Danes, imitating the example of several others, have had the good sense very recently to adopt Merryweather's portable fire-escape ladders, which had only been stationed in the parish a few weeks when they were the blessed instruments, under divine Providence, of saving the lives of nearly a dozen individuals at a fire in the Strand on the 3d instant. One of the persons thus rescued, has addressed a letter to the Editor of the Morning Advertiser, expressing his gratitude for the promptitude and skill with which assistance was afforded, as well as his admiration of these ladders, which he acknowledges to be the very best means of guarding against the fatal calamities too often attending metropolitan fires.

Attention to this subject on the part of London parishes, is more needful than ever, since the failure and breaking up of that precious piece of humbug-the "Fire-escape Society.'

Many of our nobility have shown a laudable anxiety to counteract the destructive influence of fire, by suitable provisions for its suppression. The Dukes of Devonshire, Northumberland, Rutland, and Sutherland, Sir Robert Peel, with many other noble peers and wealthy commoners, have very respectable provisions for dealing with accidental or wilful conflagrations. But his grace, the duke of Buckingham, has surpassed all his compeers, in the extent and completeness of his fire-establishment at his magnificent seat, Stowe House, Bucks. His grace has already eight fire-engines; four of them are small portable engines, similar to those now so extensively adopted on board steam-boats, and shipping generally, a description of which may be found in your 645th number (page 226, vol. xxiv). These are stationed on different floors within the building, while four of a larger description are judiciously placed around the mansion. There are four elevated reservoirs of water within the building, furnished with connecting screws and leather hose, for direct application, or for supplying the portable engines. In addition to the above, Mr. Merryweather is now building for his grace a powerful carriage engine, with seven-inch barrels, precisely similar to those supplied by him to the London Fire Establishment, and furnished in the same complete manner. Twenty-four picked men from his Grace's domestics form his fire-brigade, six of them being armed and accoutred, in the London fashion, with axes and helmets. The whole is under the direction of an active and intelligent engineer from London. Due precaution has been taken to provide an

abundant supply of water, and Mr. Merryweather is building a travelling hose-reel, which will afford the means of rendering the most remote piece of water in the grounds, available in case of fire, in a very few minutes. So far as the protection of this splendid mansion is concerned, every thing is upon the most secure footing, though it is most devoutly to be wished that the provision thus made may never be required. The inhabitants of the country round for miles, will however participate according to their necessity, in the benefits of his Grace's protective measures, which, among other advantages, will be likely to counteract to a very considerable extent, the diabolical practice of incendiarism, which seems again to be on the increase in some of the agricultural districts.

To those who have the means of imitating the noble example of his grace of Buckingham, or indeed to every person to the extent of their ability, I would most earnestly say— "Go thou and do likewise." I am, dear Sir,

Yours very respectfully,
WM. BADDEley.

London, October 9, 1839.

Errata, in my last communication, page 20, col. 2, to line, "for two and three months"-read "two and three years."

NOTES AND NOTICES.

Photogenic Engraving.-The means have just been found of engraving the Daguerreotype drawings, and of engraving them on the spot. This very important discovery is due to Dr. Donné, who has had the felicitous idea of applying the ordinary process of engraving directly to the proofs taken with the Daguerreotype, However extraordinary this result looks at first sight, it is not the less certain and authentic. We have examined the first plates obtained by that able observer. They have been submitted to the Academy of Sciences, where they have caused a very great sensation. Dr. Donné's discovery appears to us almost as important as that of the Daguerreotype itself. When he shall have brought to perfection his engraving process, then only will the Daguerre apparatus prove to the traveller, antiquary, and naturalist, the most valuable resource. When the image of the most complex monument or most minute preparation of natural history shall have been finished, every traveller or observer, by immediately engraving the plate, will be able to compose himself the picturesque part of his work, and to multiply its proofs at a cheap rate. The primitive art which obliged us to make collections of unique pictures upon silver plates, is therefore about to take a far wider range. It will quit the cabinets of the curious, and enter the domain of the graphic arts in general and of popular education.--Paris paper.

Errata in the Review of Mr. Kentish's Treatise on a Case of Instruments. Page 22, line 7, for "plum rule," read "plain rule;" 1. 20, after "are," insert "not." P. 2, 1. 14, for "the little," read "this little;" 1.20, after "recommend," insert "it."

WING'S ROTATORY HYDRAULIC

ENGINE.

