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ent should have referred to ships of war as models for strength, which merchant builders would do well to imitate, it being notorious that ships of war, when taken into the merchant service, have always required additional strength to enable them to carry their cargoes with safety. Yet your correspondent recommends that the slight and inefficient scantling of men-of-war for mercantile purposes shall be substituted for-one which has proved to be better adapted to the purpose, but with the details of which he is evidently not acquainted.

The extraordinary cases quoted by him, even if true in all their details, are of vessels which were constructed with an unusual degree of strength for a particular purpose, but not more so than vessels of the same class are constructed for the merchant service in London. The "First of June" refers to the "Superb in proof of the inferiority of merchant steamers. Does he know the construc

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tion of the " Superb," her age, where built, and the precise circumstances under which she was lost? Unless he possesses full and correct information on these points, he is evidently incompetent to adjudicate in the case of the "Public versus Merchant Steamers."

The writer of this not long since saw one of the King's ships take the ground when quite empty, and in the course of a few days break off just above the floorheads, being too weak to sustain her own weight, notwithstanding she laid on a bed of soft mud. Are these the kind of ships, having 15 to 21 inches of solid timber, which the "First of June" recommends to be built for the merchant service, when they have occasionally to take the ground with their cargoes?

I might enter into an examination how far the plan of filling in solid conduces to the durability of the ship, but forbear, not feeling myself called upon to do so in the present case.

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I send you a copy of the Rules for the classification of ships in " Lloyd's Registry of British and Foreign Shipping,' in order that you may be able to judge whether the tendency of them is prevent safe vessels being built." Your integrity and candour will admit that, on the contrary, every inducement is held out to study strength of construction, with a proper regard to the selection of such materials as will be most likely to ensure the

durability and sea-worthiness of all ships which may hereafter be built for the merchant service.

I am, yours respectfully,

AN OLD CORRESPONDENT.

[We have looked over the Rules, a copy of which accompanied the preceding communication, and must frankly acknowledge that they have left on our minds a very different impression of their tendency from that conveyed by the letter of" First of June." But before offering any decisive opinion on the subject, we should like to see what that writer has to say in support of his charges. We find it difficult to persuade ourselves that any gentleman could denounce in such unmeasured terms as he has done the new Rules of Registration, without having much better grounds for his couduct than any which a perusal of the Rules themselves have suggested to us.-ED. M. M.]

WOODHOUSE'S SUBSTITUTE FOR CANAL

LOCKS ANTICIPATED BY FULTON.

Sir, It has frequently occurred that two individuals have, at distant times or places, hit upon the same expedient for accomplishing the same object. The plan described in No. 623, as a substitute for canal locks, is precisely similar to one given by the late Mr. Fulton in his thin quarto work on canal navigation. I was not aware that it had been in actual practice. In the same work, "Fulton on Canals," is a plan for transporting canalboats from one level to another, which he stated might also be applied for the purpose of facilitating the repairs of the boats used on the canal. The late Mr. Morton, of Leith, took out a patent for the three kingdoms for a slip of precisely the same kind for repairing vessels. I am inclined to believe that Mr. Morton never either saw or heard of Fulton's plan, and was, therefore, so far an original inventor.

Can any of your correspondents furnish a detailed account of a steam-raft recently fitted in the Surrey canal, which, from the description given me, is similar to that lately constructed in the United States ?

I am, Sir,
Your obedient servant,
GEORGE BAYLEY.

London, August 21, 1835.

THE NEW PAVING ON SNOW-HILL.

