pinion on I causes M to revolve in a contrary direction, so that M and H move round in the same course, but M turns twelve times quicker than H, or once in an hour. I shall have something more to say about this presently. I think you will understand the construction of the clock better if the separate parts of the train be first explained. Beginning with the largest wheel-viz., the great wheel-the first part of importance is the axis, or arbor, as it is technically termed. Fig. 3 shows this part separately; a b is a small spindle, solid with the rest of the arbor, and upon which the spindle and wheel of the mixute-hand are fitted, so that they may be turned round when it is necessary to alter the clock, and yet have sufficient friction with each other to admit of the wheel, as seen at M, Fig. 2, driving the intermediate wheel I, which turns the hour-hand wheel H while the clock is going; b is an enlargement of the arbor to fit the hole in the movable piece c, Fig. 2. This part is made large, to give it sufficient strength to carry the weight, being only made of wood. The arbor is still further increased in size at d, for the winding pulley; at e, it is made square to fit the centre of the wheel; f is the pivot, which is a piece of steel wire, 1-16in. diameter. Fig. 4 shows the spindle for carrying the minute-hand in its place on the great wheel arbor. The end of the spindle a projects a little beyond the extremity of the hand spindle, to afford room for a thin brass washer or plate, and a cross-pin is passed through the end of the spindle a to prevent the hand-spindle working off. Fig. 5 represents the arbor, winding-pulley, and wheel complete. The winding-pulley is so contrived that, supposing the clock to have run down, we can by pulling the opposite end of the string to which the weight is attached, wind it up, the pulley turning freely round, but if we release the string the pulley will not turn in the opposite direction without carrying the great wheel with it. This is contrived in the following manner :-Fig. 6 is the winding-pulley, which is made of wood, and has a deep groove all round for the line or cord which carries the weight; the groove is notched, as seen in the engraving, to afford the line a better hold, the line only hanging over the pulley, as seen in Fig. 2. The edge of the pulley next the wheel is notched all round like steps, in shape resembling badly-formed saw-teeth, one side being upright, while the back slopes down. Attached to the side of the great wheel is a small spring and catch, Fig. 7. The spring & is fixed in the wheel at one end, the other extremity lodging in a notch at the end of the click or catch e, which is attached to the rim of the wheel by a pin, so that it may move freely. When the pulley is turned round, so that the inclined faces of the ratchets or teeth pass under the point of the click, the weight may be raised without affecting the great wheel, but directly the string is released the weight comes into play, tends to turn the pulley in the opposite direction, consequently the upright part of one of the ratchets coming in contact with the end of the click arrests the pulley, which then transfers the influence of the weight through the click to the great wheel, which is thus turned round. Fig. 8 shows the click and spring separately to a larger scale. Fig. 9 represents the great wheel unencumbered. PIERRE. (To be continued.) HOW TO MAKE AN EIGHT-DAY CLOCK. is a gulf beyond, impassable, because infinite, and that final causes or the essences of things lie beyond that gulf, and for ever beyond the reach of man. More than this, for myself I think that each such advance shows us more and more plainly that we can only form even a faint conception as to causes, by recognizing that all things spring from living will, that speculating on mattere and forces without reference to that higher essencg we call spirit, is very much like the surgeon expectin to learn the secret of life by dissecting dead bodies which are merely its machinery. If it be deemed that I have thus rather stepped beyond the point, let me say that this idea in itself tells us that causes are unattainable to us because spirit is beyond our conception and analysis, just as life is beyond the grasp of the surgeon's forceps, and it is well to recognize the limits by which our powers are bounded. This, however, by no means leads to Mr. Barwick's conclusion (p. 114). We may rightly seek for a physical reason for the earth's revolution; it is no doubt due to a cause, and a cause or action quite within our reach, though we do not yet know it, but when found it will not be the final cause, it will only be one of the actions of some canse, which, however we may trace it back step by step, will yet for ever leave us at a point utterly beyond our conception. SIGMA. HOW TO MAKE AN EIGHT-DAY CLOCK. [658] SIR,-Fig. 1 is a portrait of our old friend "A Kitchen Clock," which though not ornamental is more trustworthy than many with handsome exteriors. Let us take the clock from the nail on which it hangs, and examine its interior economy. This is easily done by simply unlatching and turning back the doors at the sides, as seen in Fig. 2. A A is a wooden frame about gin. thick, strongly morticed and tenoned together; C is a movable piece about 14in. wide, for supporting the front pivots of the wheels; of this I shall say more presently. D is the dial, and B the backboard, by which the clock is suspended against the wall. The wheel work, or train, as it is termed in clock-making, is as follows:-G is called the great wheel, and turns round once in an hour; it is therefore employed to carry the minute hand. This wheel has 56 teeth, which ngage or gear with the pinion P of the second wheel S. The pinion having 7 teeth, or leaves as they are called, the second wheel will revolve eight times while the great wheel goes round once. The second wheel has also 56 teeth, which gear in another pinion P of the escape or 'scape wheel E. This pinion has also 7 leaves, so the 'scape wheel turns round eight times to once of the