Sir,-When I was in the United States, in 1836, I went to Troy, up the Hudson River; near this city there is a dam across that river, the water from which drove some mill and machine-shop wheels. Amongst the wheels was Wing's patent re-acting wa'er-wheel; this wheel is on the principle of Barker's mill, but by far the best modification I have yet seen of that machine. It works horizontally, with a head of water over it of any height, so long as there is the slightest fall from it; the over and under-shot wheels being frozen up so many months of each year, first led to the invention. The following sketch will give some idea of its construction:

The same letters refer to similar parts in the different figures.

Fig. 1 is a plan of the horizontalwheel; A, axle; B, water-way to the segments, and the bottom plate; C, funnel or entrance for the water; D, cover over the segments, cast in one piece with them.

Fig. 2. A, axle: B, water-way and bottom-plate; D, segments with the cover taken off, and the funnel removed. The arrow denotes the direction the wheel revolves in.

Fig. 3. Side view. A, axle; C, funnel; D, segment mouths, or the exits for the water.

Fig. 4. The bottom-plate; it is bolted on to the other part of the wheel by the bolts F; G, open socket for the axle, which is fixed to the wheel by the screws seen in the socket; E, openings to prevent the pressure of the water upwards from being too great.

Fig. 5, is a section of the bottomplate, which is convex upwards.

The wheel is five feet in diameter, made of cast iron, cast in three pieces, viz., the segments, the funnel, and the bottom-plate; it is walled in, and no water allowed to pass, but what enters the funnel and rushes out at the segment mouths.

The sketches are not drawn to a scale.

Yours faithfully,

ARTHUR TREVELYAN,

Wallington, Oct. 9, 1839.

DESTRUCTIVE COMBINATION OF IRON AND LEAD.

Sir, It has often appeared to me extraordinary that in this scientific age, the use of one of the strangest errors in the combination of metals should still be persevered in, which must anciently have originated in ignorance of the effects, and seems to continue up to the present unnoticed.

Every one is aware, that when two metals come in contact, a galvanic action is produced; particularly if any thing in the shape of a sub acid intervenes. This is peculiarly exemplified in pewter, which gives considerable vivacity to porter, that is flattened by glass.

This action is strong or weak, and is more or less destructive to one of the metals, in proportion to the affinity for oxigen which is thus brought on it. If we are anxious to insure the preservation of all the metals that must, in many operations, be brought in contact with each other, we should take care to select such whose union creates this chemical influence as little as possible; although the very reverse of this has been hitherto practised, and has occasioned an unlimited expenditure, ninetenths of which might have been avoided.

There is not a square, and scarcely a house that is not surrounded with iron railings, and these are pretty universally fastened in at the lower extremity, by lead. This combination of iron and lead keeps up so strong a galvanic action through the medium of the oxigen of the air, that the rails are, in a very moderate time, eaten away at the junction entail an enormous loss that might easily of the two metals, which must yearly be prevented.

The iron, in this instance, becomes the protecting metal, and thus preserves the lead from decomposition, which never could have been originally contemplated.

Now, if instead of using the lead, which is thus thoughtlessly rendered an inveterate enemy to the rails, we were to substitute zinc, for instance, this galvanic influence would then become inrerted, the whole of its action would fall on the zinc, and the iron would be preserved, and as the zine is oxidated with difficulty, it would, at the same time, be scarcely acted on; the one remaining uninjured, and the other nearly so.

Paint, formed of the oxide of zinc, for the same reason, would preserve iron exposed to the atmosphere, infinitely better than the ordinary paint which is composed of the oxide of lead. In some instances of late years, iron covings have been used instead of stone. The rails are inserted in a square hole that just fits the bars, the unsightly method of filling up with lead is avoided, and all parts of the iron expand or contract equally in heat and cold. Whereas, with stone, the humidity in winter insinuates itself into the

51

cavities round the fittings, and as it fuzes and so increases in volume, it bursts the stone covings in all directions.

On some future occasion I will, with your permission, resume this subject, and show how this destructive chemical influence may be obviated in other arrangements, not less important to the interests of those concerned than the one here noticed.

Yours respectfully,

W. A. KENTISH.

This is a very neat and ingenious improvement upon the ordinary hinge. The hinge is divided into a number of socket joints, each socket or division having a stalk attached thereto, or forming one piece therewith, by which to fix it to the door or door-post,-lid or box, for which the joint is to be formed. The sockets, or divisions, are to be fixed (either by screwing them in, or putting them through holes and tightening with a nut,) alternately one in the door, and the next in the door post, and so on. Thus, suppose the stalks and sockets, a d, to be screwed into the door post,and the stalks and sockets, be, into the door, the pin, or pivot c, passes down

2.

through the four sockets, and thus forms the hinge joint. Care must of course be taken to place the divisions at accurate distances from each other, so as to make the holes in the different sockets coincide. Any length of hinge may thus be formed, by multiplying the number of divisions. For dressing cases, desks, and similar kinds of articles it is particularly applicable.

