bows of the ship when there is uniform motion. Hence the work done on the propeller is greater than the work done by the resistance on the bows, by the product of that resistance, and the excess of the velocity of the propeller above that of the ship. This is so simple an argument that it does not need the assistance of mathematical notation to make it intelligible. "Y" may verify this for himself by making an experiment with a boat-hook and oar, observing how much more effectively he can set a boat in motion when shoving off with the former than when rowing with the latter.

To the fourth paragraph of the letter, I answer that I make no 66 supposition," " and that the deduction made is a reasonable one and involves nothing to justify the note of admiration with which it concludes, as it is a mere common-place.

The fifth paragraph too is quite true; I should not have hesitated to adopt it myself if I could have seen what it has to do with the matter. If "Y" imagines me to have

said that "the propeller " is not "the agent through which the power of the engine is made available for propulsion;" that "the velocity V or (v + v) of the propelling area, and the work done by the engine," are not "regulated by the resistance to be overcome at a given speed of the ship," he has much misapprehended me. The last paragraph hardly requires any answer. I will say, however, that "ascertained facts," so far as I am acquainted with them, "bear out the assertion that a loss of power arises from the obliquity of the blades:" and no facts can prove what "Y" says they do. They would prove the contrary.

It is my conviction the estimate I formerly gave of the advantage of the direct over the oblique propeller is below the truth. Let it be understood that, when these are compared, the only distinction between them should be the inclination. A direct propeller, acting at a foot from the surface, must not be put in competition with an oblique one acting at a depth of fifteen or twenty feet.

I am, Sir, yours, &c.,

A MECHANIC.

ON BOILER EXPLOSIONS. To the Editor of the Mechanics' Magazine.

REPEATED reports of the explosions of boilers lead us to ask how long the lives of those who have to labour or reside near to them are to be placed in jeopardy by the carelessness of those whose place it is to attend them. As soon as the excitement of the moment is gone, we are again lulled into

security. It is quite time, however, that the public, and especially the operatives connected with the various manufactories in which boilers are used, should be able to repose more confidence upon the attendants, and until the great amount of ignorance that prevails among that particular class is removed, there will be no safety. Such persons seem to be totally incapable of any other idea than that which is necessary to the mere feeding of coals to the fire; and the masters, in some places, have little or no more knowledge of a subject about which they ought to be so much concerned. To devise a remedy for the evil, would be a very difficult matter; however, in the first place, all the attendants (or firemen and engine. tenders) should undergo some kind of an examination, by qualified men, before their appointment is made. This is done in the naval steamers, and it is attended with good results. They ought to possess some me. chanical knowledge, such as calculating the power of the lever, by which they would be enabled to judge of the danger they run, by placing different kinds of weights upon such lever. There have been various explanations given, from time to time, of the causes of boiler explosions; but these, when they are compared with each other, are often conflicting and contradictory. One person will come to the conclusion that when the water gets too hot, and the plate to nearly a red heat, that gas is instantaneously formed, and caused to explode with great force; while, on the other hand, another party will argue that the pressure of the steam increases so much in a very short space of time, that unless the safety-valves are loaded carefully to the pressure the boiler will sustain, and are made large, and well attended to, an explosion must be the consequence. With the latter view of the question I am inclined to coincide. There have, as I have before mentioned, been several mechanical remedies proposed; such as when the water gets too low, an apparatus may be brought into action to admit steam into the furnace to put out the fire, or reduce its action. There are also various forms of signal-whistles for the same purpose; some are found to be very useful, but others, again, are rendered useless by the stupidity or absence of the attendants. It sometimes happens that the best-formed safety-valve may be stopped in its action through neglect, as when sticking to the seat, &c., occurs: to avoid this, I would propose that the valves be made spherical, and rest upon a narrow seat, and that the weight be suspended by a rod in the interior of the boiler, the rod and weight being so encased that the attendant cannot interfere with it. At the bottom of the rod there