second wheel, consequently the 'scape wheel revolves 64 times, while the great wheel turns once in an hour. The 'scape wheel has 36 teeth, which are, however, very different to those of the other wheels, being in shape much like the teeth of a hand saw. This wheel is called a 'scape wheel because every time the pendulum swings from right to left, and vice versa, one tooth escapes past a peculiarly-formed piece of metal P called the pallets, which, by suddenly catching the following tooth to the one just escaped, causes the sound popularly called ticking. V is the verge, to which pallets are secured, and by which the impulse imparted by the 'scape wheel is transmitted by the crutch F, F to the pendulum. Before going any further I may as well say that the sole object of the train or wheel work is to supply the slight force necessary to keep the pendulum swinging; in fact to replace the loss arising from friction at the point of suspension, and the resistance of the air. It is not the train but the pendulum that keeps the time, the train only supplying the loss arising from the causes just mentioned, and registering, by means of pointers or hands, the vibrations of the pendulum. The train, I have just explained, would be insufficient, unless people were satisfied with only a minute hand, which would be very inconvenient, because you could only tell the duration of one hour instead of twelve, as you can with the hour hand, which in olden times was solitary, until some improver thought the minute hand was required to assist in determining the number of minutes which had elapsed since the quarter or halfhour, as shown with sufficient accuracy for ordinary purposes by the hour hand. This second train, or dial work, is situated, as you may see, between the movable piece C and the dial D. M is a small wheel, having 24 teeth, gearing into another wheel I of 24 teeth, which latter, with a pinion of 4, drives the hour hand wheel H, having 48 teeth, and turn in the same time, the only difference, of course, being that they turn in opposite directions; but then the STEAM GUNS-PERKINS AND BESSEMER. [659] SIR,-I see my old acquaintance, Mr. Henry Bessemer-whose beneficial public service in the matter of purifying crude iron by a cheaper and more convenient method of applying oxygen to it when molten is one of the most striking modern instances of the social advantages which result from the existence of patent rights, for but that he had been enabled thereby to obtain a temporary property in his invention we could hardly expect that he would have devoted his great abilities to what soon becomes exclusively our advantage-has resuscitated the old steam gun in his letter in the Times of Oct. 13. Assuming his statements concerning the propelling power of what is comparatively low-pressure steam to be correct, his letter is indeed, in these days of mitrailleuses, breech-loading muskets, and riflemen (who John Bull mistakes for soldiers), the word in season. Steam guns are no novelty. When powder is burned much high-pressure steam is formed just as it is wanted; could we do the same, i.e., generate the required quantity to fill the cylinder at each stroke, we might dispense with that most dangerous condition of steam power, the boiler? In one sense, all guns have been said to be steam guns, but the term is commonly restricted to those in which steam alone is employed, and the earliest I remember were those constructed under the direction of Carnot, for the defence of Paris, so probably the French will-as they usually do in most things-claim their invention. The French seem also to be the first people who will use them in war, for it is said they have ag tin constructed several for the defence of their capital against the attempts of the Germans to storm it, for which purpose (if the supply of steam at the required pressure can be kept up) steam guns seem especially suitable. Carnot's steam guns were kept secret, and when the Allies entered Paris they destroyed his "infernal" contrivance. By the way, every novel means for human destruction is "infernal" until-like the live eels which nature, foreseeing their fate, so benevolently provides with numerous cuticles, so that they become accustomed to skinning, and learn rather to enjoy that humane process-we are used to it. Doubtless if history was not silent we should find the first stone cast from a sling, the first javelin thrown by hand, and the first arrow shot from a bow to a distance, would have been success sively recorded, just as villainous saltpetre was, as being the "infernal" inventions of the evil one, who is popularly designated "Ancient Nicholas," and described as most unwarrantable departures from the humane and time-honoured practice of breaking each other's crania and knocking out each other's brains with knobkerries or those yet ruder clubs which mankind appear to have habitually indulged in, "holding to that use," as our lawyers would say, from the most remote prehistoric times until this day. Mr. Bessemer says 1,000 bullets may be shot from a single barrel per minute. Quite true, if you can only put them into it as quickly; but the question arises how far will they be projected if more than one be in the barrel at the same time? duce his bullets at this rate I leave to his remarkabe How he proposes to introability in adapting means to ends, for I am modest enough to confess I don't see how to do it. Should it be found too difficult in practice, even for a Bessemer, we need not despair. We have only to convert our steam gun into a five or six shooter, and then the introduction of only 200 bullets per minute would be needful, no difficult thing to do. My old friend, Jacob Perkins, did considerably more than that, and talked of shooting from a single barrel 800 common musket balls per minute-certainly these are much easier forms than cylindroconidal rifle projectiles to get into the barrel-but I never saw him do it. Now seeing is believing. Mr. Bessemer also says that a bullet propelled by steam at 150lb. pressure would-with proper arrangements-acquire