The specification describes various methods of fixing the sockets, and some modifications of the hinge to suit particular cases, but the foregoing explanation fully exemplifies Mr. Edwards's in

vention.

The broken lead ore is to be put in a wooden vessel lined with lead, then muriatic acid, of the strength of 1.10. is to be poured thereon. The vessel is closed air-tight-and the heat of steam applied until the whole of the ore has been reduced to the state of chloride of lead. The sulphuretted hydrogen evolved in this process, when sulphuret of lead is operated upon, is to be conveyed from the vessel by a pipe or other suitable means. The chloride of lead is then to be dissolved in hot water and lime, cream of lime or other earthy matter is to be thrown into the solution, by which the oxide of lead will be precipitated: about 60lbs. of unslaked lime are necessary to 100 lbs. of chloride of lead. By this process the sulphur of the ore is obtained in a state fit for use. Where the oxide is to be used as "blue lead," it must be submitted to the action of heat in a reverberatory furnace as with the oxide obtained by the usual process. Antimony is to be treated in a similar manner to that described of lead. chloride of antimony having been obtained, and dissolved in water, antimony itself will be precipitated; or if oxide is desired, about 60lbs. of unslaked lime is necessary to every 90 lbs. of chloride of antimony.

The

NOTES ON VARIOUS INVENTIONS-SMOKE CONSUMING-ILLUMINATING CLOCKSPLANISPHERES-ANCIENT FIRE-ENGINE.

Sir,-About four years back, Mr. Isaac Milburn, a mill-wright, in the employment of my father, accidentally discovered (the fact being new to him,) that steam entering a chimney prevented the issuing of smoke from its orifice; it was in the following manner in a small room is fixed an iron boiler in which flesh is boiled for dogs; the effluvia from the steam is very unpleasant, and to prevent it from issuing into the room, he carried a flat wooden flue close to the wall, from the side of the top of the boiler, into the chimney about 3 feet above its throat, after fixing this flue he went away about other business; having been absent an hour or two, he returned, and as he walked back cast his eyes to the chimney top, and seeing no smoke issuing from the orifice thought the fire had gone out-however, when he examined it, the fire was burning well, and continued without smoke as long as steam entered the chimney.

The ease with which modifications can be

made by any inventing mechanic of the methods of preventing smoke from issuing from the chimney or funnel orifice, by steam entering the furnace or flue, or by first cokeing the coal in the furnace, must render the numerous patents for those two methods of very little value; being old discoveries, any person can employ the principles without infringing any patent right.

In vol. xxxi, page 320, of your instructive Magazine, in the Notes and Notices, an account is given of a new contrivance to illuminate the face of the clock at the Horse Guards. When I was at Glasgow in the year 1826, the same method was employed to illuminate the face of the clock of the Tron church with carburetted hydrogen-gas, by reflection.

In vol. xxxi, page 70, a planisphere is mentioned as a new contrivance: I have had one for several years, the following is its title:"An horizontal sphere, showing the position of the heavens at any given time, manufactured by I. Addison and Co., globemakers to his Majesty George the Fourth, 50, London-street, Fitzroy-square, April 10th, 1824." It performs all the operations that your correspondent's does, and is made exactly similar to the description given by him.

In vol. xxx, page 87, is a description and wood cut of an ancient fire-engine, copied out of a work published in London, in 1590. A brother of mine lately returned from Rome, gave me a book which he bought there, of the following title and date:

"Theatrum Instrumentorum et Machinarum Jacobi Bessani Delphinatis, Mathematici ingeniosissimi : Cum Franc. Beroaldi Figurarum declaratione demonstrativa. Lugduni, apud Barth. Vincentium, cum Privilegio Regis, 1578."

In this book, amongst numerous excellent 'wood cuts of mechanical inventions, is a cut and description of the same fire-engine, but the working details are much clearer than the cut in your journal. The following is the title of the plate :

PLATE 52-"MACHINA MENTUM UT NON VULGARE SICUT OPINAMUR ITA SINGULARE IN EIA CULANDA AQUA ADVERSUS INCENDIA; MAXIME CUM FLAMMA SUPERANTE, NULLI PROPIUS AD AEDES PATET ADITUS.

Yours faithfully,

ARTHUR TREVELYAN.

Wallington, October 9, 1839.

ON CASE-HARDENING IRON.

Sir, I am particularly obliged to your correspondent "Iota" (page 479) for calling my attention to the article on case-hardening with prussiate of potass, which appeared in