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furnace, fitted according to Mr. Manley's arrangement, at the works of Messrs. Cubitt and Co., Gray's Inn-road. A is the old, and B, the new door of the furnace, the former being now blocked up; C is the cistern which supplies the water to the vertical shaft, D, which leads from the flue, I'I', down to the water-tank, F. I is the old flue, which formerly led (as shewn) from it into the vertical portion of I' I', which being continued upwards formed the chimney; this is now, however, quite cut off. The operation of the furnace is as follows:-When a fresh charge of fuel is thrown in through the door, B, smoke is produced, and traversing the flue, I' I', enters the vertical shaft. D, down which it is carried by the action of the water which streams from the cistern, C, through The denser a pipe terminating with a rose. portions of the smoke are thus precipitated into the water in the tank, F, from which they pass into a sewer, while the lighter rise and are received into the pipe, F, which conducts them back to the entrance of the furnace. The action of the water is rendered more effective by the projections, a a, which compel the gases to travel in a circuitous path.

The working of the furnace is represented as highly satisfactory by the persons in charge of it, and steps, we believe, are being taken for avoiding waste, by securing the lamp-black which at present passes away into the sewer, and which is of a superior quality. The application of the arrangement has effected a great reduction in the quantity of fuel required for the furnace, in which a much more equable temperature is sustained than could before be kept up.

largest iron-foundries in Birmingham, and the result, we are informed, has been, that the liquid purifier, which is used without the smallest danger, is proved to be capable of imparting to the metal superior strength and toughness. At this foundry the liquid has been introduced at least twenty times into the ladle whilst the iron was running from the cupola. Several bars were made in this way and others in the ordinary way, both of the same size and metal; on being tested for strength, it was found that the purified Some iron was fully 16 per cent. stronger, pig-iron prepared in the same way was afterwards put back in the cupola, and on being re-melted, and cast again into pig, it was found to be further improved. In the cupola the liquid was introduced four times, and was always found to act powerfully upon the metal, which it purifies in the cupola; and when the metal was run into the ladle, there was little to skim from the top. "The fireman asserts," says the Mining Journal, "that he clears out the cupola in half the usual time, and with little labour, and that the moulders generally notice the next day that the first three or four shanks of metal drawn mostly partake of the properties of the previous day's operation. Whether introduced into the ladle or into the cupola, the castings made with the liquid are always cleaner, better, and stronger. The price that Mr. Phillips has fixed for this useful preparation cannot fail to render the adop tion of it a source of economy 10 the trade generally. To the public, also, it will prove very beneficial, by producing good sound castings instead of the many defective ones which the manufacturer is compelled to send out, in consequence of the very bad pig-iron which is now produced from many of the blast furnaces, and in which from 20 to 30 per cent. of cinder and other dross and rubbish is frequently found. We understand it is Mr. Phillips's intention to introduce this liquid into the puddling and blast furnaces, and from what has been shown of the effects in the cupola, where only a small quantity of liquid was introduced, there is little doubt of its success. On behalf of the iron trade generally, we call on all the respectable ironmasters to give it a fair trial, which we have Mr. Phillips's authority to state would be done on his part gratuitously, as have been all the experiments he has hitherto made." The originator of the method has received numerous communications from ironfound.

ers and others in various parts of the kingdom, to all of which we have reason to know he has replied satisfactorily, giving reference to the firms where the experiments above referred to were instituted.

It must not, however, be supposed that the liquid purifier is applicable to the manufacture of iron only, as it has already been applied to that of copper and brass also, and has been found in these cases to bring up to the surface of the metal in the erucible or melting-pot (either in or out of the furnace) all the dross and impurities almost immediately, in consequence of which the eastings formed are stronger, tougher, and more compact, and consequently better adapted to boring and turning than when the ordinary mode of fluxing is adopted. It is scarcely necessary for us to say that the influences which will be exerted by such an improvement as this, should it become fully established, will extend to every branch of our manufactures.