nearly the velocity with which such steam would rush through a pipe into the atmosphere. Very probably this would occur if you only make the pipe (gun barrel) long enough. I think from 40ft. to 50ft. long would be needful; how it could happen in a short barrel I cannot conceive, and what Mr. Bessemer considers proper arrangements he has omitted to state. I may remark, Jacob Perkins (who certainly had very considerable experience in steam guns) felt so strongly the need of subjecting the projectile to the impelling force for a considerable time, that he used a barrel about 6ft. long. In this he only imitated the practice of the earlier artillerists, who, having only slow-burning powder, which did not produce gases fast enough to induce very high pressure, wisely made their guns many more diameters long than we now make ours, which are designed for quick-burning powder. As examples of long guns I may refer to Queen Elizabeth's pocket pistol, the long Egyptian gun at the Horse Guards, and the Afghan matchlock-muskets, all of which were evidently designed for slow-burning powder, and to allow a large charge of it to be consumed before the expulsion of the shot, without which the range could be but short. The, to us, unusual proportions of all these guns clearly indicate to the scientific artillerist that theirdesigners well knew that the required velocity may be imparted to a projectile by the comparatively long-continued impulse of a force of low intensity, just as Perkins's steam-expelled bullets, with so high a velocity that the heat evolved when they struck against an iron target melted them. How long steam at 150lb. must continue to act on a 45 bore rifled barrel to expel a shot three to five times as long as its diameter, with the required velocity, is a mere matter for calculation or experiment. If Perkins's gun required a barrel 6ft. long to get up the required velocity in a spherical ball (as broad as it is long) with steam at 500 atmospheres, the length of barrel needed to enable steam at 150lb., less than 11 atmospheres, to expel a long rifle projectile which exposes much less surface to the steam pressure, and is about three times as heavy in proportion to its diameter, would seem to be something pretty considerable, not to say quite unportable-I think over 40ft. long. this is of no great importance; so long as you are killed, it would be quite unreasonable to grumble at the means provided by the forethought of a Moltke trust that the fearful efficiency of the means science or a Bessemer, with whose concluding hope and provides for the destruction of human life, may compel nations to "keep the peace," which the profession of Christianity seems quite unable to do; need I add that the performance of Christian morality would render war and, I may add, most other social evils which afflict human existence-simply impossible. THE HARMONIOUS BLACKSMITH. MANGANESE BATTERY-EMERY - RAILWAY ETC. mode of making and also with the points of excellence and after premising that "further description is un- since, so far as I can see, further description must be 46 an arrangement such as shown in sketch would rivet ammoniac? Perhaps it may be said, why not allow several shots to travel along the barrel at once? save us from the necessity of expelling one before This would another is allowed to enter, but if this be done, how about its action on the foremost shot? I should not like to say that 150lb. pressure could not be maintained behind it, but the pressure behind the next shot must be far greater if it be maintained, for that force would have to drive the second shot as fast as the first is moving, unless they actually touched each other, which, if allowed to enter successively, is impossible; there must be steam between them, and that steam would become expanded, and its pressure diminished, unless bullet, No. 2, travelled along the chase of the gun quite as fast as bullet No. 1. Thus every additional bullet in the barrel at the same time only adds to the difficulty, and we come back to that ordinary condition of success in most of the works of humanity-"one at a time." liable solution, will appear upon consideration of the The necessity for the above questions receiving a reHow to make long rifle projectiles, one at a time, enter number of questions asked respecting this kind of cell the barrel at the rate of 1,000 per minute, I feel compelled to leave to the ingenuity of a Bessemer. Should of "E. H. B." (534). Now this gentleman, desirous of in recent numbers of the MECHANIC, notably the case even he find it too difficult, I fear we must revert to the spreading popular science (a very laudable vocation), six-shooter, which, after all, would not require many wishes to obtain heat force with small resistance, and men to work it. Probably one man might guide two barrels, when used at short ranges, for (as the eleva- conductor, i.e., supposing the whole circuit to be cona similar force through a resistance of forty yards of tion would of course be previously obtained) only the tinuous for the twenty yards distance. Our great friend lateral movement of the barrels would be necessary. For in these matters," Sigma," appears to have been prelong ranges one barrel would be quite enough for one viously consulted upon this subject, but probably being man to manage; but, then, fewer shots would be required, so if three men were told off to serve a six- the subject of the "patent manganese," replied rather imbued with doubts somewhat akin to those I feel upon shooter they might be sufficient, besides the stoker and vaguely "that a large number of them would answer engineer might lend a hand in the good work. If a common road locomotive or a railway engine be emthe purpose of 'E. H. B.'" as we may say a large numployed to supply steam, one or two spare hands might would constitute a system, and a large number of such ber of planets revolving round a central luminary be carried, all hands when in action being efficiently systems may constitute the universe. protected from the enemy's musketry. To protect them from