Sir, Your intelligent correspondent, Mr. Baddeley, has lately noticed a new mode of paving recently adopted on Snow-hill. The sketch that accompanies his communication is (either from the oversight of the draughtsman or engraver) not correct. As Holborn-hill is shortly to be paved in a similar manner, perhaps he will favour your readers with an amended representation and a particular account of the substratum, and the proportions of the grouting, if any, employed in bonding the work together. The plan recently adopted I consider to be good in principle, and, I may add, the best that has been hitherto tried for great acclivities. But certain destruction awaits the knees of any animal that may fall upon its ridged surface, till such time as the granite is reduced on its edges by the action of heavily laden waggons. At the same time I would suggest, that this plan should be adopted at the entrance of all branch streets and gateways that have an intervening gutter. The accidents that arise from the common practice of cross-paving at these particular points, are innumerable. Would it not be better to have the stones roughly rounded or prepared previous to laying? For I feel convinced, from careful observation, that a weight, equal to a waggon laden with coals, has a tendency to displace this paving considerably; besides, forcing large portions from the arris edge of the stones, thus rendering the improvement no better than that which has lately cost our worthy Corporation about 3001.

I am, Sir,
Respectfully yours,

C. DAVY, Architect.

3, Furnival's-inn, August 17, 1835.

RECENT AMERICAN PATENTS. (Selected from the Franklin Journal for May, June, and July last.)

IMPROVED SUCTION PUMP, Elijah Whiton, Massachusetts.-The barrels are to be made of steatite or soap stone; but the principal novelty is a contrivance for opening both the valves, and allowing the water to descend to prevent its freezing. There is to be a sort of spring catch on the upper surface of the valve of the lower box, which, when the pump handle is raised to the greatest possible height, hooks on to a ring, or other suitable appendage, on the lower end of the piston,

whilst, at the same time, a projecting pin opens the valve in the piston, or bucket, and the water necessarily descends into the well, or reservoir.

STRAW CUTTER, Stephen Ustick, Philadelphia. There is, we think, considerable novelty in certain parts of this machine, but it has the fault of too much complexity. The straw is to be contained in a trough, in the usual way, and is to be fed by fluted rollers of cast-iron. The knife stands horizontally, or nearly so, across a frame to which it is firmly attached. The lower edge of this frame rests upon ways, which form an inclined plane, and, consequently, as the frame slides, the knife descends with a drawing motion. To cause the frame to slide backwards and forwards, there is a pitman, worked by a crank, on the shaft of a flywheel in front of the machine.

PRESERVING TIMBER FROM DECAY, Forrest Shepherd, Fredericksburg.-The wood is first to be steamed, or boiled, to "destroy the sap, or principle of decay," and after this to be immersed in pyroligneous acid, until saturated. The patentee says that he also preserves wood from decay, and from destruction by worms, by boiling it in a solution of sulphate of iron, sulphate of alumine, and muriate of soda; or, in other words, in a solution of copperas, alum, and common salt, taking half an ounce of each to a gallon of water.

We apprehend that the foregoing direc tions are altogether empirical, and that the patentee has been guided more by his hopes than by his experience, which ought, in such a case, to be the result of long continued and varied observation. A patent was lately obtained for saturating timber with lime, which was to neutralize the acid supposed to be contained in it; in the present instance, it is to be made to imbibe as much acid as possible; these views are theoretical, or rather hypothetical, and must not be depended upon as guides. The present patentee's specification makes no claim, offers little or nothing that is new, and merely lays before us several recipes, from which to make a choice. The saline solutions named will do much towards rendering the wood incombustible, if they do not protect it against the attacks of the dry rot.

HORSE-SHOE-MAKING MACHINE, E. D. Rarre, and S. Field, Oakham.-In the lower part of a very stout frame of east-iron, a horizontal spindle is to run, in the manner of a lathe mandrel; one end of this spindle is to project through a collar, and to carry a kind of chuck, the face of which is to be grooved, so as to form a mould, into which the heated iron is to be forced in order to convert it into shoes. This moulding face is

to be about sixteen inches in diameter, and the groove about two inches clear of its edge. When horse-shoes are to be formed, the indentations for two of them are contained in the circle, two cutters, or chisels, being placed in it to divide the iron; for ox shoes, four such cutters are used.. There are to be creasing dies, corresponding with the number of shoes, on which are raised as many projections as there are nails to be employed. A punch, or punches, operated upon by cams, and passing through the moulder are to throw the shoes out of the groove.

