NOTES AND NOTICES.

Suspension Bridges. Mr. Dredge has just completed two bridges in Ireland, one across the River Bann, county Down, the other over the Blackwater, county Tyronę. This last is for the Earl of Caledon, and is the second built across the same river-which Mr. Dredge has built for his Lordship within the last year, and the fourth he has erected within the last four months. Two of them are county bridges, and all of them are calculated to sustain a heavier load than can possibly come upon them.

The Iron Age.-It is now upwards of 5,000 years since Vulcan began business: but we question if he ever had so many orders as at present-never so many forges at work-never so many "artificers in brass and iron" to instruct. This is, indeed, "the iron age!" But the poets were not true prophets, who sung of the miseries of mankind during that age; for Midas has touched it, and, by a most potent alchymy, has turned it into gold! Witness the millions accumulated by those men of iron, the Guests, the Craw hays, the Thompsons, the Hudsons, and other millionaires of the present day. Industry, directed by science and skill, is, after all, the real alchymist; by exploring the bowels of the earth, and bringing up to light its mineral treasures, even of the coarsest kind, and by applying them to the commerce and convenience of human life, she enriches and improves the most extensive populations.-Boulogne News.

Dr. Payerne's Diving Bell.-Some short time since, Dr. Payerne descended in a diving bell, at the quay of Orsai, in presence of MM. Mallet and Frisseau, divisional inspectors, delegated, in connexion with him, by the French Minister of Public Works, to assist in experiments for the purification of air by his new process, when the following observations were made:-At 8h. 0m.-water below the mark, 0.76 pulsations per minute, 84; manometer, about one-ninth of the atmosphere? thermometer, 18. deg. At 8h. 12m.-the water below the mark, 0.71. Whilst descending there was merely felt a slight sensation about the eyes, which speedily ceased when the bell had reached the bottom. At 8h. 12m. some of the compressed air was let off, this immediately obtained an agreeable cool atmosphere. With closed cock, at 8h. 14m.-water, 0.80; pulsations, 81; 8h. 32m. water, 0-71; thermometer, 22 deg.; manometer, 9; pulsations, 81. 8h. 47m.-water, 0.64; thermometer, 23 deg.; manometer, 9; pulsation, 81. No uneasiness whatever was experienced, the experimentalists merely feeling a little heated. powerful ventilator in the square part of the bell caused a continual humming. 9h. 0m.-water,

A

0.61; thermometer, 24 deg.; manometer, 6; pulsations, 80. At 9h. 3m., the cock of the compressed air was opened, and the air found cool with an agreeable breeze. At 9h. 9m. the water being at 0.69, no more compressed air was left. At 9h. 17m.-water, 0.62; thermometer, 25. deg.; manometer, 6; pulsations, 82. At 9h. 39m.-water, 59; thermometer, 25 deg.; manometer, 6; pulsations, 82. At 9h. 49m. water, 0.59; thermometer, 25 deg.; manometer, 6; pulsations, 82. Similar experiments were continued till 11 o'clock, when the last observations gave-water, 0.57; thermometer, 25, manometer, one-seventh; pulsations, 86. These results are considered highly satisfactory, and confirmatory of the applicability of the process. For a description of Dr. Payerne's apparatus, see Mech. Mag., vol. xl., P. 1.

Increasing the Adhesion of Railway Carriages by Magnetism.-Dr. Wright, of Pittsburg, has made an application of magnetism to locomotives, which, if successful in practice will be of great importance. It is well-known (says the Pittsburg Gazette) that lo

comotives of great weight are used upon our railroads, made so not for the strength or power, but solely for the purpose of procuring that degree of adhesion to the rail without which friction up-hill cannot be accomplished. Dr. Wright proposes to effect this adhesion by simply, at will, as the occasion may demand, converting by means of galvanism, the periphery of the driving wheel into a powerful magnet. Its application is very simple, and it is calculated that it will give each wheel an adhesive force of two thousend pounds additional to what it has from its weight; it follows of course, that a given force applied in propulsion, will be more efficient, as there will be less weight to be moved, and the tendency of weight having to run down hill instead of up will not have to be overcome in so great > a degree, by mere force of steam.