artillery fire without entrenchment would chosen (having tested all battery forms by a comparative In the first place then "Sigma of course be quite impossible, and as conld, had he so steam-engine affords a mark as big as a locomotive galvanometer), have said within one cell at least, how we must expect the enemy's great guns occasionally placed in excess, the cost would be small and success many would be required, and if the questionable one was bust our bilers" and scald us to death: but certain. a waggon, " [OCT. 28, 1870. definitively to "Sigma," I have not the slightest doubt but that gentleman would have courteously defined the Now, had "E. H. B." a second time put the question incomplete, and, in some parts, inexact outline, supposed to be a description of an induction coil for "large number" numerically. But, no! he flies from Sigma" to Dr. Coffin (who has, by chance, given an medical purposes), requesting cost, &c., of a thing which he confesses he has no knowledge of (a point wherein, no doubt, Dr. Coffin will deeply sympathize with him), and which, if he were acquainted with all the particulars he asks, unless he is an expert mechanic with plenty of tools at hand, and his time otherwise unduring the impending winter at least all his time to occupied (rarely the case with amateurs), would occupy make, and all next summer to try experiments to convince himself that his time had been thrown away. voltaic current, when other work is not done thereby," will, I have reason to believe, be fully given in a con"The laws relating to the calorific effects of the temporary, perhaps before this may appear in your pages; a short study of those laws will, no doubt, be of value to "E. H. B." (538.)-The experience of all brass finishers with washed or unwashed," either in planishing brass or legion) points to the one fact-"never whom I have been acquainted (and their name is grinding cock plugs, especially the latter operation, use emery the surfaces in contact for the time being, but enters, compared with best gun-metal, that it not only abrades for this simple reason that emery is so hard, even as or is forced by the mechanical operation of grinding, into the pores of the metal, from which it cannot again be eradicated after its normal work is done; no, there it remains, and every time the plug is turned abrasion goes on, until the plug or barrel of the tap is grooved and leakage ensues. A good sharp sand, or thoroughly calcined fire-clay, finely powdered, will answer the pur pose more rapidly than emery, without incurring this objectionable result. is-who grinds the plugs and how? Need I add that the chief point the curiosity to investigate as to whether the wheels were fixed or revolved on the axle; in fact, on such a (539.)-I have seen the Brixton tramway, but had not rond I think it almost a matter of indifference which plan is adopted. has been mooted and discussed almost ever since railBut with regard to railways the matter assumes a very different phase. The question went so far as to adopt the principle of loose wheels; ways have had an existence for passenger traffic, and I have not access just now one company of our Transatlantic brethren, I believe, thrown down a precipice-the results in loss of life and the innovation in full bloom, ran off the line, and was to the details, but, if memory serves me correctly, the first train started with limited number of incipient engineers, troubled every suggestion of another trial, except amongst a very damage to property being such as to prohibit even the venture to hint that our friend," F. S. Ekciwnuh," has not yet arrived even at that initial point in the science now and then with the cacoethes scribendi. which must be known before he can hope to become May I compelled to move in a curvilinear line would, if suddenly set free, move off at a tangent to such curve, an engineer, or he must have known that a body and not, as his carefully-constructed diagram (so far as the paving stones are concerned) shows, move in a curve of smaller radius? usually acknowledged, and generally understood by both have their uses, but have also their causes, and There is a slight difference, engineers, between centrifugal and centripetal force; gineering. it is necessary to distinguish between them in en round which a fresh discussion of the "original intion of Mr. G. R. Luff is not intended as a nucleus (544.) It is to be hoped, sir, that the communicaSurely, enough was said and written before the paltry ventor of the screw propeller" is to be inaugurated. subsidy was wrenched from the hands of Government and distributed amongst the many claimants, to render a re-opening of the matter not only unneces sary but offensive! The one who got the lion's share still lives, and long may he live to enjoy it will, I Bishop Heber and the King of Oude are, I believe, believe, be the heartfelt wish of all who waded through things of the past who will not, at least in this life, the evidence that placed the laurel on his head! succeed in tearing the well-earned honours from the brow on which they rest. 66 Passing on to 547, I must confess it makes my very know, amongst the most virulent opponents of this justification of the bicycle. Who, I should like to teeth water to have a chat with "Griffin," upon his five miles an hour without greater fatigue than he could "fad of the hours walk the same at three or four miles per hour, he has would presume to argue that if a velocipedist can do a long journey at six or even decidedly gained"? Why this is almost axiomatic; but in the language (p. 78) of our good friend the real point of a subject, at once its chief difficulty, and the key to its mastery is avoided." Mr. Proctor, I am "struck with the skill with which system as a whole is about as good a means of formance of work so far as resultant feelings are conmeasuring the amount of force expended in the perThe human cerned, as it is, compared with a thermometer, a measurer of heat. the worst instrument that can be consulted, and the who has performed his wondrous feats in a minimum of time, and, of course, felt no fatigue; but this is no standard at all. I have seen a man raise the whole weight of his body through the greater portion of his height in a very short time, without making any apparent progression, by turning twenty-five consecutive somersaults, but he did not come before the audience and say, "Gentlemen and ladies, you see what I have done, and I can assure you I can do the same thing for four or five (I put the number moderately) hours continuously, and without feeling the least fatigue !" The mountebank feels too well what he has accomplished, and what it has cost him to do it; and if any aspiring genius to the profession were to ask him immediately after his effort how he (A. G.) could acquire the faculty for imitating or even excelling in this wondrous art, he would receive Punch's advice to those about to marry, "Don't." (553.)