come a great resistance, the shock against the atmosphere is more sudden, and the report louder." Although these two accounts appear contradictory, they are nevertheless both true. Facilitating and resisting the exit of the charge, do both increase the loudness of the report; a satisfactory explanation of this seeming paradox is required.

Several of the cases which I submitted as tending to invalidate the old theory of sound, A. Z. has not noticed; of the explosion of the mixed gases he has taken an unfair view.

I stated that a loud report ensued when the mixed gases were fired in a close vessel. A. Z. explains this phenomena with the aid of two open vessels: perhaps he will be kind enough to reconsider the question within the prescribed limits.

G. L. S. p. 46, has rushed into the field of controversy, without exactly understanding the position of the combatants; he expresses his surprise that I should have adopted an idea, which it was the sole object of my communication to dispute. I may be permitted to express my surprise, that G. L. S. should have been guilty of such an oversight. However, we appear to be pretty well both on the same side of the question, with the exception of a few minor points, on which I will join issue hereafter; and, as he has cut out plenty of work for A. Z. for the present, I shall not at this time go any deeper into the question.

In the mean time I solicit the attention of your numerous readers to the question of the correctness of the OLD LIGHT theory of sound-or the propriety of introducing a more satisfactory one, under the auspices of the NEW LIGHT.

to Euclid. Whether those solutions are or are not correct, your mathematical readers will have very little difficulty in determining; they set up no claim to excellence; the writer's sole object was, to meet, with a plain answer, the request of an "unaided mechanic," apparently disregarded by every one else.

K. assigns three reasons for preferring his solution of the first question to the other solutions. To his first, reply, that in my solutions of the propositions in Newton's Appendix to Euclid's Elements, and data, I had remarked, that instead of directing that AD be made=AB, we might apply 23. I, in making the angle ACD DAC; but the former was preferred as being more easy in practice. Hence, likewise, my solution is susceptible of the application of 23. I. In answer to his second reason,' "I ask, whether there is indeed any advantage, under the circumstances of the problem, in his construction, being applicable to "the more general problem" he has specified? With the property demonstrated in 32 of Book I. of the Elements, a more general" simple problem than his said “ one, has never been proposed for a schoolboy's exercise; and without this property, he cannot solve even what he designates "the particular case.' This general problem is, in fact, a very easy and direct application of 23. I. As regards my solution, it is sufficient to observe, that all which was required, as far as practicable, was effected, and that, too, I had almost said, in the simplest and neatest form;* but I wish to avoid invidious comparisons-the thing is before your readers, and they can judge. I will merely add, that viewing the question as a particular case of a general problem, to have proceeded scientifically, the particular solution should have been deduced from the general one, and not vice versa. To his third reason," I have only to reply, that it certainly must be matter of regret to young mathematicians, that K. forgot to specify a few of the numerous applicatious of his comprehensive con

struction.

BUSTON'S FIRE-ESCAPE.

Sir, It was with much pleasure, that I read in your last Number an account of another successful trial of the fireescape invented by the late Mr. Samuel Buston; showing, that although there has not been any loss of life by fire lately, the subject of the best mode of escape in the event of such an occurrence, is not quite forgotten.

One important advantage attending the exhibition of this escape, is, that it serves to show publicly the safety and efficacy of this mode of descent. But the great practical lesson to be derived from these experiments, and which cannot be too often or too strongly enforced upon the attention of firemen, policemen, and others, is, that in every place where a sheet, blanket, or carpet, &c., can be procured, assistance may in this way always be offered to the inmates of a burning dwelling.

I would strongly recommend a repetition of the experiments with this fireescape at every police-station in the metropolis; carefully explaining to the men at the time, the numerous articles which may be made subservient to the purpose, when a regular fire-escape of this kind is not at hand.

FIRE-PROOF FLOORS.†

There is a particular description of floor, which, although not altogether fire-proof, is certainly (at least, so far as I can judge) almost practically so. It is composed simply of plank 2 or 3 inches thick, so closely joined, and so nicely fitted to the walls, as to be completely air-tight.

Its thickness, and its property of heing air-tight, will be easily observed to be its only causes of safety. Although the apartment be on fire, yet the time required to burn through the floor, above or below, will be so great, that the property may be removed from the other floors, or, more probably, if the means of extinguishing fire is at band,

* See vol. ix. pages 213 and 310, and vol. xi. p. 82.

From Mr. James Braidwood's work, on the Construction and Management of Fire-engines, &c.

79

it may be subdued before it can spread to any other apartment.

The doors must, of course, be made in proportion, and the partitions of brick or stone.

ON DEAD LIME.

Sir,-In certain circumstances, carbonate of lime is changed by burning into lime, which does not heat with water, nor slake, and which is called dead lime.