American Iron.-A Liverpool merchant, who went through the American iron-works in August last, writes as follows:-"Mr. Wemslow, of Tray IronWorks, says that the owners of the Danville furnaces have contracted with the owners of the mills and forges to supply them with their pigs at 11 dollars per ton, or about 21. 5s. of our money; and they have contracted for a supply of coals, which are got close to the works, for 14 dollars, or 5s. per ton; and he says he has no doubt but that, in a short time, they will be able to make their pigs for 8 dollars per ton. You may judge for yourselves, therefore, what chance we have of long competing with these people. Charcoal blooms are now at 50 dollars, or above 10l. per ton sterling." And he adds, in regard to wages-"The average wages of the workmen is about 3s. 6d. sterling per day, paid in truck at the employer's store, in provisions, clothing, &c., for which they pay 25 per cent., and in some cases higher, than they would buy them for at the regular stores."-Scottish Railway Gazette.

Wear of Railway Iron.-From some returns connected with the working of the Lowell Railway, in the United States, we are enabled to give a pretty correct account of the durability of railway iron, 56 lbs. to the yard. It appears that the first ten miles of the second track of this road was first opened in 1838, at which time an H rail was substituted for the fish-belly pattern, which had been found inadequate. From 1838 to July last, a period of seven and a half years, the total quantity of merchandise which passed over the line was about 720,000 tons, and of passengers and goods 120,000 tons-making a total of 840,000 tons, only one-half of which, or 420,000 tons, passed over the second track. In 1844, the company were obliged to remove considerable lengths of these rails, and substitute new; and, from the continuance of these repairs, it is highly probable the whole ten miles will be changed in the course of the next yearthus making its durability equal to 500,000 tons in eight and a half years; the generally estimated wear being 1,000,000 tons. The iron now being laid down is 63 lbs. to the yard, and costs the company about 4,700 dollars per mile. Dividing this sum by 500,000 tons, the amount of traffic which has worn it out, the result is one cent. per ton per mile; and the company receiving five cents. per ton per mile for their freight, leaves them four cents. per ton per mile to cover the other working expenses, interest, dividends, &c.-Mining Journal.

INTENDING PATENTEES may be supplied gratis with Instructions, by application (post-paid) to Messrs. Robertson and Co. 166, Fleet-street, by whom is kept the only COMPLETE REGISTRY OF PATENTS.

MUCH as we have published on the history of Screw Propelling, we find that the subject is still very far from being exhausted. We are now enabled, through the kindness of our ingenious friend, Mr. Bennet Woodcroft, of Manchester, to lay before our readers a document which carries the invention, as a patent subject matter, back to a much earlier date than is assigned to it in popular opinion. It is the copy of the specification of a patent for a screw propeller granted to one William Lyttleton, as far back as the year 1794. Mr. Woodcroft, who, as our readers are aware, is himself an ardent competitor for screw-propelling distinction, (see Mech. Mag. vol. xxxix., p. 293) has been led by the interest he takes in the subject to form a catalogue raisonnée of all the patents granted for, or relating to propelling, from as early a date as 1618, down to the present time, which he is about to publish; and the scantling" we now present to our readers may be taken as a specimen of the value and utility of his researches.

Specification.

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To all to whom these presents, &c.I, William Lyttleton, of Mansel-street, Goodman's Fields, in the parish of Saint Mary, Whitechapel, and county of Middlesex, Merchant, send greeting. Whereas, &c., &c.

Now, know ye, that in compliance with the said proviso, I, the said Wil

liam Lyttleton, do hereby declare that my said invention of a certain machine, which I call the aquatic propeller, is described in the plan and description thereof hereunto annexed. In witness, &c.

