the back bar g, which turns in brass bearings, fixed to the legs of the lathe as shown, and to the end of which is fixed the upright rod d, communicating with the crank e, by the connecting rod f. It will be seen, on reference to fig. 1, that the crank e (which is fixed to the shaft g, at the driving wheel,) has a groove in the middle of it, which allows the pin, to which the connecting rod f comes, to be shifted to or from the centre and made fast at any required distance, as the case may require, by a nut and screw at the back. H. C. APPLICATION OF THE ELECTROTYPE TO THE MULTIPLICATION OF GRADUATED INSTRUMENTS. Sir,-In your last Number, which has just been received, I observe mention made of a new application of the electrotype, by M. Peyré, for multiplication of graduated instruments. As the first to make the subject public, doubtless he has a right to the invention. The method was, however, proposed by me in December, 1840, for producing graduated astronomical instruments from an original 66 DOUBLE ACTING ROTARY ENGINE COMPANY." one; also scales, dials, &c.; and probably Sidmouth, March 18, 1842. N. S. HEINEKEN. DOUBLE ACTING ROTARY ENGINE COMPANY." We learn from some papers which have been forwarded to us that a project is on foot for the formation of a company under the above title, for bringing into use a "new motive power," which is considered to be incomparably superior to steam, and therefore infallibly destined to supersede it every where and for every purpose. "Mighty agent" as steam is, this is represented to be mightier still. To the application of steam there are certain practical limits, but this new power is a power which "can be carried to any extent." The cost, too, is not simply less than that of steam—it is "infinitely less." People may send their present steam engines to the marinestore shops, and obtain as much for them at old metal prices, as will suffice to build them "infinitely" better engines on this new power plan. "The sale of the rejected metallic parts" is to defray "nearly" all expenses of every kind, both present and future. For, once erected, an engine on this new plan is to cost nothing, or next to nothing; "no fuel, of 249 any kind is required"-no "daily maintenance"-it is to work without any "wear and tear," saving only the "mere loss occasioned by friction"-all that is wanted absolutely is, but a little oil or tallow to lubricate the parts occasionally -once a twelvemonth or so! Some of our readers (we hope not many, however) may by this time have pictured to themselves that "galvanism, or electricity" must needs have something to do with this new miracle of invention. No such thing-the mystery lies a good deal deeper. Neither galvanism nor electricity is of virtue enough for the accomplishment of such wonders; and "for this simple reason, says Messieurs the projectors of the "Double Acting Rotary Company," "that they are convulsions of nature never intended by a Divine Providence for the use of man"!! Where then lies the grand secret? In a narrower compass than any thing so extraordinary was ever perhaps shrouded before-in a nut shell verily. You have but to place an empty cylinder, one half in water, or any other fluid, and one half in a vacuo-that is, literally, all you are required to do-and you shall cause it to revolve continually, and with any degree of power you please-remembering only to make your cylinder large enough! And for this other " simple reason:" there are two tendencies to move" in the cylinder the tendency of the part in water to rise, and the tendency of the part in vacuo to fall, and "the two tendencies being auxiliary to each other, necessarily produce a continually revolving motion !!!" 66 The thing is so like a joke, that it may be difficult to persuade our readers we are not joking. We describe the invention, however, with strict fidelity, as we find it described in the printed papers of the projected Company now before us. The inventor and his friends then must have deceived themselves? One would in charity think so; but if they have, it is not at least without sufficient pretence of ability to judge rightly, and without a great display of pains to go on sure grounds. The inventor is a "Count de Predaval," "who styles himself Engineer in the Service of his Imperial Majesty the Emperor of Austria;" and the Count, as a good and respectable engineer worthy of such distinguished patronage would do, has been careful not to submit his inven tion to the public till "after the strictest experimental investigation has perfectly proved its merits." Nay more, with a view to obtain the corroborative evidence of scientific men on his invention, it was submitted to several eminent engineers ;" and a report of "one of them" is given at length, which we are told "vouches for the excellence and applicability of the principle of the invention," as in sooth it does. Who the other "eminent engineers" were, and what they said of it we are not told. The Count, probably, thought that after "one of them," and he, no doubt, the most eminent of the lot, had said his say to such capital purpose, there was no need of further testimony. Would any one, after quoting a Wellington on a point of military skill, think of calling to witness either a Colonel Toby or Corporal Trim? But who is this selected "one"-the most eminent among the eminent-the Count de Predaval's Wellington of engineers? The Report is signed "Edward Lomax," and dated from "2, Queen-square, St. James'spark." We must candidly own that we never heard of the name of "Edward Lomax" before, far less of the engineering eminence attached to it. We live out of the world, however-the Count de Predaval in it, (not without some dark intent, we fear, to make of it "his oyster;") and the Count de Predaval says Mr. Edward Lomax, of 2, Queen-square, St. James's-park,' an 66 "" is engineer," and an "eminent" one, too; and