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bent out horizontally at g, in order to hold the coloured indicator lamp h, and let it swing freely. The end e is made heavy enough to bring the lamp h perpendicular over the centre light, whenever it is left at liberty so to do. Therefore, to indicate a right or left course, the arm & must be pulled aside; for this purpose two smaller arms, i and j, project from the arm d, having lines k and I fastened to them, fig. 1; these pass through the guiderings m m and descend to the deck or to the captain's station.

In fig. 2, the arm d is at liberty; it therefore stands perpendicular: but in fig. 1 it is pulled aside by the line k to the position that indicates helm starboard. The captain, by working the lines, k, and 7, informs the vessels ahead what course he is steering, and also indicates to the steersman how he is to put the helm, without the necessity of speaking to him, the back of the lantern being perforated with small holes, through which light enough passes to enable the helmsman to see their position. Fig. 2. Ibid.

Fig. 1.

Helm
Steady.

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The thanks of the Society were voted to J. L. Fenner, Esq., for the following communication describing a very simple and effectual method of applying the cupping glass.

March 6, 1839.

Sir, I beg to submit to the Society of Arts my invention to render the operation of cupping (whether with the scarificator or as dry cupping) so simple, that the due exhaustion of the glass-the only point of difficultymay be readily accomplished by any one with unerring certainty, and without the possibility of any accident. I have found, in my practice, that the application of the exhausted glass (dry cupping) has proved a new source of relief in a variety of diseases, especially the neuralgic, to which the effect of most embrocations and liniments bears no comparison. A far greater number of diseases are relieved by dry cupping than by the scarificator; and it has often proved an excellent substitute for a more painful blister. The true reason why such an important means of relief has been kept out

of sight by the profession is, that as medical men seldom practice cupping, they do not acquire the requisite legerdemain dexterity with the spirit lamp; and, therefore, the expensive attendance of a professional cupper is necessary. My patients, after once witnessing my mode of exhausting the glass, are in the habit of dry cupping themselves a triumph of efficient simplicity which no other mode of cupping could ever boast.

Mr. Clarke's ingenious invention for exhausting the cupping glass, which the Society rewarded, answers very well, and is highly creditable to the inventor. What is the reason that it is not in use? Merely from the additional expense of the sets of silver springs to each variety of glass. Those who do not use the spirit lamp resort to the bungling substitute of lighted tow or paper. For the above reasons, cupping is seldom employed by medical men.

My invention removes every obstacle to its general adoption, and is equally cheap, simple, and efficient. I attach a shred of dry lint, or linen, to the bottom of any kind of cupping glass (or, on emergency, to some forms of tumblers or wine glasses) by means of a moistened wafer. A very little spirit of wine is dropped on the lint, and ignited, the mouth of the glass being held downward, so as just to keep the flame burning until brought close to the part to which it is about to be applied. Next, the mouth of the glass is raised so as to allow the spirit to flare up for an instant; then the mouth is to be held downward, and when the flame recedes within the edge, the glass is to be quickly applied to the skin, when it will be found to be duly and satisfactorily exhausted.

I have now two delicate ladies under medical treatment, who have been signally benefitted by dry cupping; each, after only once witnessing the operation, performed it on herself the next and successive times. One of them, dispensing with the assistance of vision, on one occasion, applied the exhausted glass to her back, and kept it on more than an hour.

J. L. FENNER.

1bid.

Newly Invented Gas Light.

On Wednesday, 13th May, the Count de Val Marino, the inventor of a new description of gas, for which he has obtained a patent, explained the nature of his invention, and exhibited the apparatus by which it is carried into effect, in the presence of his royal highness the Duke of Cambridge, the Marquis of Douro, Lord R. Grosvenor, Lord C. Somerset, Sir F. Trench, and several other distinguished and scientific persons, who assembled for the purpose in a building attached to the workhouse, in Mount street, Grosvenor square, where the apparatus is now erected, with the view, it is understood, of the gas being used experimentally in some of the streets in the parish. In order to compare the patent gas with that now in use, three lamp posts have been erected at the top of John street, Berkeley square; one of them is lighted with the ordinary gas supplied by one of the public companies, another, having a burner of precisely the same description with the first, is supplied with the patent gas, while the third is not only lighted with the new gas, but is furnished also with a burner invented by the Count de Val Marino.