We are pleased to find that Mr. Phillips has been very cordially welcomed by many of the Birmingham firms as a benefactor to the trade, and to the public also. He has had, of course, to encounter many prejudices, but the advantages derivable from the purifier are becoming rapidly appreciated. Among other establishments where the indefatigable discoverer has been, may be noticed the paper mills belonging to the highest civic authority of the borough of Birmingham, who received him with great kindness, and having listened attentively to his statement of the effects on metals of the mixture, and of what he proposed doing at the paper-mills, the worthy mayor at once went thither with him, and whilst the machine was in operation, Mr. Phillips introduced a small quantity of the liquid; in about a minute, we are informed, a piece of paper was produced of decidedly different texture to the bulk then making. This is not, of course, to be considered as a fair test or experiment, but merely as showing the extraordinary power of the liquid purifier, whether applied to hard or soft substances. Instances of its effect on other articles might be related, but enough is here shown to prove that various sources of our national prosperity are likely to derive advantage from its introduction into the factories at Manchester and elsewhere, to which, we understand, Mr. Phillips proposes to turn his attention as soon as he has firmly fixed the application of it in the metal trade.

We will conclude this notice by stating that we shall shortly revert to the subject, which must be one of much interest to our readers. Before we close, however, we think it right that we should call the attention of

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those who are charged with the erection of the new iron bridge at Westminster to this invention, and suggest the propriety of their testing its merits, with a view, should it be found valuable, to its adoption in the manufacture of the iron to be employed in that structure; Mr. Phillips having assured us that he is ready to supply the liquid at a small charge per ton.

SPECIFICATIONS OF PATENTS
RECENTLY FILED.

COLLETTE, CHARLES HASTINGS, of Lincoln's-inn-fields, Middlesex, gentleman. An improved method of reducing ores. (A communication.) Patent dated February 3, 1854. (No. 269.)

The patentee having placed the ore, together with coke, in a retort, the latter is then heated to redness, and the reducing gas or gases, such as hydrogen, carbonic oxide, or carburetted hydrogen, having been prepared, are introduced into the retort, and made to traverse the contents, the gaseous products being allowed to pass off.

NEWHOUSE, ROBERT BROCKMAN, of Uckfield, Sussex, surgeon. Improved apparatus for conducting off the gases of combustion from open fire-places. Patent dated February 3, 1854. (No. 270.)

The inventor provides a casing composed of plate-iron, or other suitable material, and of a length sufficient to project into the mouth of the chimney when set vertically above the grate. This casing at bottom exceeds in width the grate to which it is to be applied, and it gradually contracts both in width and depth towards its upper end.

LONGMAID, WILLIAM, and JOHN LONGMAID, both of Beaumont-square, Middlesex. Improvements in the manufacture of vegetable charcoal. Patent dated February 3, 1854. (No. 273.)

This invention consists in employing wood sawdust, or other vegetable matter in a state of dust or subdivision, and in acting on the same with sulphuric acid and water. The liquid is then filtered off and the charred dust dried, and, if necessary, ground to a fine powder.

HOWARD, EDWARD, and DAVID PORTER DAVIS, of Massachusetts, United States. Improvements in machinery for sewing cloth or other material. (A communication.) Patent dated February 3, 1854. (No. 274.)

The inventor describes a method of forming the needle tubular, and placing the closing-slide within it, and of constructing a groove or thread-passage, the object of which is to support the thread and prevent it from "kinking or injurious springing,"

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MEEUS, PIERRE JOSEPH, of Paris, France, engineer. Improvements in the manufacture of threads from or with gutta percha, and in ornamenting the same. Patent dated February 3, 1854. (No. 275.)

Claims-1. The manufacture of gutta percha threads by cutting thin sheets of gutta percha into strips, and twisting such strips either singly, or two or more together, with the aid of heat and compression, so as to form round threads. 2. The manufacture of gutta percha threads by twisting or twining a strip or strips of gutta percha round a thread or core of textile material or metal, or by passing such thread or core through a solution of gutta percha. 3. The ornamenting of gutta percha threads by the direct application thereto of metal, leaf metal powder, or other substance in powder either before or after such threads have been woven or otherwise worked into fabrics.