-I do not know" Dyer," nor am I acquainted with Mr. S. T. Preston, but methinks before the latter finds fault with "Dyer's" instructions he should at least make himself acquainted with the principles upon which from his own showing they are based. If by Dyer's book "Mr. Preston means the shilling treatise published by some enterprising mathematical instrument maker in London, I beg to inform Mr. P. that the pasteboard tube is not the principal insulation in the coil therein described, but is simply the cheapest and best method of doing what "Dyer" sets out to teach people to do, who from necessity are obliged to work upon a small scale. If, as Mr. P. states, hardly any insulation is necessary between the primary and fasciculum, let him try one of the worst conducting metals, say lead, and use a tube of this material instead of a pasteboard one, and favour us with the resulting advantages from decreased insulation in this particular. Then let him try iron, brass, and copper on the one hand, reducing the insulation at each step, and in the opposite direction substitute tubes of glass, gutta-percha, india-rubber, and finally ebonite, and cæteris paribus he will soon find from his results that insulation must not only be used where "Dyer' places it, but that the better it is the better the results obtained. That better insulation is desirable between the primary and secondary coils all will admit, and almost every volume of the MECHANIC bears testimony that all who have written upon it have insisted upon this point as a sine qua non, but the fact of its necessity there does not for a moment prove that it is unnecessary in another part of the machine. The only thing we do know (obtained from tentative processes) is, that no part of a circuit, whether primary or derived, can be too well insulated by the means we have at com mand. When the new theory of electrical science, foreshadowed in the papers already given by "Sigma," shall have become established as an incontrovertible fact, it will be quite time enough for Mr. P. to point out" radical faults" which in our present state of knowledge seem to be not only admissible, but absolutely necessary to exist. I must apologize to you, sir, for the inordinate length of this letter, for I had no idea when starting that it would require so many words to put a few facts in a clear light, and it has been anything but pleasant to me to continue a series throughout as a "grumbler" rather than an adviser, even if not rising to the dignity of a teacher. Yet one point is gained-I have, if you print me, shown where broad assertions must be taken cum grano salis, and thus, I trust, induced the spirit, which while it "tries all things, holds fast to that which is good" in this communication, constituting my personality a shielding beacon on the rocky shores of the Scilly Islands; but I cannot yet conclude without a sincere hope that the query (5109) being the first, will also prove the last "canard" that will reach you as a consequence of the "halfpenny post-card" arrangement, a thing in itself a boon to thousands, nay, tens of thousands, but like all other good things, leaving a mischievous loophole for vicious and unprincipled barbarians to grin through. WM. TONKES. the table. picture requires two of the silly birds which saved the Capitol, and when tired of them you can't get rid of them, for alas, although "geese," as they are not the right form for his purpose, your tailor won't take them off your hands, in part payment of his overdue account, when you are tired of spoiling your pictures with them. However, it is some comfort that these geese, like the steam engine, eat nothing but coal, and don't require to be fattened, but only heated for First-rate restoring is far more costly than lining, but I have seen it done by amateurs who had a good eye for colour, and knew how to handle a fine fitch pencil, quite as well as by first-rate professionals. It is a matter requiring time and patience rather than artistic skill, and it has been said (I think untruly) that a good painter must be a bad restorer. Certainly he is rather apt to restore a picture until it looks remarkably like one of his own paintings, but in this respect the professional restorer-who don't profess to be anything else than a restorer-is often quite as bad as the painter. Contrary to the rule of the housepainter, who charges you in proportion to the colour he uses, the true restorer's rule is "short measure high price." The less paint he uses the more money you have to pay; but then it is some consolation to know that, c. p., the less paint the more perfect the restoration, a word which is not exactly synonymous with painting a new picture of the same subject over the old one, although this too is often done. THE HARMONIOUS BLACKSMITH. = A DESCRIPTION OF THE STRASBURG CATHEDRAL CLOCKS. [662] SIR,-With your permission I will, in this letter, content myself by giving a description of the two ancient clocks, and reserve the description of the present one for another communication, as I find to describe the whole in one letter would take up more of your space than I am sure you would or could allot for this purpose. The first clock was begun