a lamp, and a coal fire." But I ask, whether it be possible to obtain carbon from tallow, without that carbon is first caused to exist in a state of gas, and in chemical union with hydrogen?

"To return to what I consider the chief difficulty of the subject: in the flame of alcohol may be distinctly observed the appearance of two flames; the inner one is sometimes white and luminous (from the presence of carbon), the outer one is blue, and in some cases appears full of an inch in depth. A third flame, of an orange colour, may be produced by making the alcohol boil with a red hot wire, and the question is, how does the oxygen get to the inner flame?

The flame of a candle is another instance, as it appears to be enveloped with a thin sheet of blue flame, extending to about 3ds of its height. How then does the oxygen get through this thin flame, to supply the carbon which exhibits such a brilliant combustion beneath? This Mr. Rutter has not attempted to explain.

The flame produced by the combustion of an explosive mixture (oxygen and hydrogen), through a small aperture, has always appeared to me a singular circumstance; for the explosion of a large volume of the mixed gases is so instantaneous, that reasoning from this fact, we might expect to find the flame extending no more than an eighth of an inch from the jet, though, on experiment, we find the flame several inches in length. The explanation of this appears to me as follows:-When the gas, as it issues rapidly from the jet, is first lighted, an instantaneous union takes place, and water is formed, which, owing to the heat, immediately becomes vapour; but as this vapour is not instantly removed, the next portion of gases is so mixed with it that the quickness of their union is prevented, the vapour impeding the passage of the particles, one to the other, and perhaps destroying in some measure 'their attractive force. Now in this union there are three substances present, and, I believe, that the more substances the slower must be the union, as the particles and different attractions must interfere with one another. Now, in the case of a candle, four substances are present in the flame, viz., oxygen, hydrogen, aqueous vapour, and carbon. The thin film

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of blue flame, at the outer surface, I consider to be hydrogen; this attracts oxygen from the air, but owing to the aqueous vapour the union is not instantaneous; and the attraction of carbon for oxygen being very great, at that high temperature, enables it to seize some of the oxygen attracted by the hydrogen. If this be the right explanation, we can account for the sudden union of gases in an explosive mixture of oxygen and hydrogen, for the particles are not impeded in their attractions, and consequently their union, as we find by experiment, is almost instantaneous. Explosive mixtures of oxygen and hydrogen combine with much greater violence than explosive mixtures of oxygen and carburetted hydrogen; the different attractions of the carbon and hydrogen, in the latter case, interfering in some measure with that rapidity of union which takes place when only two substances are present. How brilliant is the combustion of those substances in oxygen gas where solids are formed by the union, such as phosphorus and the metals! This is, doubtless, owing to the rapidity with which the phosphoric acid, on the metallic oxide, gets out of the way, so as not to impede the union of fresh portions of the two substances. How much again the union of carbon with oxygen is impeded by the formation of carbonic acid! Remove this as quickly as formed, by urging a stream of air on the burning substance, and intense chemical union then takes place. On the same principle, lecturers on che mistry might exhibit their experiments to much greater advantage than they do at present, by urging a stream of oxygen upon red hot metals, or burning phosphorus, &c. &c. Chemical action would then be in perfection, and appear more brilliant and intense than by the mode usually adopted.

I now beg leave to notice Mr. Rutter's reply to my letter. Mr. Rutter cannot conceive the possibility of aqueous vapour being projected into the interior of flame; how then is it projected from flame? The vapour, when formed, expands in every direction alike, and consequently is projected into the flame, that is, among the particles of carbon. The velocity of the expanded vapour is no doubt very great, owing to the extreme heat to which

254

it is subjected on its first formation, and the vaporous current, Mr. Rutter speaks of, moves so slowly in comparison, as not much to affect it. Mr. Rutter cannot understand those mysterious movements in the flame of a candle which I mention, and says," Moreover, the theory of combustion as exhibited in a candle, is perfectly intelligible, without having recourse to any such rapid movements" as are hinted at by your humble servant. Now, Mr. Rutter will oblige me, and, no doubt, many others of your readers, by making this difficult subject perfectly intelligible. The numerous experiments related by that gentleman, together with his remarks and conclusions, cannot fail of being interesting and instructive to all who read them; but the simple, or rather the complex, phenomena presented in the flame of a candle, will require further consideration and reflection, before they are made to appear in such a way as to be" perfectly intelligible."

