been done by others, particularly the Hindoos, Arabians, and Italians, many hundred years ago. Although I do not go so far as to implicitly believe Solomon's proverb "that there is nothing new under the sun," yet I willingly admit that it is extremely difficult to bring forward any invention or discovery which may not have had a prototype, some faint resemblance, or which has been in some degree attempted in past years, or even in past ages. I will begin with Mr. Woone's substitute for wood engraving, and shew you and your readers that I many times attempted a precisely similar thing about thirty-three years ago. During the years 1804 and 1805, being then intimately acquainted with some goldsmiths and silversmiths, I often went to their shops, and had frequent opportunities of observing their operations in the precious metals, and in silver plated goods. I observed that silversmiths frequently with a brush spread their work over with a white composition, which on inquiry I was informed was flour and water, with fine whiting, boiled up together and thoroughly mixed; this was always done when they soldered on borders, beads, and other devices of silver, upon silver plated goods, or when they filled hollow plated articles with soft solder to give them'weight, strength, and solidness. On inquiry I was informed that the aforesaid composition was spread over the plated goods, and dried on, to prevent the solder sticking on the surface where it was not wanted; for in that case it would either eat off the silver, or spoil the colour and look of the articles. I had several times observed, that when the whiting composition did by any means get scratched or rubbed off, that the solder would immediately run into the vacancy and assume curious forms; and it was this very circumstance which suggested to me the discovery of coating over polished plates of metal with a wet composition of whiting, plaster of paris, and similar substances, and when dried to trace thereon with a needle or pointrel any letters or drawings. It was the more natural that this idea should occur to me, for there was scarcely a day passed at that period on which I was not more or less visiting printing offices, &c., and had previously seen both wood cuts and copper plate engraving, and had occasionally witnessed the casting of the metallic For types used by printers. I thought at first that I had hit upon something that would prove very useful; and made many attempts upon plates of brass and copper, and also on plates of polished steel: I tried many castings both with soft solder and with type metal, but could never get a cast to my liking of any drawing, even though it were not more than three or four inches square. I found many difficulties in the practice, that could not have been expected from the theory of the discovery; for example, if I wished to have a number of fine lines in the casting, I found it absolutely necessary that the coat of whiting composition should be spread very thin upon the metallic plates; and however thin it was spread, I found that when there was a number of fine lines to be drawn close, it would often happen that the composition would peel off for two or three lines together, so that what should have been three or four very fine lines, formed only one broad and coarse line; and I found that this difficulty was always increased with the increase of thickness in the composition spread over the plates of metal. coarse lines, a greater thickness of the composition was necessary than when fine lines were desired, which still increased the difficulty; and by having the composition spread very thin, although fine lines were produced, there was then so little of depth or boldness in the casting, that the balls in spreading the printing ink over these fine lines, were liable to fill them up, and to touch upon the bottom of the open spaces where the lines were far apart, and thus produce imperfect impressions. And again,after having completed drawings without any of the composition peeling off under the operation of the tracing needle, I have known when the melted metal came to be cast upon it for the intended type plate, that while one part thereof was beautifully cast, in other places large portions of the composition had separated from the metallic plate, and that the casting was thereby utterly spoiled. Making the prepared plate something hotter than the hand could bear to handle, had a tendency to insure a good casting. As before observed, it was extremely difficult to make the composition adhere firmly to the whole surface of the metallic plate: if there was too little flour therein, it possessed little or no adhesiveness; and if too much flour, it would sometimes swell up or become spongy I found that very smooth plates of steel and of iron seemed best for the purpose, as in the course of two or three days after the composition had been spread over them, a slight deof oxidization would take place, which gree had the effect of making the composition adhere more firmly to the iron and steel surfaces, than it would to the surface of any other of the metals. This suggests to me, that perhaps a finely-powdered ferruginous oxide mixed with the whiting and plaster of Paris, might have the effect of attaching the composition more firmly to the metallic surfaces on which the drawings and castings should be made. I have here given a circumstantial account of my attempts at type-plate casting; and the practical illustration here detailed of the difficulties attendant on these experiments, will, I think, without any disparagement to Mr. Woone, if he be a young man, not only convince him