In order to force the iron into the moulding-groove, there is a roller revolving vertically, the lower end of which roller projects through a collar, and bears against the face of the moulder. The heated bar is to be passed through an opening, or notch, which guides it between the roller and the groove, by which it is to receive its form.

We do not see in this machinery any thing calculated to remove the difficulties which have been hitherto encountered in the attempts to make horse-shoes by rolling. There has in every instance, we believe, been a considerable waste of metal, and fins have been left upon the edges, which not only increase the waste, but are difficult to remove; and, after all, the horse-shoe is not completed by the machine, but has to undergo considerable forging to prepare it for use. We predict, therefore, that it will prove a total failure.

FURNACE FOR HEATING BAR IRON, Henry Burden, Troy. - The patentee states that the common method of constructing furnaces for heating bar iron by anthracite (Welch coal), is to make them about three feet wide, and four or five long, with grates of these dimensions, and a door at one end for admitting the fuel, and the bars to be heated; the grates have on them a layer of three or four inches in thickness of ignited anthracite, upon which the bars are laid; but as flame from this fuel will not fill the space between the iron and the arch, and the heat is unequally distributed, the draft through the grate being more obstructed in one part than in another, the bars are frequently overheated, burnt, or melted, in spots.

To remedy this defect, the improved furnace is lengthened about one foot, and furnished with a door at each end; the anthracite is laid on the grate as usual, and when the bars are heated to such a degree as not to endanger their burning, the hinder door is opened, and a small portion of bituminous coal thrown into the back part of the furnace, which, flashing into flame, fills the furnace therewith as it passes over the iron

in its way to the chimney, and equalizes the "1st..

heat of the bars.

The improvements claimed are, Making the furnace with a door at the back end, so as to admit of the bituminous coal being put into the back part of the furnace. 2dly. Using the bituminous coal on a part of the grate at the back part of the furnace, reserved for that purpose, which gives the coal an opportunity of ignition, as well as could be by a reverberatory or puddling furnace, before it comes in contact with the iron. 3dly. In combining the use of anthracite and bituminous coal, for the purpose of heating bar, or other iron, at the same time igniting each in separate parts of the furnace."

From the nature of the thing, as set forth, and the known talents and experience of the patentee, we have no doubt whatever that the foregoing is a real and great improvement in the process to which it appertains.

ROTARY CYLINDER CANNON, John W. Cochran, Massachusetts.—It is believed by the inventor that "in actual service, either in attack or defence, the Rotary Cylinder Cannon will constitute a most formidable battery, being so constructed that discharges to almost any given or requisite number, and in rapid succession, and in a very limited period, may be made with accuracy, and with as unerring aim as with any other ordnance."

This

So far every thing is quite promising; but the value of promises, all will admit, is dependent upon the manner in which they are fulfilled, and, for our own part, we had rather be among those to be fired at, than in the company of the cannoneers, when this gun is discharged, as we should be much more in fear of the breech than of the ball. The barrel part of these guns is to be formed and mounted upon a carriage as usual, but the breech is to consist of a solid metallic cylinder, the periphery of which is to bear against the bore of the cannon, and to be capable of revolving upon gudgeons. cylinder is to be bored so as to form any desired number of chambers, which are to receive the charges, and these are to be brought round in succession, so as to coincide with the bore of the gun. The breech is to be made to revolve by an endless screw working in a toothed wheel, and there is a contrivance intended to deposit, upon nipple, percussion caps, which are to be exploded by a hammer. To render this gun the more formidable, it is represented in the drawing as double-barrelled, the two barrels to be discharged at the same time, two chambers being excavated in the cylinder, side by side.

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We think it very probable that the pa

tentee would never have needed a patent, excepting, perhaps, a patent coffin, had he, before seeking to obtain it, "made, constructed, and applied to use, his said invention or discovery." Our reasons for this opinion will not be required by those who have any knowledge upon the subject, and we cannot take time to prepare a horn-book for others. Even the firing of ordnance by percussion locks has been attended with diffi culties of no ordinary character, as is well known to many who have tried it.

