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172

FORCE EXERTED IN ARCHERY.

rapid transition of solid matter to the gaseous form, and in the next instant spring majestically to the skies! Armed with the exercise of a similar agency, the miner, too, might rend with facility and tremendous effect vast aggregations of the rocky impediment which now speaks a bold defiance to his most vigorous efforts, even when seconded by the happiest expedients of the most consummate genius in science; and, alas! it might moreover be anticipated, that the deadly engines with which kings and tyrants are wont, at the suggestion of hirelings and slaves, to arm the hand of man against his fellow man, would derive from the sacred influence of philosophy an accession to their destructive and inhuman power.

The consummation of events like these may now be viewed with doubt, and their suggestion receive the sneers of derision; but they are, notwithstanding, within the scope of possibility, and, ranking in alliance with undertakings of equal grandeur, originating in analogous means, will, doubtless, constitute a feature in the progressive advancement of future science.

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Then let D E be the direction of the force exerted by the left hand, as in the ordinary way of shooting; then, if the bow be held by the left hand, and the weight C of 50 lbs. applied, it is very evident that a force of 50 lbs. is exerted with the left hand only, for it has to support the 50lbs. ; and 50 lbs. supported by the left hand, and 50 lbs. pulling in the opposite direction F C, will make 100 lbs. Now, let the weight C be removed, and the right hand applied to the point F, in the direction FC, and let it draw the bow-line to the same extent as the 50 lbs. weight did. A force of 50 lbs. is now exerted with each hand, in opposite directions; for the left hand may be said to support a weight of 50 lbs., and the right hand also exerts a force of 50 lbs. to pull the line to the same extent as did the weight C of 50 lbs.

I am, sir, yours truly,
J. L.,

A young Mechanic.

KNELLER'S PATENT PROCESS OF EVAPO

RATION.

A patent was granted to Mr. Wm. Godfrey Kneller, of Mitcham, chemist, on the 24th August last, for "certain improvements in evaporation." We extract the following particulars of these improvements from the patentee's specification.

Mr. Godfrey first effects a sudden compression of common atmospheric air, and then conveys volumes of this com pressed air," by means of inverted moveable chambers, or ventilators," beneath the surface of the heated fluids or liquids to be evaporated; when these volumes of air, "becoming suddenly expanded by the heat of the said fluids or liquids, pass underneath the lower edges of the said inverted chambers, into the adjoining chambers, and pass off through holes or apertures provided in the upper parts of the said chambers, and through the superincumbent fluids or liquids, loaded with the aqueous or other vapours." On" these chambers or ventilators being raised or elevated above the surface of the said fluids or liquids, they again become filled with fresh air, which

RUSSIA LEATHER-CONTRACTION OF CAST IRON.

is also in its turn conveyed beneath the surface of the fluids or liquids by a repetition of the movement of the ventilators." In this way a continual and rapid evaporation" of the heated liquids. is stated to be produced; and it is to be inferred, from the process being made the subject of a patent, that the patentee considers it superior in these respects to every other previously in use. We have heard that it has been applied by Mr. Kneller to the evaporation of brine, with a degree of success which would fully justify such a conclusion.

Mr. Kneller does not claim as his in

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173

with tar extracted from the birch tree. This is also erroneous; for I can assert, from long observation, that the tanners universally use willow bark,

The process of curing the leather used by bookbinders, is kept as much as possible a secret by the Russian tanners; but from all I can hear, and from every observation I bave been able to make, (and I have been both curious and inquisitive on the subject for many years,) I believe the peculiar smell arises from the length of time taken to prepare the hides, (called in England, I think, felling,) before they are put into the tan. The leather never acquires the smell under a two years' process.

There is a kind of leather called Chorney Werostock, (of which I also send you a specimen,) used by the lower classes here for making boots, &c., and which is made water proof by a composition, in which there is a mixture of some kind of tar or rosin; but I can confidently state, that nothing of the kind is used in preparing the leather for the use of bookbinders.

Trusting the foregoing information may prove acceptable to your readers, I remain respectfully yours,

St. Petersburgh, 8th May, 1834.

J. K.

[The specimens of leather obligingly forwarded with the preceding communication may be in spected at our office.-ED. M. M.]

EXPERIMENTS ON THE CONTRACTION
OF CAST IRON BY FROST. BY MR. W.
REED.

Sir, I send you some observations on the contraction of cast iron in Russia by frost.