The apparatus for preparing this new gas was temporarily fitted up for this occasion, and the manner in which the gas is generated was explained in a very satisfactory manner to his royal highness and the company by the

Count de Val Marino, who speaks only in the French language. He pointed out the particular construction of the furnace, and its arrangements in the following manner, as nearly as we could collect the facts:-There are three cylindrical retorts placed vertically side by side, and inclosed in a furnace of suitable dimensions to heat them up to what is technically called a red white heat. This is obtained in a short time, with but a trifling cost for fuel. The requisite heat having been obtained, water is allowed to drop rapidly, but not to stream, into the first retort, and tar into the third one. We must here observe, that the three retorts are charged with coke broken into pieces about the size of a walnut. In the first retort the water is decomposed, the hydrogen is separated from the oxygen, which, uniting with a certain portion of carbonized vapour, produces carbonic acid gas. This product, with the liberated hydrogen, now passes into the second retort, and it is in this retort that the carbonic acid gas is changed into oxyde of carbon by passing through the heated interstices of the coke. The liberated hydrogen, with the other products, unite in the third retort with the superabundance of carbon which is produced by the decomposition of the tar, and thus is formed a pure carburetted hydrogen gas, not requiring any further purification.

The proportions of the water and tar to each other for producing the purest and strongest gas, are, three parts of the former to one part of the latter substance-consequently, the materials being very cheap, the product cannot bear any great price.

This gas seems to be a very active and powerful agent, as it appeared in juxtaposition with the common gas, and when carefully prepared, the flame it produces is clearer, and consequently more bright, than the same surface of the ordinary gas, and there are street lamps lighted from eight to nine o'clock in the evening in the street at the rear of the workhouse looking into Hill street, where the qualities of the two gases can be accurately compared.

Lond. Journ.

Self-acting Safety Brake, for bringing up Railway Carriages with Ease and Expedition.

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Q TF Q

F

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Sir, I need not inform the scientific portion of your readers, that a surer and more expeditious method of bringing up railway trains, whilst traveling at high velocities, in cases of emergency, has been a deficiency long felt by those connected with locomotive machinery, and which the following plan will, I think, adequately supply.

Here it will be at once seen, that the old enemy, who hitherto has stared us full in the face, is converted into a friend of no ordinary worth, if there be any truth in the old saw, "a friend in need is a friend indeed."

Supposing a railway train to be traveling at a great velocity, the steam sudVOL. XXVI.-No. 3.-SEPTEMBER, 1840.

17

denly cut off, and a powerful manumotive brake applied to both engine and tender alone, the sudden check will cause the whole train to rush together with considerable violence. Now this property of the carriages rushing upon one another, is converted into the stopping power, or agent, the carriage following, acting upon the brake of the carriage in advance.

The prefixed figure is the carriage in advance, having the new brake attached: the near wheels are removed for bringing the parts into view.

B, B, are the brakes faced with wood, turning upon their centres, Q, Q; C, a curved spring for releasing the brakes, and strong enough to resist the required pressure; T, a knee joint turning freely upon the centres, T, D, E, to which is attached a bar, G, to which latter bar is attached the lever, L, having its fulcrum at Z. Power is to be applied at W, which is depressed by the inclined plane, P, of the following carriage running upon it; W, a roller the breadth of the carriage.

It will be seen from the above plan, that each carriage can be fitted with eight brakes, so that in a train of twelve carriages (the brakes on the last carriage being idle) we should have no fewer than eighty-eight brakes ready for action in an instant, and under the immediate control of the engineman and assistants, with the amount of stopping power always coinciding with the inomentum of the moving train. Manchester, May 25, 1840.

Yours, &c.

Improvement in Mr. Smee's Galvanic Battery.

WM. JONES.
Lond. Mech. Mag.