It is hardly necessary for me to say any more as to the burning of coal-tar, since my design was merely to show how it might be done, and had no reference to the "cost of the process." At present I pass over Mr. Rutter's explanation of the obscure paragraph, as well as his theory of the combustion of coal-tar and water, which I can hardly agree to. I will send you my ideas at some future period, when I have given the subject more consideration. It is not an easy thing to exhibit the luminosity of heated air, but I think there are some grounds for supposing that it would be slightly luminous when sufficiently heated. The air escaping from the chimneys of some furnaces appears at night as a luminous column, though it may be objected that the light is derived from the fire, and refracted by the air. That the surfaces of boilers are sometimes red hot, may be ascertained in boilers that are much forced, by looking through a hole in the flue, when the fire is burning clear; this is where I have seen indications of a red heat another proof is that the carbon adhering to the metal when the fire is first lighted, disappears when the fire burns violently and the water begins to boil. I remain, Sir, Yours respectfully, WILLIAM WITTY.

London, July 4, 1831.

COMPOSITION OF CHINESE GONGS.

In the Annales de Chimie there is the following account of the Chinese process of manufacturing gongs and cymbals, translated by M. St. Julien, from the "Teen-kong-kae-weh," a Chinese Encyclopædia of Arts and Manufactures:

*

"The red copper used in making musical instruments must be alloyed with mountain tin, which does not contain a particle (literally a vapour) of lead. In order to make gongs, &c., 8lbs. of copper are alloyed with 2 lbs. of tin. If you wish to make little bells or cymbals, the red copper and the tin must be much purer and finer than for gongs.

"When a gong is to be made, it must not be cast in the form it is to have, and then forged with the hammer. You must begin by founding a thick sheet of metal, which must be cut round, and then beaten with the hammer. For this last purpose the round. sheet of metal must be spread upon the ground; and if the instrument is required to be of large size, four or five workmen must be placed around to hammer it. The sheet will spread out and enlarge under the hammer, and its edges will rise up. Then the instrument will begin to emit sounds resembling those of a musical cord. All these sounds proceed from the points which the hammer has struck (literally from the points struck by the cold hammer). In the centre of this drum of copper a boss or round ele vation is formed, which is struck, and the blows of the hammer give it the tone. Two tones are distinguished in the gong-the male tone and the female tone. Both depend upon the rising being less or greater than ought to be given, with rigorous exactness to the boss, according as one or other is desired. By doubling the blows of the hammer, the instrument acquires a grave tone."

M. D'Arcet, in a note upon this translation, observes :

"The only thing I find correct in this account is the composition of the alloy, of which the Chinese author states these instruments are formed. I have analysed seven gongs and twenty-two cymbals, and I have always found in one hundred parts about eighty of copper and twenty of tin. It is true, about five or six years ago, an original letter was communicated to me from a missionary, which stated that gongs contained, besides copper and tin, 8 of bismuth; but the properties of this alloy, and the result of the analyses just mentioned,

* The Chinese have two sorts of tin, mountain tin and river tin; both are found in the provinces of Kwang-see.

show that the workman deceived the missionary on this point. I regard, then, as a fact proved, that these gongs and cymbals are composed of an alloy formed with eighty parts copper and twenty tin; but this is far from sufficient to enable us to fabricate these instruments; for this alloy is as brittle as glass, and if it be used as it comes from the crucible, it would be not only impossible to forge it, but even to use such instruments, merely cast with this alloy without their breaking. This happened to an untempered gong, which was made at the school of Châlons for the King of Prussia, and to the gong at the opera, which, being cracked, was heated in order that it might be mended with silver solder. The alloy of eighty parts copper and twenty of tin is so brittle, especially when hot, that it may be reduced to powder. This alloy has great density; its grain is very fine, and its fracture almost as white as that of bell-metal. Chinese gongs and cymbals, on the contrary, have a small specific gravity, and a fibrous fracture exhibiting the colour of the alloy of ninety parts copper and ten tin, used for cannon. Fragments of gongs and cymbals, far from breaking under the pestle, are malleable, and may, moreover, be bent till the two sides of the piece form together an angle of 1300 or 140o, without breaking. It follows clearly from this comparison, that gongs and cymbals cannot be fabricated, as the Chinese author pretends; that it is only by means of some peculiar process, some sleight of hand, that an alloy of eighty parts copper and twenty tin can be employed in this manufacture. The secret consists in tempering the alloy; in fact, when heated to a dull cherry-red, and plunged into cold water, it takes instantly all the physical characters of the gong and cymbals. I have manufactured by this process upwards of sixty pairs of cymbals, and experience has fully justified what I have stated.