GAS METRE, James Bogardus, New York. -The gas metre described in the specification attached to this patent, differs in its principle of action from all those which have preceded it, or, at all events, from those which have come to our knowledge. Its exterior form is that of an oval shade, such as are put over time-pieces, the longest diameter of which is about nine inches, its shortest six or seven, and its height fourteen. This exterior part is to be made of cast-iron, in two pieces, being divided by a vertical plane passing through its longer diameter, flanches being cast along its edges, to allow the two halves to be united by means of screws; this vessel has a bottom, so as to form a perfectly close box, and it stands upon short feet. On the front side of it there is an opening, formed in the casting, which is filled with glass, cemented in, air-tight, and affording a view of the index, and of the general operation of the machinery contained in the interior. In the lower part of this case there are two openings, one for the introduction of the gas from the reservoir, and another to allow of its exit to supply the burners.

We shall not attempt to describe specifi cally the construction of the interior, but merely to make known the general principles upon which the indications of this instrument depend. When the two shells are put together by their flanches, they are made to embrace a flexible diaphragm, of bladder, or air-tight cloth, which is loose, or bagging, in the interior, so that when gas is forced in on one side, the diaphragm will pass over to the other, and come into contact, or nearly so, with the shell. The induction and exit apertures above spoken of, are connected with pipes, which are cast on to the bottom, and are so constructed that they can communicate with either side of the diaphragm, there being a moveable cup, or cover, which is shifted at every vibration, thus producing an effect resembling that of the slide valve of a steam-engine. The diaphragm, of which we have spoken, is in part embraced between plates of sheet tin, leaving its edges and upper part free to obey the pressure of the gas admitted; this sheet tin works on pivots at the lower end, and can, consequently,

vibrate backward and forward with the diaphragm.

When the gas is admitted on one side, that on the other is forced out, by the action of the diaphragm upon it, and this, at the end of its vibration, reverses the communications between the induction and exit pipes, causing the gas to be admitted, and discharged, from the opposite sides. The same vibrating diaphragm acts also upon the wheel work by which the indices are moved, which point out the quantity of gas which has passed, by counting the vibrations, as one must necessarily be a measure of the other.

SCREW FOR PROPELLING CANAL BOATS, William Burk, Pennsylvania.-"The machine is on the principle of a screw, the worm, or thread, as it may be termed, being made to wind round a small shaft, one, two, three, or more times, as will best suit the motions of the machine. The size of the screw to be regulated by the size of the boat. The machine is intended to be applied to either end, or both ends, or both sides, or in the middle, of the boats intended to be propelled. This machine has an advantage over all others as to facility, and passing through the water with the least agitation." So says the patentee, but if we are to be guided by the result of experiment, repeatedly made, we shall be compelled to pronounce it to be one of the least efficient of all the plans tried. Who was the first inventor, we have not sought to learn, but there is a full description of the same thing in the "Annals of Philosophy" for 1818, vol. xi. p. 138.

Were our canals and rivers filled with some semi-fluid, having a good portion of tenacity, these screw propellers might travel onward without scattering or communicating a rotary motion to it, as they do to water, whilst the boats to which they have been attached. have advanced with no more than a snail-like speed.

CIRCULAR TENTER BARS, Stephen R. Parkhurst, Rhode Island.-The whole title of this patent is for "the tentering and drying all kinds of woollen and cotton goods;" and the contrivance appears to be a very good one, performing, in a small space, what, by the ordinary method, occupies considerable room. The apparatus consists of two wheels upon a shaft, which must be of such length as will allow the wheels to stand at such distance apart as shall be equal to the width of the cloth to be tentered; by means of a screw, the distance of these wheels may be easily regulated. Upon the inner surface of each wheel, a spiral of wood or metal runs from the shaft to the periphery of the wheel, the threads of the spiral to be about four and a half inches apart. Holes are bored through these spirals, at the distance of from two to

NOTES AND NOTICES.

four and a half inches apart, and through these holes there pass iron pins, which slide and turn freely in them, and have heads formed on the outer, and hooks on the inner, side of the wheel. The shaft and wheels are supported on a suitable frame; one end of the cloth is attached by hooks near and parallel to the shaft, and the edges to the spirally-placed tenter-hooks; after which the cloth is to be properly strained in width, by means of a screw nut, which removes the wheels farther apart. The diameter of the wheels will be governed by the length of the cloth to be received on them.