the Count de Predaval is himself an "engineer," and "in the service of His Imperial Majesty the Emperor of Austria," &c. &c. &c. Do not all these things, then, satisfy us? We must in sober seriousness say, they do not. We have no respect for " experimental investigations" which prove impossibilities-things which could never have been proved; and must doubt the mechanical knowledge and ability-if we may not the titles and the "eminence" of those who "vouch" for them. We protest that we never, in all our experience, met with any thing more ridiculous than the pretensions contained in this "Prospectus" of the Count de Predaval; nor any thing more elaborately absurd than the "corroborative" Report of his friend, the Wellington of engineers, "Edward Lomax." The scheme is a veritable perpetual motion, and one of the most if not literally the most-nonsensical and visionary of its class. It may be asked, why, if it be so foolish a thing, we put ourselves to the trouble of this public exposure of it? We will tell our readers why. Had the scheme been left to depend on its own merits, or even on the authority of Mr. Edward Lomax -" eminent" as that individual may be -for acceptance with the public, we should not have thought of saying a word about it, feeling, as we should have done, well assured, that it could dupe nobody. But at the head of the "Prospectus' there are the names of a number of persons paraded, as constituting a "Provisional Committee " for the management of this projected "Double-acting Rotary Engine Company;" and among these there is one name which, if it were placed there with the consent of the owner, would of itself command for the plan the confidence and contributions of thousands. It is the name of one of our most learned Professors of a gentleman of real and deserved eminer.ce for his scientific acquirements, and scarcely more distinguished for academic lore than for practical wisdom, strength of judgment, and keenness of discrimination. Who, knowing any thing of Professor de Morgan, would think of asking whether it was a piece of moonshine or humbug to which he had given the sanction of his name? Or who, with money to spare, would hesitate much about paying down a few pounds to be one of the first hundred" to share with the worthy Professor in the golden harvest of which M. the Count de Predaval offers to make them partakers, and in the "liberal premium" which the said "first hundred are to have into the bargain, for benefiting themselves? Here it is the danger lies: here our reason for bidding all and sundry-beware! We have the authority of Professor de Morgan himself for stating that he never heard of this "Double-acting Rotary Engine Company," till he saw his name at the head of the Prospectus; that he knows nothing whatever of the scheme, or of its inventor, or of any of his associates; and that he utterly repudiates all connexion with them and it. We think our readers will agree with us, that this looks like something more than being selfdeceived. People do not commonly use the names of other people, without their knowledge or authority, for any other purpose than that of wilfully deceiving others, 66 SUGGESTION FOR THE IMPROVEMENT OF MR. PILBROW'S ENGINE. Neither are sham Provisional Committees and sham Boards of Directors such novelties in the annals of public delusion, as to make it at all unlikely that something of the sort may be in course of perpetration here. We do but our duty, at all events, in making public what we know of the case; since every share of patronage extended to bubble schemes is not only, so much diverted from the encouragement of legitimate ingenuity and enterprise, but has a tendency to produce an indiscriminate prejudice against all new inventions, to the grievous injury of many of solid worth and unquestionable public utility. CEMENT FOR SILK HYDROSTATIC PRES- Sir,-In reply to the question of your correspondent relative to a cement for silk, allow me to give you the result of a successful experiment I have recently made. Having an old silk umbrella much rent and worn, and for which there absolutely seemed no sufficient cure but that of a new cover, I caused a number of odd pieces of silk to be cut into ornamental shapes for covering the various rents, and having procured a small quantity of caoutchouc, in the liquid state, as sold by retail, (I got it at a shop near the S.E. corner of Leicester-square,) I spread with the finger upon each piece a thin layer of the cement, as well as upon the corresponding pieces, at the inside of the open umbrella; when dry I added a second and a third coating, after which the patches were applied to their respective places, and found to adhere very firmly. I have had the umbrella in use for some months, and find it absolutely impervious to rain-in fact better than when purchased new; and from the plan adopted in systematically shaping the patches, the effect is rather favourable than otherwise. I avail myself of this opportunity to suggest to your correspondent of Feb. 26, that if at the end of the lever of his velocipede he could contrive to inclose one or more columns of water, so as to bring to bear the principle of hydrostatic pressure, I think he might prodigiously assist his power of locomotion. The astonishing effect of this principle may be estimated from the Bramah press; and although, as a general rule, what is gained in power is said to be lost in time, it appears to me that the objection may be obviated. CASES IN SCREW power. 251 1. Suppose two screws made of metal of the same quality, and passing through nuts of the same thickness, but the threads differing in inclination, and consequently thinner in one than in the other, be opposed in their passage through the nuts by an equal amount of resistance-is the thread of one more likely to break than that of the other? If so, why? since, both being half thread and half space between, there will be the same quantity of metal to bear the resisting force. 