There are four cases in which dead lime may be formed :

1. When the limestone contains much alumine, and it has been heated so as to harden the mass.

2. When the limestone contains silica, and it has been strongly heated after the expulsion of the carbonic acid.

3. When the limestone is so strongly heated as to be in some measure melted, in which case the carbonic acid is fre

quently not entirely separated from the central parts of the large lumps, and they of course effervesce with acids.

4. When the limestone is strongly heated after the total separation of the carbonic acid, so that the lime neither splits when water is added to it, nor does it effervesce with acids.

Dead lime has been formed from chalk or oyster shells; but the circumstances from which it originated have not, I believe, been ever discovered.

It grows very hot with dilute muriatic acid, without omitting any carbonic acid gas. It remained 24 hours in water without slaking, but formed lime-water; when calcined oyster-shells were put into a boiling ley of soda, they were completely decomposed, and formed a very fine cream.

If you think these observations worthy of notice, they are at your service, and your inserting them will oblige,

Yours, &c. H. B. ANDRews. Oct, 23, 1831.

INQUIRY.

Silver-work. What is the method by which the dead-white appearance is put on silver (usually, I believe, called frosting) which we see on silver neck chains and ornaments? I have been informed it is done with vitriol, but am at a loss to know how it is used:-An Old Subscriber at Oxford.

LIST OF NEW PATENTS GRANTED, FROM THE 20TH OF SEPTEMBER TO THE 20TH OF OCTOBER, 1831.

Andrew Ure, of Finsbury-square, M.D. for an improved apparatus for evaporating syrups and saccharine juices. Six months, to specify from September 22, 1831.

William Bingham, of Saint Mary Hall, Esq., and William Dupe, gunmaker, both of Oxford, for certain improvements on fire-arms of different decsriptions. Six months, September 24, 1831.

Henry Hope Werninck, of North-terrace, Camberwell, gentleman, for certain improvements (coinmunicated to him by a foreigner residing abroad) in apparatus or methods for preserving lives of persons and property when in danger by shipwreck, by speedily converting boats or small vessels of ordinary description into life-boats, and other apparatus or means applicable to the same objects. Six months, September 24, 1831.

James Lang, of Greenock, flax-dresser, for certain improvements in machinery for spreading, drawing, roving, or spinning flax, hemp, and other fibrous substances, dressed or undressed. Two months, September 24, 1831.

Joseph Gillott, of Birmingham, penmaker, for an improvement in the making or manufacturing of metallic pens. Two months, September 27, 1831.

John Myatt, of Tabernacle-walk, Finsbury-square, tailor, for an article to be worn on the feet as a substitute for pattens or clogs, which he denominates Myatt's Health-Preserver. Two months, September 27, 1831.

Oliver St. George, of Great Cumberland-street, Middlesex, Esq., for certain improvements (communicated to him by a foreigner residing abroad) in machinery for acquiring power in tides or currents. Six months, September 28, 1831.

Miles Berry, of the Office for Patents, 66, Chancery-lane, engineer and mechanical draftsman, for certain improvements (communicated to him by M. Jean Nicholas, Senéchal Ingenieur des Ponts et Chaussees, residing at Versailles, in the kingdom of France) in the boilers or generators of steam and other vapour, and in engines to be worked by steam or vapour for propelling or actuating machinery on Jand, and boats, vessels, or other floating bodies, on water; and also in the mode of condensing such steam or vapour. Six months, September 28, 1831.

John Heathcoat, of Tiverton, Devon, lace-manufacturer, for improvements in the machinery used for the making of bobbin or twist lace net, whereby net and other fabrics may be produced. Six months, October 3, 1831.

Samuel Crosley, of Cottage-lane, City-road, Middlesex, gas-meter manufacturer, for an improved gas-meter. Six months, October 3, 1831.

Daniel Dunscomb, Bradford, a citizen of the United States of North America, but now residing in Dorset-place, Mary-le-bone, for an invention of certain improvements in lainps (communicated to him by Solomon Andrews, residing at Amboy, New Jersey, U. S.) Six months, October 4, 1831.

Peter Young, of Fenchurch street, London, rope and sail maker, for a new mode of manufacturing mangel-wurzel, for the purpose of producing various known articles of commerce, communicated to him by a certain foreigner residing abroad. Six months, October 6, 1831.

John Christopher, of New Bond-street, London merchant, for an improvement in clothes' buttons. Six months, October 7, 1831.

William Drake, of Bedminster, near the city of Bristol, tanner, for an improvement or improvements in tanning hides and skins. Six months, October 7, 1831.

