418 MR. CHILD'S ELLIPTICAL DIVIDING APPARatus. DESCRIPTION OF AN APPARATUS FOR DIVIDING THE PERIPHERY OF AN ELLIPSIS INTO EQUAL AND EQUIDISTANT LOOPS. BY MR. K. CHILD. The wheel A (fig. 1, front page) is fixed to the frame SS, and has an axis passing through it, to which is secured the oblong frame MM; B has only half the number of teeth that A has; D is fixed on the axis of the wheel B, and has the same number of teeth that Chas; B is made to revolve on A, by turning the handle I. The axis of this handle carries the frame round, in which the wheels C and D are, at the same time, turning on their axes. It is evident, from this combination, that a tracer, properly fixed to the axis of the wheel C, will describe an ellipsis. The socket K is fixed to the underside of the frame, so as to be concentric with the wheel C, and on this socket is placed the wheel E, with its grooved lever L, which is screwed to the upper side of the wheel E. The frame NN is fixed on the axis of the wheel C, and the axis of the wheel D carries the adjusting screw e, and the slide, which works in a dove-tailed groove, in the under-side of the socket m, and which has in it the pin o, playing in the groove of the lever L. This pin may be set, either concentric with the wheel D, or at any given distance from the centre of its motion, by the adjusting screw e. When the pin and axis of the wheel D are concentric, no effect is produced by the pin o on the wheel E; and a tracer T, fixed to the axis of the wheel G, will, by means of the wheels E, F, H, and G, describe loops, closer at the ends of the transverse than at the ends of the conjugate diameter: but if the pin o be not concentric with the wheel D, it will alternately accelerate and retard the motion of the wheel E twice, while the tracer T is describing a complete figure; and, by means of the adjusting screw the e, loops may be made equal and equidistant, be the size or eccentricity of the ellipsis what it may. The tracer T is movable in the axis of the wheel G, and can be fixed by a small screw. The above represents a part of the delineating apparatus by which all the figures were produced that have, at different periods since January 1825, been transmitted to the office of the "Mechanics' Magazine." I am, Sir, Your most obedient Servant, K. CHILD. Remarks by the Editor. The preceding communication was transmitted to us by a friend of Mr. Child's, who adds from himself: "The drawing exhibits Mr. Child's model as it is now set for the purpose of producing the equal division of the oval; and I can, and will, if required, produce evidence of its being exactly in the same setting in 1825, when some figures were drawn by it which were sent to you in that year." " The "figures” referred to as having been sent to us in 1825 (1826?) are among those specimens of Mr. Child's performances which we announced some time ago were deposited at our office for the inspection of the curious. We should not, however, be dealing candidly by our readers, were we to leave them to suppose that they do actually prove the fact for the purpose of establishing which reference is here made to them. As we have said more than once before, they exhibit approximations only to the equal division of the elliptic curve. Mr. Child affirms, in the preceding description, that "by means of the adjusting screw e, the loops may be made equal and equidistant, be the size or eccentricity of the ellipsis what it may;" but it is most certain, that none of the specimens he has hitherto sent us prove any such thing. Now, in the book of Mr. Ibbetson's specimens, which lays also at our office for inspection, there are many examples of ovals divided into equal and equidistant loops with the most perfect exactness; so perfect, that it is not possible, even with the aid of a powerful microscope, to discover the slightest disparity between the loops. Fac-similes of two of these examples were given in our 294th Number. Mr. Ibbetson has frankly admitted that he does "not dispute Mr. Child's knowing the principle on which a perfectly equal division of the ellipsis is to be effected," (see a letter of his, quoted p. 106, vol. xi.); but he adds, what, we are bound to say, is in accordance with every thing we know of the matter of fact, "I say he has never yet actually MR. CHILD'S ELLIPTICAL DIVIDING APPARATUS. divided an ellipsis into equal parts; he has never thrown the looped figures at equal distances in the curve of an ellipsis." It is, besides, only fair to Mr. I. to observe, that until he made public the power of his geometric chuck to divide the periphery of an ellipse into equal parts, neither Mr. Child, nor any one else, ever laid claim to the invention of any instrument possessing that power. Such, at least, is our impression of the state of the case; if we are mistaken, it is an easy matter of proof to shew that we are wrong. The capabilities of Mr. Child's apparatus are admitted on all hands to be extraordinary. Mr. Ibbetson was himself the first to point out that it can produce figures which are not within the range of powers possessed by the geometric chuck-those of a cycloidal and spiral form for example. But Mr. C. should not endanger the praise which is so justly due to him for having accomplished so much, by laying claim to a power of accomplishing every thing. It seems quite plain to us, from a comparison of the productions of the two instruments, that Mr. Ibbetson is in possession of some means of adjustment or compensation, as regards the equal division of the periphery of an ellipsis, which Mr. Child has yet to discover, or, at all events, to reduce to practice. And we feel well assured, that if Mr. I. would be only as communicative as Mr. Child has been, he could in an instant place this fact beyond the possibility of dispute. It is a pity he is not as communicative. It is something to be able to say that one can do what no other person can; but the praise most to be desired is that of being the first to make a useful invention known to all the world.