Dur

In the summer of 1832 I had a threethrowed crank to turn, with four bearings. After the crank parts were turned, I filled them up with dry beech, to stiffen the work for turning the bearings, and left it in this state in the lathe. ing the following winter, one sharp frosty night, it fell out of its centers. I saw that nothing could have touched it; for there was a slight covering of snow over it, which had remained the same for some days, and there was no foot mark near.

The summer following I procured a cast iron shaft, ten feet long, six sided,

174

MARYLEBONE LITERARY AND SCIENTIFIC INSTITUTION.

and three inches diameter throughout. I then took a dry fir straight-edge, twelve feet long, one inch thick, and four inches wide, which had been in use ten or twelve years, and was of course well seasoned, and on this I screwed two brackets, so as to feel that they touched each end of the ten feet shaft. When these dimensions were taken the thermometer in the shade stood at 14°. Reaum. (63° Fahr.) Last winter I had this shaft removed out of doors, and laid on two bricks, that it might be the more readily measured, and the frost have a better chance of acting on it. After the frost had set in some time, and when the thermometer was

- 140. Reaum.-making altogether a difference of 28 degrees-the contraction was one-tenth of an inch in the ten feet. I measured it again next morning, and found the contraction to be exactly the same.

Now, to have an idea of the practical importance of such a degree of contraction as this, we have but to consider that one-tenth of an inch in ten feet is equal to one inch in every 100 feet, or seven inches in an iron structure of the length of Southwark-bridge. Nor should the engineers of your country contemn such a source of danger from a notion that such a degree of cold as-14°. Reaum., is not likely to be experienced in the latitude of England. For in the winter of 1814, when the Thames was frozen over, and there was a fair held upon it, the degree of cold was fully equal to this.*

The iron shaft was again measured, when the cold had increased to 21o, and it was found to have shortened exactly one-eighth of an inch.

The cold here during the past winter has never exceeded 25°; but this is quite enough, since it is sufficient to reach both the water and gas pipes, and to cause immense inconvenience; for if such pipes are once frozen, it is of no use meddling with them till April or May. Even as late as July 4, the frost has been found in the ground four feet below the surface in particular situations. Coal gas condenses at 10 or 12 degrees of frost in out-door situations. A gentleman that has a large establishment in

*The thermometer in England has been observed as low as 2 deg. below zero of Fahr. scale, which is 15% deg. below the zero of Reaum, ED. M. M.

St. Petersburgh, lighted with coal gas told me that he had sad trouble with the lamps at a distance from the building. There are two gas lamps at the principal entrance to the factory where I am employed; the pipe is brought in a slanting downward direction inside the building, and a copper vessel is attached to it by a small cock and screw, to receive any of the gas that may be condensed; but though some condensed gas does find its way into this vessel, the cold is so intense that the pipe is at times frozen up with a solid body of ice to within a foot of the burner, which of course puts out the light. I have taken the copper vessel when thus filled with frozen gas, and put it on a slow fire, where as the liquid evaporated it burned with a yellowish blue flame, sufficient to show that it was hydrogen gas. I am, dear sir, yours truly,

Peterhoff, Jan, 1834.

WM. REED.

MARYLEBONE LITERARY AND SCIENTIFIC
INSTITUTION.

Extract from the Quarterly Report, read to the
Members, May 27, 1834.

"In the short period of one year from its establishment on the present plan, the committee have been enabled to take premises more extensive and commodious than those of any similar institution in the metropolis. They possess already a library of 2,000 volumes, among which are many of the most valuable standard works in the English language, and a reading-room, supplied with ten daily papers, and every periodical work of merit. Classes for the instruction of members in mathematics, chemistry, botany, music, and the French language, have been formed; and lectures are regularly delivered by eminent professors, among whom areSir A. Carlisle, Dr. Lardner, Dr. Copland, Dr. Southwood Smith, Messrs. Hemming, John Taylor, Burnett, Wallis, and M'Culloch.

"The increase in the number of subscribers, during the past quarter, having been greater than that of any preceding quarter (135 new members having joined the institution during that period), induced the committee to make arrangements for a more commodious lecture-room. The negotiations which were then entered into for the purchase of additional ground are now completed, and the erection of a theatre, capable of containing 850 persons, will immediately be commenced."

INQUIRIES.

INQUIRIES.

Electrical Machines.-Sir, I have in my possession a piece of plate glass, out of which I wish to make an electrical plate machine; I have therefore to solicit, through the medium of your valuable Magazine, an answer from some of your numerous mechanical readers, to the following questions. Permit me to add, that I hope they will not for a moment hesitate in imparting to a young inquirer after knowledge, all that information which is essential to the production of a good electrical machine.