in 1852 and completed in 1854. The case, which was of wood, consisted of a calendar like those in use at that period, representing in a painting some indications relative to the principal movable feasts. By the side of this calendar, formed of a large disc of wood, there was hung a picture, upon which were in German rhymes a description of the wondrous properties which our credulous ancestors attributed to the seven planets. In the middle part there was an astrolabe, whose hands showed the movements of the sun and moon, and also denoted the hours of the day, minutes, seconds, &c. There was placed at the same elevation the movement proper of the clock. In the upper part was a statuette of the Virgin Mary, before which at noon the three Magi (Wise Men of the East) bowed themselves. An automaton cock, placed at the top of the case, crowed at the same moment, moving its beak and flapped its wings. A small set of chimes composed of several cymbals, also formed a part of this clock. The second clock was commenced in 1547, its authors were Dr. Michael Heer, Nicholas Bruckner, and the celebrated Professor Christian Herlin, with whom were associated several intelligent artists and workmen. The death of some of these and the troubles of the period caused the work to be delayed, and it remained suspended until 1570, when it was recommenced by Conrad Dasypodius, a discipline of Herlin, by whom it was constructed upon a larger scale than was originally intended. He had the assistance of several distinguished professors, amongst whom was the celebrated mathematician, Oswald Schrekenbeaufuchs. The mechanical part was made by Isaac and Josiah Habrecht, who had already become known as astronomical clockmakers. Tobias Stimmer was employed to do the paintings and the sculptures. At the foot of the clock there was a celestial globe, supported on four richly carved columns. It performed a revolution on its axis, showing the stars known to Ptolemy, in number 1,020, grouped in forty-eight constellations. Two circles, one earrying the sun, and the other the moon, revolved A FEW WORDS ON PICTURE LINING AND round the globe. Behind the globe was a large wooden RESTORING. [661] SIR,-"F.R.C.S.," No. 5060, p. 71, requests to be informed how to line pictures. Having had some experience thereof, perhaps he will excuse me for giving him a little bit of "advice gratis" on this subject, which advice is comprised in the one word "Don't." If his pictures are bad they are not worth spending money on; if, as I hope, good, they are well worth the comparatively small cost of lining by a professional, and not being spoiled, which is the very thing an inexperienced person would be likely to do. Picture lining is done for a very moderate cost if, instead of sending them to a fashionable West-end dealer (N. B. even they are not all exorbitant), you have them done by a regular liner (I do not mean a passenger ship) who charges you the same price as he charges the dealer. In proof of this I may state that the very first oil painting I ever bought (many years ago; my taste for collection is no new thing-our follies stick to us), its subject is the Wise Men's Offerings, said to be by Old Franks, size 38 x 29 = a Kit Cat, only cost me ten shillings for lining, and it was done as well as any picture I ever saw-not with a wretched calico back, but good white canvas. Now I think "F.R.C.S." (who must know that good surgery is the cheapest, whether pictures or humans are the subjects) will see that it is better economy to have the work done by a skilful and careful operation than to purchase a set of "instruments," including a heavy ndigestible "goose" weighing at least 281b. A large disc, on which was painted a calendar, which made a revolution every year. Statues of Apollo and Diana, placed at the sides of the disc, pointed to the dates. The central part of the calendar contained a plan of the city of Strasburg, a list of towns on the Rhine, and the names of the persons who had been employed upon the clock. In compartments at each side of the calendar were two large pictures, upon which were painted all the principal eclipses of the sun and moon for an interval of thirty-two years. These were intended to be renewed each thirty-two years. Above the calendar were placed the seven Pagan divinities that have given their names to planets, and to the days of the week. These allegorical figures, seated in chariots, drawn by the divers animals which mythology assigns to them, showed themselves successively on the days which were sacred to them. On Sunday Apollo was seen, this day being dedicated to the sun. The ancients named it dies solis (the day of the sun), and the Christians (dies Dominica). Diana showed herself on the second day, which was called dies Luna (day of the Moon) Lundi, Monday; and so on during the week. Immediately above these divinities was a gallery, the middle occupied by a small dial, which indicated the minutes and the quarter hours. At the sides of the dial were seated two genii; the one on the right raised a sceptre, and the one on the left reversed an hour-glass every hour. An astrolabe, constructed according to Ptolomy's system, occupied the centre, in the interior of which was contained the wheelwork of the clock. Six the Lord's Day pointers, bearing each a planet pointed, upon twenty. four divisions of the astronomical day, the movements of these heavenly bodies; one pointer, larger than the rest, and bearing the sun, made every twenty-four hours a revolution round a map of the world, placed in the centre of a large dial, which was also ornamented by the circles of a horoscope and the twelve signs of the Zodiac. The upper part of the astrolabe showed the phases of the moon, which was represented by a gilded disc, whose movements exactly represented the periods of new and full moon, &c. At the third story of the clock, upon a platform, stood four statues representing the four ages of life. These figures struck the quarter hours upon cymbals; above these was the bell for the hours, two figures stood beside it; the one, Death, represented