* It is fit Mr. I. should know, that Mr. Child is not the only person whose close approximation to the equal division of the elliptic curve makes it probable that his secret is in considerable danger. Mr. Chapman, of Whitby, who sent us the remarkable specimens of turning published in our 285th Number, *We understand, that though Mr. Ibbetson has not thought proper to publish any description of his geometric chuck, he has lately confided the construction of it to an eminent machine maker, and authorised him to supply amateur turners with chucks on the same plan, 419 has lately transmitted to us a block engraved by his apparatus, which exhibits an oval divided into loops and circles with much greater exactness than any of Mr. Child's patterns. We shall lay this, along with a letter of Mr. C.'s on the subject, before our readers in an early Number. Following this, there is also a second plan of Mr. Child's, according to which, if correct, the periphery of an ellipsis may be divided into any number of equal parts by a mere addition to the common lathe. Mr. Child informs us that he found it among some old papers, and has never actually tried it; but that he has no doubt of its producing the effect intended. August 12, 1829. After the preceding remarks were in the printer's hands, we privately communicated the substance of them to the gentleman who was the medium of transmitting to us these last communications of Mr. Child; and we have this day (just in time) received from him a packet of proofs on the subject in dispute, which has produced in us, as we doubt not it will in our readers, a considerable change of opinion as to the capabilities of Mr. Child's apparatus. The writer says, that "Mr. Child does not wish to contend that he ever did actually make a perfect division" (of the elliptic curve); which confirms what we have always asserted, that none of the specimens Mr. Child formerly sent us exhibit more than a mere approximation to it; and his inability to do so he ascribes to certain imperfections in the workmanship of his apparatus. (Mr. C.) only contends that he had the principle, and he is satisfied with Mr. Ibbetson's admission to this effect." "He But though Mr. Child has not himself accomplished this perfect division of the ellipsis, the writer affirms that he has, by the addition of Mr. Child's method as given to the public in our present Numberto a common oval chuck, engraved blocks which " are very nearly perfect" in this respect; and in evidence of this he has sent us the blocks themselves, that they may be introduced into our pages, and speak for themselves. No. 1 is a specimen of ovals divided in their peripheries by straight lines. The division of the third line from the outside is particularised as being "perfectly correct." No. 2 exhibits the periphery of an oval thrown into equal and equidistant looped circles. No. 2. No. 3 is a more complicated specimen, of the same kind as No. 2, exhibiting within the oval an inner set of unequal circles, produced by the same means by which the equal division of the oval itself is effected. MR. CHILD'S ADDITION TO THE COMMON LATHE, &c. 421 No. 4 is but a simpler edition of No. 3. No. 4. Now, it must be confessed, that in all these specimens the division of the periphery of the oval is not only "nearly perfect," but something so like perfection itself, as to leave little, if any thing, to be desired. We have said that they are represented as having been produced by the "addition of Mr. Child's method to the common oval chuck;" but our correspondent adds a slight qualification to this statement. "I make an improvement," he says, 66 on his (Mr. Child's) method, which is, that instead of a groove in the wheel, I screw on the wheel a piece of steel with a groove cut in it, longer than the diameter of the wheel, which increases its power very much." Mr. Child has, it seems, no fewer than five other methods of compensation, in addition to the one which we publish in our present Number, and drawings of these are promised to be sent to us soon. The opinion of our correspondent, on a review of the whole matter, is, that this is but an additional instance to the many on record, of two ingenious individuals hitting upon the same thing, without any knowledge of each other's proceedings. He maintains that there is no part of Mr. Ibbetson's geometric chuck which was not previously known to Mr. Child; but it seems to be as little his intention to detract from the merit of the one gentleman as from that of the other, on account of this accidental coincidence. DESIGN OF AN ADDITION TO THE Having turned an ellipsis in the usual way, fix a wheel (see fig. 2, front page), of ninety-six or any convenient number of teeth, firmly on the pulley of the spindle, and another, of half its dimensions, on the gantry or lathe-head, so that the less may work in and give motion to the larger. Let a straight groove be made through the smaller, from nearly the centre to within a short distance of the circumference. Fix a circular plate, so that its centre can