that his discovery is no new affair to me, but also that I was well acquainted therewith long before he could have thought of it at all. I only wish that Mr. Woone may be more successful in type-plate casting than myself; and although I have just read the splendid account of Mr. Woone's very ingenious discovery in the Weekly Dispatch of last Sunday, my opinion, founded on personal experience therein, does not incline me to expect the very brilliant performances that some persons appear to anticipate; neither do I believe that it is likely to supersede the long-established mode of engraving portraits and other works of the fine arts on plates of steel and copper. I should conclude it may prove very useful in casting types for mathematical diagrams, such as are found in Euclid's Elements and in other geometrical works where the lines are neither required to be very close, nor yet very fine. Invention of making Lead, Block Tin, and other Metal Pipes, without a Seam and without soldering.-At the opportunities offered by visits to goldsmiths'workshops before mentioned, I had often seen straight parallel slips of sheet silver, brass, &c., turned up until both the edges thereof met, then taken to the draw bench and drawn through the draw plate into tubes, which were often soldered in the seam or meeting of the two edges of the metal. And having seen square ingots of gold, silver, brass, and copper cast, I reasoned within myself, and said, why not cast round ingots of these metals with a core or plug in the middle, which could be taken out when the casting was cold? Thus a great quantity of the hollow tube wire could soon be made that would not want soldering, and would do very well for the joints of tea and coffee pot covers, and of tobacco and snuff box lids. I also thought a great deal of making lead water-pipes by the same process. A few years after, a person, as I was told, about the neighbourhood of Norton Folgate or Shoreditch, took out a patent for the same invention; this I had much desired and intended to have done myself if I could have got the means of procuring the patent: indeed,if the cost of a patent had been no more in England than in America, where the expense is only 87., I should within these last thirty-two years have taken out patents for more than twenty useful inventions. File cutting by Machinery.-About the year 1807, I invented several plans of machines for file cutting, the principal feature of which was a leading screw to each, to advance the cutter, and vice versa, of different degrees of fineness in the thread or worm thereof to regulate the distance between each cut, and thereby determine the fineness of the file. About a year ago, a person took out a patent for file-cutting engines, but I have never seen the machinery. I have still in my possession one of my plans, designed in 1807 or 1808, so that my invention was about thirty years prior to that of the patent just mentioned.* Inventions and Improvements in Steam Navigation. My attention was long ago turned to this department of the mechanical sciences; even in my early youth I thought of propelling vessels by steam; I turned my attention, previous to the year 1807, to the inventing of machinery for this purpose, without knowing at that time that any previous attempts had been made by any other person to effect the same object. My plan resembled that now generally in use, except that the axis * Various patents have at different times been taken out for file-cutting machinery; among others we may mention the names of Nicholson, Cook, Shilton, Vickers, Stocker, and Ericsson. None of these inventions have, we believe, been found to answer, with the exception of Capt. Ericsson's, which is now in successful and extensive operation at one of the first houses in Sheffield.-Ed. M. M. of the paddle wheels had two bevelled cog wheels upon it, fixed upon a collar or socket that would slide backwards and forwards when required, and was thereby brought to act upon either one or the other of two other bevelled cog-wheels upon the axis of the fly-wheel, by which arrangement the motion of the paddlewheels could be instantly reversed. After three or four weeks, I may have more leisure and opportunity than at present, and will call on you, Mr. Editor, and show you a letter which I received in the year 1808 from the highest scientific authority in the kingdom,* being a reply to my proposal for navigating ships by steam; in which the very learned and illustrious personage told me that he could not hold out any hopes of the suecess of such a project, as various attempts had been made to accomplish the same purpose, but they had all failed; for, he said, it was not possible to make machinery strong enough to resist the rough waters of the ocean, &c. Thus we see titled persons, holding high offices, imbued with learned prejudices, are always ready to retard the march of useful improvements; it was thus in the year 1808, and is so still in 1838. Therefore, Mr. Editor, neither yourself nor your readers need be surprised when I state, that some of my inventions for steam navigation, designed by me these twenty years past, although superior to anything yet in use, as you may judge from the certificates ĺ sent you on the 26th of last month, still remain neglected for want of means, and may perhaps be forgotten, though my engines would not take up half the room, nor consume half the fuel, that the same power engines do, on board the very best steam-ships that have ever yet been constructed in this kingdom; and would, in such a ship as the Great Western, enable her to carry about 750 tons more, in freight and passengers, than on the present plan. Loss of Power by the Cranks of Steam Engines. I do not know of any publication having so great a number of very intelligent and talented correspondents as the Mechanics' Magazine; and though I have the greatest respect for their ge * Perhaps our correspondent will favor us with a copy of the letter referred to.