Explanation of fig. 1.—a a a represent a hollow cylinder; bbb the sweeps fixed at right angles to the cylinder, and on an angle of 35° with the axis; cc the pivots of the axis on which it revolves in its frame when used; d d is a large sheave with an acute score to prevent the rope from rendering in it when in the act of turning, and has straps for the purpose of fastening it by screws to the inside of the cylinder and the cross bars at the end of it. (See figs. 3 & 4.) 1 1 1, e e e, are thin bars with straps (as at g g), which being secured to the ends of the cross bars (fig. 3, 2 2 2), and the edges of the sweeps support them in their pressure against the water; ƒƒƒƒ are the cross bars (see fig. 3) which are sunk into and secured to the ends of the cylinder; in the centre of them are the pivots c c, and the ends being turned and perforated as at 2 2 2, the thin bars (e fig. 1) are screwed thereto. The bars being made flattish should stand obliquely or parallel to the sweeps, the ends of which are fastened to them; r is part of the endless rope that passes over other sheaves to one at the end of a winch, which is to be turned by men, but may be done far more effectually by means of

a small steam engine. Fig. 2 represents an end view of the propeller with three sweeps.

The number of sweeps should be in proportion to the diameter of the cylinder. Fig. 3 is the cross bars, &c., for three sweeps. Fig. 4 is the sheave for ditto. Fig. 5 represents a skeleton cylinder made of hoops and bars, screwed together, which may (as well as the sweeps) be taken to pieces occasionally.

Note.-The skeleton cylinders are best adapted for use at sea, as they will rise and sink readily with the motion of the vessel.

The frame for the propeller should be adapted to that part of the ship or vessel it is applied at, viz., the sides, or head,

Sir, It is an old saying, that “an angry man has a bad cause,' and from the nature of Mr. Hoseason's reply to the few hasty remarks made by me in No. 1161, it is peculiarly applicable to his case.

I most indignantly deny that I have in any way attacked the "entire members of his profession;" I spoke of the authors of the navy, more especially Otway and himself; and if the mere expression "benighted" can be so widely construed, how small an offence is this compared to the expression of his friend "Binnacle,' "that there is a lamentable degree of ignorance prevailing among Royal Navy men on this subject;" added to which, the tender and kind way in which Mr. Hoseason has introduced sundry officers by name, and exposed them as incapable of understanding the most fundamental laws of science; his accusation against the Lieutenant of the Hydra (p. 264) of something like falsehood or dissimulation; and lastly, his apology and hope that no ill will ensue from what he has done, are far, very far, beyond anything I have said to the prejudice of those gentlemen, and for whom, as a body, I have too high a respect to indulge in any remarks with regard to them that are not strictly true and correct in fact.

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I shall, however, avoid as much as possible this sort of retaliation, and closely adhere to the matter in hand, though I must here remark that my letter barely calls for his uncivil reply-incivility so nearly allied with conceit (which it is always so commendable to put down) that I feel spurred to some little exertion, and trust I shall be able to show your readers that his advocacy of the principle of expansion has been as feeble as his charges against me of "sneering and poking" are purely ridiculous.

Although Mr. Hoseason's letters were originally printed for private circulation only, it was not peculiarly select, and the notoriety which they produced for him in certain quarters appeared to promise some permanent advantages, which we may hope to have been realized, From criticism he was protected, and has remained so, until the recent publication in this Magazine.

That Mr. Hoseason would have exercised a sound discretion in preventing their re-appearance, I am not prepared to deny. Your readers can better estimate mechanical knowledge than those originally addressed.

And what, sir, is really the difference between Mr. Hoseason and myself? I have asked, what does he claim? Has he advanced anything that is new, either in the theory or practice of the expansion of steam? His answer is distinctly in the negative; then what can it be but the "reiteration of known principles" that have been practised with such success by engineers for many years past? I have said, if this was his object, he has the undoubted merit of good intentions, and I fully and freely give him credit for any good he may have done.

I have never in the most remote degree denied the benefits to be derived by the expansion of steam; on the contrary I have sedulously laboured for many years past to advance this truth, though in a far different and more efficient way than that practised by Mr. Hoseason, namely, by experiments of all kinds, and by careful indicator manipulation.