MILLS, GEORGE, of Glasgow, Lanark, Scotland, gentleman. Improvements in the construction of steam vessels, and in steering the same. Patent dated February 4, 1854. (No. 277.)

Claims.-1. The construction of twin vessels of suitable form, with straight inner sides, and their combination in such manner as to constitute one vessel, with a water way through its centre. 2. The adaptation and application to such vessels of thwartship paddle-wheels for steering or manœuvring them.

NEWTON, ALFRED VINCENT, of Chancery-lane, Middlesex, mechanical draughtsman. Improvements in springs applicable to railway carriages and other uses. (A communication.) Patent dated February 4, 1854. (No. 278.)

This invention "consists in sustaining the outer coil of a flat volute spring by a case, when this is combined with the application of the force in lines parallel or nearly so with the axis of the coil of the spring, by connecting the outer coil of the spring with one, and the inner coil with the other, of the two bodies to be kept apart with a required elastic medium."

BOYDELL, JAMES, of Anchor Iron Works, Smethwick, near Birmingham. An improvement in the beds of reverberatory furnaces used for puddling iron. Patent dated February 4, 1854. (No. 279.)

Claim. The application of the refuse products of iron obtained in burning pyrites (for the manufacture of sulphuric acid and sulphur), in the making of the beds of reverberatory furnaces used for puddling

iron.

LITTLE, WILLIAM, of the Strand. Improvements in distilling or obtaining products from coals and bituminous substances. Fatent dated February 4, 1854. (No. 280.)

In carrying out this invention, the coals or bituminous substances are placed in a vessel, which is connected to a fire-place by a flue or passage, and also with a suitable condensing apparatus by another passage. Air is decomposed by passing through a red fire, and the products, alone or combined with steam, pass into the vessel and act upon the coals or bituminous substances to be distilled.

NEWALL, ROBERT STIRLING, of Gateshead, Durham, wire-rope manufacturer. Improvements in setting up ships' rigging. Patent dated February 4, 1854. (No. 281.)

Claims.1. Forming the holes in the tongues of metal lanyards nearer together, or at a greater distance from each other than those in the two cheeks, for the purpose of enabling the tightening or setting up of ships' rigging to be adjusted to the nicety required. 2. The adaptation of a weighted lever to the screw employed for tightening or setting up ships' rigging in such manner as to measure or weight the strain exerted, and thus regulate the strain in proportion to that which the ropes are calculated to bear.

COLE, EDWARDS, of Hemmning's-row, Westminster, leather case-maker. An improvement in the frames of travelling bags. Patent dated February 4, 1854. (No. 282.) Claim. Constructing the upper frames of travelling bags of angle iron, and connecting the top frames by means of joints, as described.

-

SULLIVAN, THOMAS, of Foots-cray, Kent, roller manufacturer. Certain improvements in rollers and moulds used in making paper. Patent dated February 6, 1854. (No. 283).

Claim. The manufacture of rollers and moulds used in the making of paper, with spaces or interstices therein for producing lines on the paper.

The

MEERE, AUGUSTE LOUIS NICHOLAS COMTE VANDER, of Paris, France. manufacture of artificial whalebone, or a substance capable of being employed as a substitute for whalebone and tortoiseshell. (A communication.) Patent dated February 6, 1854. (No. 287.)

This invention consists in softening horn and rendering it flexible and elastic, like ordinary whalebone. The horns are cleansed from grease, split, opened out, and flattened in the ordinary manner, and then immersed for several days in a bath composed of five parts (by weight) of glycerine and 100 of

water.

HEMSLEY, THOMAS and WILLIAM, of Melbourne, Derby, lace manufacturers. Improvements in the manufacture of looped fabrics. Patent dated February 6, 1854. (No. 288.)

This invention relates to a previous one