by a skeleton; the other, Christ bearing a cross and a palm branch. At the instant the hour ought to be struck the Saviour came forward and the skeleton drew back; but immediately Christ retreated precipitately, and Death advanced to strike on the bell. This movement was repeated each hour, as many times us there were strokes in the hour. On the summit of a turret, placed on the left hand, was perched a cock, which crowed first daily at noon, flapping its wings and opening its beak, but having been struck with lightning in 1640, it from that time ceased to crow, except upon Sundays and feast days, until 1789, when it ceased crowing entirely. This clock, which represented the state of horological knowledge of the sixteenth century, was, for the period, a real masterpiece; hence it was considered one of the seven wonders of Germany, of which Strasburg then formed a portion. The most eminent poets of the time vied with each other in making it the subject of their songs. An inscription, of which the following is a translation, was formerly to be read over the great entrance gate of the Church of Mayence: The seven wonders of Germany are-1, the Tower of Strasburg; 2, the Choir of Cologne; 3, the Clock of Strasburg; 4, the Organ of Ulm; 5, the Fairs of Frankfort; 6, the Mechanism of Nuremberg; 7, the Guildhall of Augsburg. THOMAS ARMSTRONG. THE SIZE OF THE IGUANODON. [668] SIR, Mr. Underhill (page 101) is mistaken when he says that "specimens of the Iguanodon have been found 50ft. long." No specimen of an Iguanodon has been found at all; but teeth and fragments have been found. I have at this time in my possession upwards of 100 vertebræ, from Potton, Bedford, forming part of the greatest find of Iguanodon bones that has ever been known. Now in 1841, when Professor Owen, at the request of the British Association for the Advancement of Science, drew up an elaborate report embodying the result of his own researches, and those of other investigators in this field of Paleontological inquiry, the largest Iguanodon vertebra known was rather more than 4in. in length-that is, taking the measurement through the centrum of the vertebra in the long axis of the body of the animal. As it is highly probable that the number of vertebræ in the neck and body was about 24, if 14ft. be allowed for the sacrum, and something for the vertebral interspaces, this would give about 10ft. for the length of the body. Then allowing 3ft. for the head, and 13ft. for the tail, we arrive at a total length of 26ft. to 28ft., or about the length of the largest known of the living crocodiles. These dimensions, however, have reference simply to length. In bulk, the Iguanodon was truly a giant. Respecting the great find at Potton, I may have something to say in your next number. EDWARD CHARLESWORTH. FEED-WATER HEATERS. [664] SIR,-Mr. Baskerville's conclusions respecting the economy of feed-water heaters (1. 359, page 610) are undoubtedly in the main correct, but some of his arguments in support of them appear to me unnecessarily obscure and equivocal. It was for this reason that I addressed a query to him on the subject, to which, as yet, he has not thought fit to reply. In the first place he gives the temperature of steam at 55lb. pressure as 1,200, while the tables of Messrs. Arago, Dulong, and Regnault, quoted in Fownes's "Chemistry," call it about 294°. Then as steam is capable of heating to 212, 56 times its own bulk of water, the saving effected by a good feed-water heater ought theoretically to be only 17-857 per cent. for 56: 1 :: 100: 17·857. If it were possible to utilize the whole of the waste heat of the exhaust steam, this estimate might, of course, be largely exceeded, but since 212 is the highest temperature that can be communicated to water in an open vessel, this is out of the question. I hope Mr. Baskerville will take these remarks in the spirit in which they are intended, not as an attack upon him or his valuable paper, but simply as a seeking after VERTUMNUS. truth. THE MUSIC OF THE CRICKET. [665] SIR,-If the "wing" of any of the orthopterous insects be examined carefully by the aid of a sufficiently high power, there will be seen a space, scarcely crossed by veins, but bounded by a large dark vein with three or four longitudinal ridges. In front of this is a transverse horny ridge furnished with numerous teeth. Naturalists now are, I think, commonly agreed in regarding these as the means by which the music of the cricket and other orthoptera is produced. The two "files" or bows are most probably sharply rubbed against each other, and the " "tympanum or "drum," HARMONIUM CONSTRUCTION. the veinless space of which we have spoken, acting as a sounding board, gives volume to the sound thereby produced. Our" cricket on the hearth is capable of enliven ing the solitude of our English houses, but it is far distanced by the musical cricket of the Amazons, (Chlorocelus Tanana), an insect ranking between the crickets and the grasshoppers. The musical apparatus of the latter differs from that of the cricket in so far that the "bow" is on the hinder thighs, and the action of these upon the wing-cases produces the shrill sound so well known. As for the motive of the creature in producing the sound, we may safely regard it as a love song, the homologue of the melody of the bird, or the "verse" of the juvenile biped homo. [666] SIR," Robinson Crusoe," letter No. 623, is, I believe from my own observation, quite right about the grasshopper. I caught one and made him sing when I liked, by working his hind leg, and obliging the inside of his thigh to rub against his rough side or edge of wing, might be, if he has any. This was years ago, and I have till this week never seen the chirp explained so in print. I don't like to touch crickets, ever since I read Dickens's one "on the hearth" not that I am sentimental. HARMONIUM CONSTRUCTION. the key of G, the second rod will sharpen all the C or key D two sharps, and so on with the others. The same is done for flats, only it is the rods on the left hand moved to the left. In all these