-ED. M. M. The certificates were from good authorities, and were certainly very favourable. Eo. M. M. neral skill and intelligence, I must beg leave to remark that some of them do sometimes appear to write in great haste and upon the impulse of the moment, and thereby take either a partial or limited view of the subject under consideration. In reply to your correspondent" W. H. T." (in No 771) who very justly remarks upon the long circuit that the crank pin makes compared with the length of the stroke of the piston; I hope he will not feel offended when I assure him that I am as perfectly acquainted with that circumstance as himself or any engineer in the British Empire; but I must remind him that the circumference of the circle, and the leverage of the crank under different positions during its revolution, are totally distinct and different matters in mechanical science, and must not be confounded or mistaken one for the other. I could hardly help smiling at the remark of W. H. T. when he says there is a want of greater nicety in caleulating the length of the leverage or average of the sines. To this I beg leave to observe, that the numbers, or natural sines, which I have taken from Hutton's Tables, are SO very correct, that they will give amount of leverage to the thousandth part of an inch, even if the crank were ten feet in length. Were I disposed so to do, I could easily demonstrate that, considering its extreme simplicity, the crank is the most efficient mechanical contrivance extant; and I could further prove, that the amount of its performance would be on a par with various other contrivances; yet this is no argument that it might not be dişpensed with, and something better substituted for it. That which my essays have endeavoured to prove, is, that its power is not equable, and that, in consequence thereof, the amount of that power is not near so great as it has generally been thought to be. Reply to Objections on Davenport's Engine.-In No 772 of your Magazine, a gentleman of Manchester, who signs himself F., states what he considers very great objections against the powers and velocity that I have assigned to Davenport's Engine in No. 763 of your publication; this gentleman particularly objects to the great velocity of the wheel and he thinks it cannot exceed ten feet per second. He says that no increase of power can arise from increasing the diameter of the wheel, "and that its power will depend entirely on the size of the magnets." The last thirteen words only, quoted from this gentleman are a perfect truism; but take the bearing and import of the whole quotation together, as above given, it is one mass of error. This correspondent has taken a very hasty, partial, and narrow view of the subject, and has totally overlooked some important considerations which should not be lost sight of: viz. that I had founded my calculations on the proportions and powers of Mr. Davenport's working model engine, as given by Mr. Davenport himself or his friends, and contained in No. 736 of the Mechanics' Magazine; secondly, that the velocity was not stated by me at all as the result of any calculations of mine, but is taken as a matter of fact from the statements of Mr. Davenport, who positively asserts that the wheel revolves one thousand times per minute. If a wrong statement has been made, I ought not to be blamed for that. But let your correspondent F. recollect, that if the statement be true, that the wheel turns round 1000 times per minute, although only six inches diameter, its velocity will by calculation be found to be 18,849 inches, or 1570 feet per minute, which is twenty-six feet six inches per second, nearly three times the velocity which F. says it is possible for the wheel to attain. Why F should limit the velocity to 10 feet per second, he has not made satisfactorily appear to me; for as far as I have observed, it appears to me, that the effects of magnetism and electricity travel with the velocity of lightning. Thirdly, if your correspondent had closely examined my calculations and the dimensions I had given, No. 763 of your Magazine, he would have seen that there was such an increase in the galvanic batteries as was proportionate to the size of each wheel, and sufficient to act efficiently on magnets of a magnitude capable of acting with all the power required upon the wheel, however large the wheel might be; I can assure Mr. F., that if the wheel was increased to certain dimensions, that all other parts of the engine were hy my calculations allowed to be increased in the same ratio. the Fourthly, if F. had carefully examined those calculations, he would soon have discovered that I had allowed more than ten times the battery power that Mr. Davenport asserts would be sufficient to impel a great ship across the ocean; for Mr. Davenport is reported to have stated that a battery as big as a moderate sized barrel, consisting of a few thin sheets of zinc and copper, would be sufficient to drive a large ship over the seas. I smiled when I read this assertion, for really I did not believe it; such powers appeared to me as surpassing magic itself, and this was the cause of my making the aforesaid calculations, and soon convinced me that Mr. Davenport himself had not made any calculations at all on the subject, but had