All

"Nothing is said in the Chinese account about tempering, yet, without this operation, it is impossible to fabricate these articles. As to the mode of making them, the alloy of eighty parts copper and twenty tin, even when tempered, cannot possibly be forced, and especially beaten out. the Chinese author says about casting the alloy in the form of a plate, and beating it out with the hammer, is a mere fiction imposed upon him by a Chinese artificer, just as our artificers endeavour to mislead curious visiters in our manufactories. The following method is in my opinion the true

one:→

"The model of the instrument is forged in red copper or brass. To this model is given exactly all the desired forms, by making the face of the hammer penetrate more or less on the two surfaces, so as to

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form that continuity of spherical hollows and salient parts we see upon cymbals, and especially gongs. When the model is finished it is employed to make a mould in sand, in putty, or in metal. An alloy of eighty parts pure copper, and twenty of fine tin, is prepared, which is run into an ingot; it is then re-cast, and run into the mould. The piece when taken out of the mould is roughscraped; it is tempered as is done with steel. If it is mis shapen, by plunging it red hot into cold water, the shape may be rectified by the hammer, and by flattening it with gentle blows. The required tone may be given either at first by forcing the temper more or less, or afterwards by hammering. It is polished by means of a lathe, as is done with saucepans of copper or brass, and the instrument is finished."-Asiatic Journal.

NEW APPARATUS FOR RAISING SUNKEN

VESSELS.

Sir, I have invented an apparatus for raising sunken vessels, which I believe to be different from any yet known, and have made a model thereof. From the trials which have been made, it appears that the apparatus would be exceedingly manageable. It would possess great buoyant powers, and be easily connected to the sunken vessels; the operation could be uninterruptedly continued during the ebbing and flowing of the tides; and the sunken vessel could be raised from any depth to which a diving-bell can, with safety

to the lives of the men inside, be lowered. Two or three would suffice for the whole kingdom, and would cost about 1,000l. each.

I am sorry to say that I have not myself the means of carrying this plan into execution; neither am I acquainted with any inflaential persons who might take it under their patronage. I address, therefore, this notice to you, in the hope that, if you will favour it with a corner in your valuable Journal, it may catch the eye of some gentleman who would be disposed, for a share in the profits of the invention, to assist in bringing it into public notice. I am, Sir,

Yours most obediently,

London, July 3, 1834.

A. B.

[Any letter for the writer, addressed to the care of the publisher of the Mechanics' Magazine, will be duly forwarded.]

NOTES AND NOTICES.

A Parliamentary Committee has been appointed to investigate the claims of Mr. Coldsworthy Gurney to a reward from the nation, for his efforts to introduce steam-carriages on common roads. It may now, therefore, be expected that "the whole truth," with respect to Sir Charles Dance's famous experiment on the Gloucester and Cheltenham road, will at length come out. It will be remem

bered that Colonel Macerone has asserted, without, as far as we are aware, any contradiction from the parties interested, that, while the public were led to believe that only one carriage was employed, it in reality required three to keep up the journeys without intermission-of course, at a ruinous expense. The members of the new committee will do well to sift the evidence that comes before them thoroughly, if they would avoid the risk of exposure to that censure, for undue precipitation, which has been incurred by the former committee on the subject; especially as, on the present occa sion, a part of their duty is to hold the public' purse-strings. If speculators, who have missed their aim, be encouraged to go to Parliament for 66 compensation," there will soon be no end to their

"claims."

It is probably very little known, that an extensive manufacture is carried on in this neighbourhood by which old rags are made into new cloth: yet such is the fact, and to so great an extent, that at least 5,000,000 lbs. weight of woollen rags are yearly imported from Germany, and other parts, for this purpose. The rags are subjected to a machine which tears them in pieces, and reduces thein to nearly their primitive state of wool; and they are then, with a small admixture of new wool, again carded, slubbed, spun, and woven, and they make a cloth not very strong, but answering very well for paddings, shoddies, and other similar purposes. The manufacture is carried on chiefly in the neighbourhood of Batley.-Leeds Mercury.

The Book Trade in India.-The profit obtained upon books is more moderate than that of any other European commodity, the retail prices being entirely regulated by those of the London market -rupees are reckoned for shillings.