1. By what method can I convert an irregular sided piece of glass into a true circle?

2. How is the hole in the centre of the circle to be made; and by what means is the axis by which it is to be turned (when made) secured, so as to be able to turn the glass when four rubbers are pressing rather hard against it?

3. The thickness of the glass is about ths of an inch will this be a sufficient thickness? The utmost size that I can make it, will not be more than 13 inches diameter.

4. Will a machine of that size be powerful enough to perform all the common electrical experiments, such as firing gunpowder, spirits of wine, the thunder-house experiment, &c.? am, &c. J. L.-B********, April 12,

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1834.

Grinding and Polishing.-Sir, There is a piece of information which is very much. wanted, and for which you may look in vain in the large Encyclopædias, namely, the mode of polishing by hand in the small way. I have an idea, that it is the powder of the substances themselves which is rubbed off in the process of grinding, that is employed to give the last exquisite polish; at any rate, it must be so with the diamond.--I am, &c. yours, G. DAKIN.-Dereham, March 3, 1834.

Optical Instruments.-Sir, Can any of your correspondents give me practical directions for constructing a Catadioptrical Phantasmagoria, of which a brief description is given in Dr. Brewster's Natural Magic? Supposing the diameter of the concave mirror to be 9 inches, and its surface nearly flat, I wish to know the size of the box or case, the size and focus of the lens for magnifying the objects, &c. &c.; I have been informed by an optician that the thing is altogether impracticable. I should also like to know what kind of an object glass I must procure for a magic lantern, the plane convex lens or bull-eye being 8 inches diameter and 10 in. focus-I am, &c. J. BATEMAN.

175

Weights and Measures.-Sir, Would you have the kindness to inquire, through the medium of your valuable Magazine, whether the weights in the town of Lincoln are the same as in the other parts of England, and how many pounds butchers' weight go to the stone? By so doing, you would oblige your constant reader, J. P.

Creaking Shoes.-Sir, I am a very nervous and irritable subject, and when employed in my study, am annoyed by the slightest disturbing circumstance, even a whistling wind, or a sudden crack in the furniture; but of all things the most obnoxious to me is the creaking of shoes or boots, either in a room or the street. If any of your readers can inform me of a preventive or remedy, they will confer an everlasting obligation on a real sufferer. I have had recourse to keeping the soles constantly damp, but this is liable to cause a cold by its effects on the feet, and also soon destroys the stitches.-I am, &c. S.S.-Gray's Inn, May 12, 1834.

Ascent of Smoke.-Sir, Is there any state of the atmosphere during which smoke will not ascend; and if so, what is that state, and how does it operate to prevent smoke from ascending? There are times when smoke seems to ascend much less readily than at others, and this I have heard attributed to the "heaviness" of the air. But surely this must be an error. Would not the smoke of

a fire kindled on the top of a high mountain roll downwards instead of ascending; and that, not because the air in such a situation is heavier, but, on the contrary, because it is too light to afford the smoke the requisite support? If it were true that the denser the air, the greater is the difficulty in ascending in it, would not the same principle apply in the case of liquids, and might we not thence expect a cork or a ship to float more buoyantly in fresh water than in salt, contrary to the well-known fact. I trouble you with these queries from having more than once heard the remark made in London, that "the smoke does not ascend to-day, because the air is too heavy." The inhabitants of this city should know something of smoke; but if they are in error touching the cause of its not ascending, I trust that some of your ingenious correspondents will take the trouble to enlighten them. Ex fumo dare lucem, is, I hope, an object not unworthy of the "Mechanics' Magazine," even in a case of so little importance as the present.-Your obedient servant, Z.-April 22, 1834.

Sir,-A subscriber to the Mech. Mag., would be much obliged to any of its ingenious correspondents to inform him, how a square hole is to be filed by a round file?B. T.

176

NOTES AND NOTICES.

NOTES AND NOTICES.