be placed at any required distance from the centre of the smaller wheel. This plate must be divided into only half the number of equal parts into which you purpose dividing the ellipsis; and it must also have a pin fixed upon it, to play freely, but without shake, in the groove. When, therefore, the centre of the plate, and that of the small wheel, are fixed to the eccentricity of the ellipsis as produced by the lathe, by turning the plate, just as you would the dividing plate of an eccentric chuck, so as to receive a catch into each of the before-mentioned divisions, the ellip→ tical circumference will, in conse quence, be divided as required. IRON SHEATHING FOR SHIPS. The failure of the late lamented Sir Humphry Davy's plan for the protection of the copper sheathing of vessels, has left it still an important desideratum to discover such a metallic compound or combination as will exclude foulness and corrosion. The plan of Sir Humphry Davy, as our readers are aware, was to protect the copper sheathing by means of nails, or strips of iron or zinc; it having been ascertained, by numerous experiments, that, by placing a small portion of any metal, which is difficultly oxidable, in sea water (as iron and zinc), in combination with a larger portion of another which is less so (as copper), the one extends a sufficiently protecting inodioH dgi pense to the other. We have spoken of this plan as if it had been "" a 422 IRON SHEATHING FOR SHIPS. failure;" but we believe we should describe the real state of the case more correctly were we to say merely that it did not succeed to the full extent at first anticipated, and was, on that account, very precipitately and injudiciously abandoned. It has always seemed to us to be a case in which, to use the words of Mr. Children, the theory is so obviously correct, that whatever difficulties might occur in the earlier attempts to reduce the method to practice, there must be certain circumstances which, when once discovered, would ensure complete success." We have now before us a new and improved" plan of sheathing, which, though it does not profess to have any reference to the experiments of Sir Humphry Davy, is evidently no more than an application of the principle developed by that eminent philosopher. It is the subject of a patent which was taken out, a month or two ago, by Professor Pattison, of the London University, and was qualified on the score of originality by the very common salvo of its being the result of "a communication made to him from a foreigner residing abroad." Professor Pattison should let the English public know who this foreigner is; and when he has done so, he will still have to justify himself to his countrymen for being the medium of a foreign experiment on English credulity. As a scientific man, Professor P. could not but know well the experiments of Sir Humphry Davy on this subject; and it would have been no more than an act of common fairness to have recognised them in some shape or other. Professor Pattison's "new and improved" method consists simply in using iron instead of copper for the principal sheathing, and strips of zinc, in the proportion of 5 to 100, as a medium of protection to the iron. A great number of directions are given as to the mode of arranging this combination of zinc and iron; but it is not pretended that these are the result of any experiments made on the subject, and many of them bear internal evidence of being entirely fanciful. It is admitted, that "though in this specification the proportions of zinc and iron to be used are stated to be about ed bad it as asiq and to as 5 to 100, for preserving the iron fastenings and sheathings of ships and other vessels, yet it is not indispensable that so large a portion of zinc should be used, and a larger proportion than 5 to 100 may be adopted, if desired." That is to say, neither Professor Pattison nor his convenient "foreigner" can tell whether the proportion should be 1, or 5, or 50, to 100. All that they know is, that zinc will, in some proportion or other, protect iron from oxidation; and for this piece of knowledge, common to thousands as well as them, they modestly claim a monopoly of the use of iron and zinc in the sheathing of ships for fourteen years to come!!! MECHANICAL CHIMNEY SWEEPING. We have great pleasure in bringing under the attention of our readers a report which has been recently issued by the Committee of the Society for Superseding the Employment of Climbing Boys. It is one of the most gratifying which has yet emanated from this very humane association. The committee state that since they have proceeded on the plan of promoting the adoption of Glass's Improved Sweeping Machine (described in our 243d Number) throughout the country, by means of auxiliary associations established for the purpose, 66 feelings of sympathy have been happily roused for injured infancy, which were too long dormant," and "a benevolent disposition to abandon a system as barbarous as unnecessary, is spreading widely and rapidly throughout the United Kingdom." Of the introduction of Glass's machine into the royal palaces and government offices, our readers have been already apprised. It appears that in consequence of the high patronage thus obtained for the machine, it is now in so much request that the establishment of a person * at the west end of the town, in co-operation with Glass, has been found necessary. The charges for sweeping by the machine are the same as for sweeping by * Robert Day, No. 13, Newton Street, High Holborn." |