A book

which is sold at the publishers at home for a pound, is charged at twenty rupees in Calcutta; and considering the cost of freight and insurance, the perishable nature of the commodity, and the very great care requisite to secure both leaves and binding from being injured by damp, or devoured by insects, the price cannot be considered high. Books intended for sale must be carefully taken down from the shelf and wiped every day, and not only the outside, but the interior also must be carefully examined: a work of time, which, in a large establishment, will occupy a great number of servants. The warping of splendid bindings in hot weather, and the rusts and mildews of the rainy season must be taken into account, while the white ants, being no respecters of engravings, notwithstanding the greatest care, a hiatus will sometimes be visible in the centre of some superb specimen of the art, from the burin of Finden, Heath, or others of equal celebrity.-Sketches of Indian Society.-Asiatic Journal.

It speaks little for the sympathy of the Commons' House for the common people, that they have recently passed a resolution to allow the ploughingup of footpaths passing through fields. There is, even at present, too great a facility for stopping up public footways, but if this resolution be agreed to finally, it is to be feared that it will prove their complete destruction.

The City improvements, near the Bank, are now proceeding with considerable spirit. The houses which so long made Princes street a narrow alley, are now pulled down; and we believe some progress is already making in the intended line of straight street from thence to the bottom of the City-road, so that the great desideratum of a direct thoroughfare through the heart of the City, bids fair to be soon accomplished. The line in continuation from the Mansion-house to London-bridge, is proceeding in a very slow but sure style.

Metropolis Road Locomotives.-Within the last few days preparations have been making, on the line from the City to Islington, for another "start"

A Steam Fleet.-Her Majesty, in her late trip down the river, on her way to Germany, was accompanied by no less than twenty steam-packets. The sailing vessels were quite eclipsed, for wind and tide being contrary, not one of them could join convoy,-except, indeed, Sir William Curtis's, and that was taken in tow by a steamer.

Among the modes of overland communication with India, one is to be noticed which has been some time set on foot under the direction of Mr. Rob. Todd, a British merchant established at Damascus, and who has also a house at Bagdad. He has organised a line of couriers from Damascus to Bagdad and Bussorah, aided by Colonel Taylor, the British resident at the latter places, and with the concurrence of the present authorities in Syria. Once every twenty days a courier is despatched from Damascus, who performs the journey to Bussorah in from 16 to 23 days; and from Bussorah the despatches are forwarded by the first vessel for Bombay. On the European side the line is thus completed: from London to Constantinople by the ordinary post, 27 to 30 days, or by express, from 16 to 18-from Constantinople to Aleppo by Government Tartars, 15-and from Aleppo to Damascus, 6 or 7. The time occupied by the land journey is about 74 days in all, to which there is to be added, the length of the voyage from Bussorah to Bombay.-Abridged from the Times.

We think our correspondent S. F. has entirely misconceived the scope of the playful account given in our last number, by G. C., of "two certain plans of perpetual motion." The object of the writer seems to have been to impress on the minds of young mechanicians the folly of wasting their time in vain endeavours to render the effects of causes greater than the causes themselves; or, in other words, to gain power out of nothing-a process without limit or value, were it not cut short by the want of all limit to its folly; and this he could not, perhaps, have done in any way so well, as by exhibiting a couple of infallible perpetual movers that would not stir at all, though they bade as fair for it as any of their kindred. We may take this opportunity of pointing out a verbal misprint in the article alluded to, which renders the meaning in one part rather obscure. In the 6th line, the word "curve" has been erroneously substituted for "cause."

Communications received from J. P. T. (omitted to be acknowledged last week)-Mr. Isaac Howe -Mr. Foord-Mr. H. C. Calhoun-Mr. Marrs (answered by post)-S. P. M.

Erratum.

In the title to the map, No. 567, for "ASIA," read "AFRICA.' "

The Supplement to Vol. XX., with a Portrait of William Symington, is now ready, price 6d. also Vol. XX., complete, in boards, price Ss.

LONDON: Published by M. SALMON, at the Mechanics' Magazine Office, No. 6, Peterborough Court, between 135 and 136, Fleet-street. Agent for the American Edition, Mr. O. Rici, 12, Red Lion square. Sold by G. G. BENNIS, 55, Rue Neuve, Saint Augustin, Paris.

M, SALMON, Printer, Fleet-street.