To say the truth, the sole advantage this gentleman possesses over some of his brother officers, is that of a tolerable theoretical knowledge of the properties of steam; and although I commend him for his application and study, which are unusual, I cannot congratulate him upon

the selection of what he calls facts, brought forward to elucidate his various reasonings; they are simply not facts, and there is more or less error in all of them; his want of practical engineering knowledge has led him into many ridiculous fallacies, and he has certainly proved himself incapable of comprehending what he has studied.

I here allude to the "law of the squares" to note that I have not in any way questioned the truth of that law. I am fully content to leave that matter between Mr. Hoseason and the philosophers he has quoted. I have said that the required horse power is as the "cubes of the velocities," a law that has been confirmed by a very extensive practice, and before I have done I shall in many instances prove its correctness. I have not misquoted Mr. Hoseason in any way. I merely drew attention to the fact that when applying the law of the squares to the case of the Phoenix (p. 263,) he stated the square of 9 to be nearly double that of 7 (!) and as an inference was drawn therefrom, I intended it to show the loose manner in which his " points" are proved, and which is neither Russell's nor Lardner's way of doing such things, but all his own.

Mr. Hoseason says, 66 that he left entirely untouched the question of what horse power ought to be placed in a vessel, in consequence of the increased resistance of the water, as it was not, from the line of argument he had adopted, the subject under discussion, &c., &c." No! He advocates throughout his letters "the economic use of fuel by the expansion of steam," and dwells upon the small ratio in which the velocity of the ship, and of course the power, decreases with the reduction of a moiety in the consumption of coals. This is his argument, which, though most verbose, contains some truth-some corn, but mixed up with an immoderate quantity of chaff. This granted, it does not appear to me what necessity there is for entering at all upon the question of the resistance of fluids as an abstract question. We have to ascertain what is the ratio of the power or force necessary to drive a given body through water at a given velocity; and it further appears to me, that must be determined by experiment alone, not made upon models in a horse trough, or other convenient place,

nor upon one or two vessels, but upon many ships of different forms and scantlings.

When I tell him that the "law of the cubes" has been proved by experiments upon more than 200 steam-vessels of varying forms, weights, and powers, this latter being accurately noted by the indicator, (and which power governs and controls all he has argued for,) during a period embracing a practice of 20 years, he ought to be thankful for the information, and certainly courteous enough to withdraw the appellations of "blockhead"* and charlatan, otherwise I must come before you in propria persona, and appeal to the profession for their decision as to which of us has the greatest claim to them.

And now a word about the philosophers. I know something of Lardner, and have the honour of personal acquaintance with Russell, but have not disputed anything they have written; that has been done by Mr. Hoseason, who asserts that they differ in their theories; but this I do know, that they have the highest respect for experimental research. If the law of the cubes is not to be found in any of their books, all I can say is, that it ought to be, and I shall take the earliest opportunity to bring the matter under the notice of the latter individual.

Mr. Hoseason is disingenuous: I was not so absurd as to credit him with the discovery of expansion. I wish to draw the line distinctly where we particularly disagree, and it is this-I say that the whole tone and tenor of his writing would lead a casual or uninformed reader to suppose that he was in advance of the times as to the practical application of

I am not so illiberal as to suppose that any one out of the profession cannot, by study and application, soon master the theory of the steam engine; but on the other hand, it must be allowed, that such an individual, be he ever so talented, cannot be expected to match those who have for years devoted their undivided attention to one object. The amateur is crude in his ideas, wanting experience to temper his knowledge. This is illustrated daily. During our last session of the Civil Engineers, one of the most able and talented officers in the navy made an absurd proposition relative to some fitment for her Majesty's vessels. Respect for the veteran alone smothered the cachinnatory movement that was ready to follow. Again, there is that "satisfactory" affair at Chatham, of which you have more than once so good-naturedly spoken, and the letters now under my notice are instances in point. They are all noble fellows, but a little out of their line, which should be that of battle.