Sir, the very superior galvanic battery recently discovered by Mr. Smee, in which platina is precipitated upon silver, or copper plated with silver, suggested to me the trial of another metal in the place of silver; but before I give an account of these experiments, permit me to state, that since the appearance of your Magazine containing the directions for making Mr. Smee's batteries, I have had one made and tested it. It consists of 24 silver plates, size 7 by 10 inches, divided into six elements or pairs, and although finished but a few days since, I have kept it almost constantly in action, and its effect, as compared with the old batteries, far exceeds the most sanguine expectations I had formed of it.

The expense of the plates was great, and recollecting, while preparing them, that iron immersed in a solution of sulphate of copper, without any previous preparation, almost instantly becomes coated with that metal, the experiment was made with iron in nitro-muriate of platina. To my surprise, a coating of platina formed on the iron almost immediately, and with much greater facility than on the silver plates. In consequence, a battery has been made of 20 small iron plates, platinized, of about 2 inches by 3 in size, and the result is a power every way equal to a battery of silver plates. The process is in both cases the same, except the washing the plates with nitric acid previous to platinizing; but the iron does not require one-half the time to prepare it that is required by the silver.

Apart from the comparative cheapness of this battery, many other advantages may be mentioned. In using silver, it being susceptible of action from the mercury used in amalgamating the zinc plates, the electric action projects some particles of mercury from the zinc upon the silver plates, and from this cause their action and effect gradually diminish. Iron having less affinity for the mercury than the zinc, is not attacked by it, and no perceptible diminution of its effect or action takes place for hours, and after repeated trials of some

hours each, is found to be as good as at the first immersion. The acid used is the same as directed by Mr. Smee, viz. one part sulphuric to seven parts of water. No porous tubes, canvas or paper bags or sacks, are required to preserve the platina.

I have now in progress a large battery of thirty iron plates to be divided into six elements, or pairs, my object being quantity rather than intensity. I need not dwell upon the advantages this discovery offers in regard to its cheapness, its freedom from noxious gases, or its equal and constant action. I have only ventured this communication in the hope that others possessing greater experience, science, and opportunity than myself, may make still further and more important discoveries.

I am convinced that the iron battery, from its many advantages, is an important step towards the adaptation of electro-magnetism to useful mechanical, as well as chemical and scientific purposes.

Paris, May 31, 1840.

I remain, Sir, your obedient servant,
JAMES H. PATERSON.

Ibid.

Rain Gauges.

Sir,-In turning over the pages of your useful miscellany, I find at page 163, vol. viii., the following method of constructing a rain gauge:

"Take a funnel whose opening is exactly ten square inches, and fix it in a bottle; as the rain descends it will fall into the funnel, and from thence into the collecting vessel. The quantity of rain caught is ascertained by multiplying the weight in ounces by .173, which gives the depth in inches and parts of an inch."

This rule will be limited in its usefulness from the circumstance that parties wishing to construct such a gauge may not be able to command a funnel the area of whose opening is precisely ten inches. How many shops may require to be searched before one can be found, or who will undertake to make one, the diameter of whose opening shall be 3.568 inches? In these circumstances, it occurs to me, that a method of finding a multiplier adapted to any other area of funnel may be acceptable. If you are of the same mind, I shall feel obliged by your giving insertion to the following:

area.

Let d the diameter of the opening of the funnel; then will d2 x.7854 = its Also, let a= the altitude of the column of rain fallen; then will its contents, or the quantity received by the funnel, be expressed by a d2x.7854. Now, a cubic foot, or 1728 cubic inches of water weighs 1000 ounces avoirdupois. Therefore, to find the weight of the quantity of rain received by the funnel, we have the following analogy:

1728: ad2 X.7854 1000: ad2 X.454. That is, calling the weight w, ad2 X.454-w. Whence, a=- w

d2 X.454

2.2 = w X d2

Hence, the rule is,

divide the constant quantity 2.2 by the square of the diameter of the funnel; the quotient will be a number by which, if the weight in ounces of the rain in the receiving vessel be multiplied, the product will be the height in inches of the column of rain fallen.

This multiplier once found, it will be advisable to inscribe it on a conspicu. ous part of the funnel to which it corresponds.

To exemplify the rule, I may give an example: suppose the diameter of the

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