George Lowe, of Brick-lane, Old-street, Middle sex, civil engineer, for an improvement or im provements in and connected with the manufacture of gas for illumination. Six months, October 12th, 1831.

William Hale, of Colchester, machinist, for improvements in machinery or apparatus for propelling vessels, which improvements are also applicable for raising or forcing fluids. Six months, October 13, 1831.

William Ainsworth Jump, of Marston, Chester gentleman, for certain improvements in drawing or extracting salt from salt-pans. Six months, October. 14th, 1831.

John Cowderoy, of Britannia-street, Hoxton Middlesex, gentleman, for certain improvements iu machinery or apparatus to be used in the process of making or manufacturing bread and biscuits. Six months, October 14th, 1831.

John Smith and William Dolier, Liverpool, gentlemen, for, a durable copy-book or writingtablet, and improved delible ink to be used therewith. Six months, October 14, 1831.

Thomas Henry Pollard, of Park-street, Grosvenorsquare. estate and house agent, for certain improvements in chimneys by the application of a mechanical apparatus as a smoke conductor. Two months, October 19, 1831.

.

Mr. Henderson.-The house in town say they have no regular communication with that in the country, and we cannot find any other that has.

A letter was left for F. H. last week, but omitted to be given to him by the Publisher when he called.

H. B. A. The papers received will be inserted. The one promised will also be acceptable.

Communications received from Mr. RontreeMr. Beare-Mr. Saddington-S. Y.-A MechanicT. M. B.-A Tea Dealer-A. F. T.

-r.

Errata.-P. 56, for A. at the uppermost wheel in the engraving, read B.

P. 57, col. 2. 1. 16 from the bottom, for "level" read bevel."

LONDON: Published by M. SALMON, at the Mechanics' Magazine Office. Wine-Office-court, (between 145 and 146) Fleet Street, where Communications (post paid) are requested to be addressed. Sold by G. G. BENNIS, 55, Rue Neuve, St. Augustin, Paris.

M. SALMON, Printer, Fleet Street.

PLANS FOR APPLYING BRAMAH'S PRESS

TO CYDER MAKING.

No. 1.

Sir,-Your correspondent at Stiverton, will, perhaps, find that the accompanying sketch will solve his query about ap plying the power of Bramah's press to cyder making, and in such a manner that the pressure shall be above the cake (No. 428, p. 63).

A (fig. 1, preceding page) is the head of the apparatus; BB the sides; E a platform; F cylinder; G a pipe to convey water from the pump; D a circular grooved box; C a fixed plug; H a pipe to carry off the juice.

If the cake is put into the cylindrical box D, which is just large enough to receive the fixed plug C it will rise when water is pumped into the cylinder and receive pressure from C, on the upper side. He may take his cake out by a moveable bottom to the box with attachment to fit into the square grooves, something like the instrument his wife uses to remove her mackarel after boiling, (without breaking them). The small greoves will allow the juice to descend to the bottom, and run out of the pipe H in front of the box.

scription of a steam-boat paddle-wheel which I lately invented, and which is applicable in a high degree to twin-boats which ply on canals and rivers. It has little or no tendency to break or agitate the water, or to endanger the embankments the water having scarcely any lateral surge, its flowings following the direction of the boat. This important result is obtained by means of moveable float-boards, which, when entering the water take hold of it, and thereby cause it to be propelled smoothly from between the boats, while, on leaving the water, they rise therefrom, with an inclination. The mode of action will be readily understood from an inspection of the accompanying figures, which exhibit a side view and section of a wheel with those paddles (figs. 4 and 5, front page).

A is the centre of a cast-iron wheel, of twelve arms, each of which has a longitudinal slot (or mortice) to receive the ends of the cross bars, a; in the section, these have a rectilineal motion from their connection with the excentric ring B afterwards described. These bars are pivoted from the arm of the wheel outward, upon which parts the connectingrods D, and pulleys C are fixed. B is the centre of a cast-iron ring or excentric (being a fixture) formed with a groove in each of its sides internally, in which the pulleys C revolve, taking with them the bars a, and connecting-rods D. These rods communicating with the iron band or hinge F (to which the floatboards are attached) by a joint at E, gives to the float-boards a progressive, and at other times a retrograde movement. The hinge F, it must be observed, is moveable on a joint at the armend G; this is fully shown by the side view, in which the circular dotted double line represents the excentric ring, and the horizontal dotted line, the height the water is supposed to rise on the wheel.

We will now suppose the wheel to commence a revolution, and in doing so, we will conceive the float described to take the place of that seen entering the water on the right. The common_motion of the wheel being from right to left, will cause the float at that part of the circle, to exhibit the appearance as shown in the side view; in this case it takes hold of the water with little tendency to agitate it, and from its pre