been influenced by hope and guided by conjecture, in his asserting that a battery the bulk of a moderate sized barrel, and a few sheets of zinc and copper, would be sufficient to propel a ship. I found by mathematical calculation that this was totally impossible, and that by comparing the dimensions of the batteries of his working model engine, with one the size of a bar. rel, that the increase of power to do this, would be far beyond any increase of power to be obtained either by the squares or cubes of the given dimensions; and therefore it would be quite irrational to expect any such great power from so small a battery. In fact, I found by my calculations, that it would require about 6500 superficial square feet of sheet zine and copper to perform this. I have not my calculations by me just now, but I believe, from recollection, that this is very nearly correct. Önce for all, let me most respectfully assure your very numerous readers, that if the performances and dimensions of Mr. Davenport's working model-engine have been truly reported by him and his friends, then they may rest well assured that my calculations will give the sizes and capabilities of the engines which I have described in the former numbers of your Magazine; but also let them remember, that those persons who draw their judgments from supposition or conjecture, will always be found to differ widely from the conclusións founded on mathematical calculations. In conclusion, I will here remark, that if I do not shortly hear of some more satisfactory details and more minute descriptions of Mr. Davenport's engine, I shall begin to suspect that there has been very gross exaggeration and much misrepresenta tion from our Transatlantic friends concerning the powers and performances of this invention. I remain, Mr. Editor, Teacher of Mathematics, &c. 30th May, 1838. TOUCHING VARIOUS MODERN IMPROVEMENTS AND DISCOVERIES. Sir, Far be it from me to say to the stream or tide of improvement, "hitherto and no farther;" but on the legitimate grounds of discovery itself, there may be a right and a wrong application, and this is all I bring to the "rack" or the "question." To illustrate my position. I think asphaltum a very notable article of combustion, and, as fuel, a very useful one; but to pave our streets withal, here, indeed, is madness "without method." What could save our towns and cities from total destruction by fire, in such a case as this? Our streets would become lava torrents of liquid fire, as difficult to extinguish as the "Greek fire" in the olden time. Nay, the meteor in the thunder storm might kindle it, and the fate of the "Cities of the Plain" be ours, though the judgment in their case was specific and penal. Harper and Joyce's "wonder" is a parallel example; but the expence they have recklessly incurred is sufficient punishment, if none in the mean time have indeed fallen victims to their ignorance of the principles of chemistry. A few experiments satisfied me of the dangers of their pretension; and I will confess, that though a firm and unflinching advocate of the superior salu. brity of open fire-places, I must say, that I think Dr. Arnott's invention one of the best I have ever seen. Dr. Arnott is an elegant writer, and a clever and judicious man. Though you may, Sir, pronounce my mellange "de omnibus rebus et quibusdam aliis," I pray you to allow me a paragraph for Perkins's pipes. These "heaters," as they have been called, I never could attempt to approach except when they ceased to be so, and the fire beneath had been long withdrawn. The very idea of "red-hot water" terrified me and inflamed my fancy; we cannot account for these idiosyncrasies, but so it was. "The proof," &c.-it is a homely adage, you can finish the sentence, and know the commentary. Well then, permit me to ask, is there any one that has ever used these Perkins's tubes, pipes, or heaters, but would be most heartily glad to get rid of them? I fear, as far as my knowledge extends, I must answer by a decided negative. In the Manchester Botanic Garden, they burst, set the place on fire, and destroyed property to the amount of more than 300l. You therefore see, Sir, that my opinion, recorded in your former pages, was a valid conclusion, formed on a solid basis. I am, respectfully, Sir, London, June 11, 1838. J. MURRAY. INDIAN STEAM NAVIGATION. 66 Sir, I am sorry that Mr. Bayley (page 150,) should have found matter of offence in the few remarks I hazarded on his letter relating to Indian steam navigation, especially as his thanks rather than his resentment, might have been expected for calling his attention to the article on Messrs. Seaward's scheme in vol. xxi, so unaccountably overlooked by him, notwithstanding his qualification as a constant reader" of the Mechanics' Magazine. Far from wishing to insinuate that there was any thing in Mr. B.'s "conduct" not "consistent with propriety," my sole intention was to impugn his " opinions" as to British supineness in the matter of steam navigation in the East, and to point out a few of the many facts militating against his sweeping condemnation of his countrymen's inactivity. That these facts were quite conclusive, is evident from every paragraph in Mr. B's. last letter, which, indeed, would seem to have been written only to amplify and confirm them. How stands the case, according to Mr. Bayley's own showing? Simply thus. The Dutch, the active Dutch, are building some steam-vessels in the East; the English, the backward English, have only five steamers already on the spot, and three more building at home "expressly for the service." This, surely, is enough to quiet any immediate |