An iron carriage, designed as well for heavy guns as for light field-pieces, has been constructed by order of Marshal Soult, under the direction of Captain Thierry, of the French artillery, and tried in the presence of the officers of that corps stationed at Nevers, when it met with their decided approval. It consists wholly of wrought iron, is much simpler in its construction than the wooden earriages at present used, and is of the same weight. The wheels are likewise of iron, of an elegant and peculiarly light make, cost less than any wooden wheels, and may be promptly repaired on the spot when injured. The avant train" is of the same material as the carriage, and bears a munition box of wrought iron, modelled on a similar principle to the vessels for water used in the French navy. An apparatus of greased leather encloses the box, and renders it impenetrable to moisture. By means of a mechanical power, derived from a simple iron lever, the carriage is arrested on the chassis, after its recoil, at a convenient distance for reloading. After this last operation, the mechanical check is removed, and the carriage descends to its proper position in battery by its own action, with a uniform motion, and without manual labour. Captain Thierry has also so arranged the construction of the chassis, which is made of iron, as without exposing it to too severe a strain, has enabled him' effectually to master the recoil of the piece, and within far narrower bounds than can be set in the

case of any wooden carriage. With a charge equal to one half of the weight of the ball, and after simply moistening the chassis, the recoil has never exceeded one metre and forty cents (55,26 inches).—United Service Journal.

The House of Commons has, on the motion of Mr. Chas. Grant, appointed a Select Committee to inquire into the best means of promoting steam communication with India. The Messrs. Seaward, of the Canal Iron Works, in a pamphlet which they have recently published on this subject, recommend that vessels of very large capacity should be employed-of 1,600 tons, for example, with engines of 246-horse power. Such a vessel, they say, would allow of 900 tons being appropriated to merchandise, 100 to provisions and water, and 460 to coals-which last would suffice, with occasional assistance from the wind, to carry her to the Cape, where a further supply of fuel could be obtained. The time occupied in the voyage is calculated not to exceed eleven weeks.

"I perceive," says Kinclaven, "that Mr. Cheverton declines giving a solution to the question (see No. 562). He kindly informs me, that it was a stale manoeuvre my proposing it.' Well, well; if the readers of the Mech. Mag. should think so, then let it be so. Still I believe that most of them will agree with me that Mr. Cheverton himself has been guilty of a much staler manœuvre, in trying to act the part of the fox in the fable, by contemning that which (he knows right well) is far beyond his reach.' There are also some most unfounded statements in his last postscript, which I shall reply to in due time. For a short period I leave him to the tender mercies of his new female opponent, the highly-gifted M. S."

A printed paper has been sent to us, entitled, "A General Description of Proposed Improvements in London, projected by Mr. W. D. Holmes, C. E." We do not approve of all the author's suggestions, but there are two of them which we think extremely well deserving of consideration. The first is, that the Regent's Canal should be drained and converted into a railway, in which case it would form an extension of the Birmingham line, to the Thames, through one of the busiest

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portions of the metropolis. The second is, d provide means for collecting, carrying rendering available, as manure, the filth which now runs from the common sewers into the Thames" (a thing often proposed before). Mr. Holmes estimates that" the amount of manure now passed into the river and otherwise wasted, exceeds 12,000 tons per diem;" and that it "may almost, without expense, be concentrated to about 7,000 tons, which will yield a profit of 400,000l. per annum, after paying all expenses attending it."

The Birmingham Musical Festival will take place, under the patronage of their Majesties, in the second week of October next. The spacious hall, in which the performances are to be held, is rapidly finishing; it will undoubtedly be one of the finest and best adapted rooms in Europe for the production of grand musical effects. The stupendous organ is also advancing towards completion. The hall, though of such dimensions as to be capable of holding nearly 8,000 persons, is so admirably constructed for the free transmission of sound, that it is believed the voice of a single speaker will be heard in any part of the vast area. -Cheltenham Chronicle.

Mr. Barton complains that Mr. Baddeley has misrepresented the actual construction of his metallic piston, in his communication of last week, respecting an alleged improvement of it by the Messrs. Heaton. He promises to send us, in time for insertion in our next Number, a paper in which this will be clearly demonstrated.

The contractors for executing the metropolitan end of the Birmingham railway, commenced operations on the morning of Wednesday last.

The completion of the beautiful new cut, by which the drainage of the Bedford Level has been rendered complete, and the Wisbeach river made navigable for vessels of 200 tons burthen, as far as the town of Wisbeach, was celebrated by a grand festival on the 23d ult. The plan was laid down by Mr. Rennie in 1824, and has been executed under the direction of Mr. Tycho Wing. It has cost about 200,000l.

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Communications received from Mr. MessiahMr. Bagster-Mr. Byrne-R.-P. G.

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. RICH, 12, Red Lion-square. Sold by G. G. BENNIS, 55, Rue Neuve, Saint Augustin, Paris.

M, SALMON, Printer, Fleet-street.

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