF.

By MM. Farrimann and Thilly. TAKE 100lb. of the best linseed oil, add 14lb. of acetate of lead, 14lb. of calcined umber, 1lb. of white lead, and 1lb. of very finely-powdered pumice-stone. These solid substances, well ground and mixed together, must be boiled in the oil for ten hours, over a moderate fire, to prevent the oil from burning. This varnish should be of such a consistence, that, when mixed with a third part of its weight of pipeclay, it will be as thick as treacle. It is left to settle eight days, and is then passed through a lawn sieve. The next process is, to grind,

in a solution of strong and clear glue, as much pipe-clay as amounts in weight to the tenth part of the oil employed, aud to mix it to the consistence of ointment; adding the varnish by degrees, and stirring it well with a wooden spatula. This varnish must be repeatedly stirred till it becomes perfectly fluid, and then the desired tint is given by adding a fourth part of the colour, ground in oil.

The linen must be stretched upon a wooden frame, and the composition applied upon it with a large spatula, three inches broad and nine inches long. The frame is then inverted, and the operation repeated upon the other side of the cloth it is then left to dry for a week, and separated from the frame for use.

This cloth may be used for ridinghoods, covers for carriages, &c. &c.

For leather and skins the same composition is used; but to give the surface a smooth and brilliant appearance, the following varnish is employed:-Take 5lb. of the oil varnish, and an equal weight of well clarified resin; boil them together until the resin is dissolved; then add 2lb. of oil of turpentine, having the colour to be given to the varnish ground with it, and passed through a lawn sieve. This varnish is to be applied with a brush. When the varnish is thoroughly dry, it must be rubbed

even with a pumice-stone and water, and be then washed clean. Two or three coats of varnish being then applied, and each coat suffered to dry for two or three days, is sufficient to produce a brilliancy equal to that of the japan lacker.— Mechanic's Magazine.

TO CORRESPONDENTS. PUBLICUS ARTIUM AMICUS has been received. His list of errata, as fur as it is correct, shall be inserted at the end of the Volume. We have no doubt the two Works he recommends to us as models may be superior to our own; but, unfortunately, one of them is, we believe, dead, and the other dying. Does our WELL WISHER wish us to follow this part of their example? His advice would have been still more valuable had the postage been paid; and unless this is done in future, his communications cannot be received.

J. Williams, E.D...y, and W.W. all came to hand too late for insertion, or to be satisfactorily answered in the present Number. They shall all be attended to next week. E. D.. y is informed, however, that the hints will be attended to; and that we cannot learn when the second Part of the book alluded to is to be published.

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