2. If a screw with a considerable space between the coils of its thread, produce a certain pressure, with a certain force applied to turn it, will a greater pressure be produced with the same force, if one thread or more having the same inclination as the first thread, be inserted between its coils? WILLIAM SPURRELL. Carmarthen, Feb. 19. 1842. WHICH OF THE COMMON WOODS ARE Sir,-If any of your correspondents can inform me which of the common woods, in boards, stand best without shrinking, swelling, or warping, in an atmosphere sometimes dry, sometimes replete with moisture, and at a temperature varying from 100° to 150° Fahr., I shall be greatly obliged by the communication. I do not apologise for this request, conceiving it to be one of general interest to mechanics. If the answer should be found among the deals or pines, it will be necessary to state the kind. Would kyanising, or any other process, be of advantage? I am, Sir, Your humble servant, SUGGESTION FOR THE IMPROVEMENT OF : Sir,-Permit me to offer the following suggestion with regard to Mr. Pilbrow's engine it is, that a pipe should be added to connect the upper and lower eduction ways, so that supposing the steam-piston to have completed its down-stroke, the steam may be allowed to flow into the top of the condenser, without giving injection, until the pistons are about half-stroke, when the top valve being closed, the remainder of the steam may be made to pass through the pipe into the lower part of the condenser, and condensed immediately. By these means there would be, for half the stroke, a vacuum in the top of the steam-cylinder, and during the whole 252 NEWEST CLYDE STEAMERS. stroke, in the bottom of the condensing Your obedient servant, MECHANICAL CHIMNEY SWEEPING. Sir, I regret to say indisposition has prevented me from answering Mr. Baddeley's communication in your Journal of the 26th ult., under the head of "Mechanical Chimney Sweeping." As I had no object, beyond that prompted by humanity, in bringing my plan for Mechanical Chimney Sweeping before the public, and as I have stated a sufficiency on the subject, and having no particular argument of Mr. Baddeley's to refute, I shall beg permission to leave the discussion at this point, feeling assured, that to occupy your valuable columns further therewith, would neither be interesting nor instructive to your readers. I am, Sir, respectfully yours, JAMES A. EMSLIE. Newcastle-upon-Tyne, March 18, 1842. PREVENTION OF RAILWAY ACCIDENTS. Sir,-In your valuable Miscellany, Part 228, is an article under the title of the "Modern Mechanical Moloch," in which you dilate in strong and deserved terms upon the carelessness and supineness of railway companies respecting the safety of the lives of passengers, and the evident want of means to remedy this dreadful evil. From perusing the above, and from other causes, I have thought much upon the subject, especially as relates to the frightful consequences of concussions, and I feel convinced, that by a proper application of mechanical power these evils may be removed. I have devised a plan for this purpose, and constructed a working model which answers my most sanguine expectations; the principles of which are an improved buffer apparatus, by which a motion of two yards may be obtained; and in connexion therewith a selfacting break, on a very simple principle, both of which can be applied at a very trifling cost. Not being in a position to give to the world the fruits of my labour by a further elucidation of my plan, my object in now addressing you is, with your permission, to make the circumstance known, through your valuable Periodical, to those interested in railway affairs; and if any of your readers should think proper to communicate with me upon the subject, I shall be happy to afford them every information. I remain, Sir, your obedient servant, OLIVER MOORE. Sneuton, near Nottingham. P. S. I have also an entirely new and superior plan of a terminus buffer. NEWEST CLYDE STEAMERS. Sir, I observe in your last Number 971, page 240, a paragraph beginning thus:"What do the champions of Thames supremacy in steam-boat building say now to Clyde-fitted steamers?" and a statement follows in reference to "the theoretical curve" which I (and I venture to say many other of your readers) do not understand. However, I must beg to be allowed to ask, What do the champions of Clyde-fitted steamers say to the fact, that the engines of these fine formed wave line vessels which glide so freely through the water, are consuming from 12 to 14 tons of coal every twenty-four hours more than the Thames-fitted steamers? It has been found that the consumption of the Thames during her run out and home, has averaged 26 tons per day of 24 hours, while the Clyde" and "Solway" are not burning less than 40 tons in the same time. will the advocates of Scotch engines say to this? Here we have engines of the same nominal power employed to propel vessels of the same tonnage, yet one pair costs 141. per day more for coals than the other! What I would again strongly advise the Directors of the Royal Mail Steam Packet Company, to adopt the plan of a log-book, suggested by me in your 958th Number. Those interested in steam-navigation could then judge for themselves, and I am quite sure the London engineers would not object to the result being published. In reference to your observations on the combined cylinder engine erected by Messrs. Rennie, at Mr. Thomas Cubitt's, Thames Bank, I learn that some extensive experiments are being made with this engine, in order to determine the quantity of water passing through it as steam, together with the consumption of fuel and work performed, the results of which I think I shall be able to lay before your readers. I am, Sir, March 23, 1842. Your obedient servant, L. P. |