The advantages of the machine are, that it may be used in a small room-it renders the cloths even for rolling up-keeps the nap perfectly smooth, and expedites the drying.

COOKING BY GAS.

Sir, In the Mechanics' Magazine of 4th July last, I notice a quotation from a New York paper on the subject of cooking by gas. The letter from which that quotation was extracted, was addressed by me to Lambert Suydam, Esq., President of the Manhattan Gas Company, New York. I beg, through your publication, to confirm all the statements there made, except that of the probable number of families now using gas for cooking in England, which has certainly not come up to my expectations; but such is the present demand for apparatus, that by another summer, I have no doubt, thousands will be in use.

In my own house we light no fire but gas, nor shall do even in winter, for cooking. Our servants are delighted with it, and can manage it well. With the expense of twenty to thirty cubic feet of gas, at 10s. per thousand feet, we have dressed a dinner, consist ing of roast, baked, hashed, and boiled, sufficient for a party of twelve persons; and for an expense of two feet of gas per hour, we can have boiling water all day and steam for cooking, if required. My apparatus has cost me about 57., but is rather large, as my family consists of eleven persons, servants included.

Your humble servant,

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conducting for the last three days, in presence of a deputation of the directors of the principal railway companies, and particularly of the London and Birmingham Railway, a series of very interesting experiments on the rails, chairs, sleepers, &c, and the mode of attaching them. The Swiftsure locomotive-engine, made by Messrs. George Forrester and Co., of the Vauxhall-road Foundry, in this town, attended the scientific party.-Liverpool Advertiser.

The Comet.-A correspondent of the Dublin Evening Mail, who signs himself "Charles Cameron," of Dungarvan, says he distinctly saw the comet with his naked eye, on the morning of the 17th instan, which was at least one month before the time astronomers have fixed for its being seen by the unassisted vision of any other person. The Irish star-gazer seems to have had a much better view of the heavenly body than our astronomers with their best telescopes, for whilst they speak of it as a scarcely perceptible nebuloid, he says he could distinctly see its oblong form, and that it appeared much brighter than Sirius on the clearest night. Another Irishman boasts of having seen two One may guess what produced this second

comets.

sight.

London and Greenwich Railway.-The works of this undertaking, which Mr M'Intosh has con-. tracted to complete, are now proceeding with the utmost activity; an average number of between five and six hundred men being employed daily; and the purchase of the remainder of the property through which the railway will pass, is proceeding in a most satisfactory manner, affording the most pleasing anticipation of a speedy commencement of the running of the carriages now collecting at the depot at Deptford. The works already extend from Deptford to the Neckinger-road, and, again, from London Bridge to Bermondsey-street, leaving only the distance of about 1,200 yards to join and complete the main works from London Bridge to Deptford; and the value being fixed for a great part of the property not pulled down, it only remains for the legal forms of transfers to be executed, to put the Company in possession of the whole of the ground to that extent. It will be satisfactory to the shareholders to learn, that from an examination of the cost of the works, of which so large a por tion is now erected, and the purchases effected of so much of the property, it is the opinion of the engineer and surveyors, that the original estimates will not be exceeded; and that the value of property possessed by the Company which they will have to re-sell, will, it is calculated, realize full, if not more than one-fourth of the whole purchase money.

H. F.-Messrs. Barclay and Sons, Farringdon

street.

Communications received from Mr. Davy-Colonel Macerone-T. C.-Mr. Coggan-Mr. Dines.

Patents taken out with economy and despatch; Specifications prepared or revised; Caveats entered; and generally every Branch of Patent Business promptly transacted. Drawings of Machinery also executed by skilful assistants, on the shortest notice.

LONDON: Published by J. CUNNINGHAM, 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. CUNNINGHAM and SALMON, Printers, Fleet-street.

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