cases the white keys alone are used, the black are only used when an accidental sharp or flat occurs in the course of the tune. In connection with the above, music may also still, more be simplified by writing it in the following style a modification of the Sol-fa notation: Air. AG This is the first measure of the Old Hundredth as an example; the letters are the names of the notes on the keyboard, and the bars show the duration of each note; each part has its own column. I am well aware that these helps will be of F little value to professionals, or those who have mastered the difficulties of the science, yet if you think them worth a place in your columns they may be of use to some one who would like to play a common tune with little trouble, for all H. P. A E A C 22 conjunction with pipes. And I repeat it in other terms, which I hope "H. B." will be able to understand this time, when it is necessary to reinforce a note by a column similar to that of an ordinary pipe it is absolutely necessary that the dimensions of the pipe should have a perfect identity with the note to be reinforced. Strictly hen a 16ft. note requires a 16ft. pipe. The exceptions named by "H. B." are merely exceptions. No doubt a pipe one quarter, or even one-eighth of the valne would vibrate in unison with some of the harmonies of the fundamental note, but my formula is strictly in accordance with the law regulating the sonorous body, and even Day felt the necessity imposed on him by the law, although he has not formulated it very explicitly, when he says in reference to his boxes, "the size of the box must be proportionate to the tone to be produced, it requires to be increased in size as the tones become graver." I believe the subject upon which "H. B." wants gently to draw us on is the communication of the vibrating movement from the sonorous body to other solid bodies surrounding it. This is an unexplored subject, and less is known upon it in relation to the harmonium and its case than in relation to stringed instruments, such as the violin, the violoncello, the contrebasso, and the piano. Modern manufacture has abandoned the seeming advantages which appeared to be offered in the old patents of Day, &c., for other methods offering results equally as good without the extra demands on space, weight, and cost necessitated by their complicated system. For the harmonium maker there may be still much to learn, but I believe that to retrogade to the old patents for placing the reeds on very empirically constructed boxes would not be a scientific procedure. It is no more scientific to combine them with pipes, unless those pipes are of sufficient size to vibrate simultaneously with the vibrations caused by the note of the reed. The space required, however, in either case would place the harmonium in a different category amongst instruments than it now occupies, and the study of the subject pertains more to the role of the organ builder, where the combination of reeds with pipes has already been attempted; whether successfully or no I cannot say, but our friend "H. B." seems to know from his experience of the manner in which temperature affects the one and the other. Respecting harmonium construction, the law which demands the attention of makers is that which affects the communication of the sounds or vibrations of the reeds to the channels, the pan, and the case, or, generally speaking, to the solid matter which surrounds the sonorous body. Savart compares the mass of air in such an irregular space to "that in a large organ-pipe, where the sonorous waves by their ebb, their flow, and their clashing, form bellies and knots of vibrations whose positions vary infinitely according to the form and dimensions of the interior of such space and the articles contained in it." When manufacturers shall have sufficiently studied the laws affecting the surroundings of the reeds, so to speak, instead of wasting their time upon mechanical combinations more or less felicitous, no doubt they will obtain good results. This instrument, inferior perhaps in quality of sound to the piano, nevertheless so rich in resources, "would have very soon dethroned its rival, if makers, by an intelligent application of the laws of resonance and the communication of the vibratory movement, could have conquered for it that roundness and purity of tone which distinguish stringed instruments, and in place of complicating the study by insignificant attempts which do but reveal its imperfectness, they would confine themselves to the task of perfecting its variety of tone and sound." I quit this subject for the present, and in conclusion I would ask your correspondent, E. H. Jones, to give us his experience concerning the exhaust bellows of the American organ. There is something highly captivating in the idea that the sounds are produced by the exhaustion of air, and should Mr. Hinton Jones fail to favour us with an explanation, would some of your other scientific correspondents (Mr. Hermann Smith notably) ventilate the question, seeing he has left me a long time without a reply? MARK ELLOR. DOMESTIC ORGANS. [669] SIR,-I think the one fault alluded to by "J. D." in his letter, 568, "the scales, &c.," may easily be got over, after settling the pressure of wind, as the voicing will reduce a pipe of large scale to the I have one required tone for a chamber organ. VALVE. [668] SIR,-It would be a great pity if our discus. sion of "Harmonions Blacksmith's" (564) proposition (not to call it hobby) should turn out to be merely a discussion of names and terms. If he intends me to fall into the snare of calling a box or a channel in harmonium construction by the name of a pipe I shall [667] SIR,-I send you a sketch of a modification of the harmonium, by means of which I think the playing of the instrument may be much easier learned, that is to be learned is the name of the notes on the keyboard. especially by those who have neglected this branch of education in their youth. It is intended to do away with the sharps and flats at the beginning of a tune or the signature of the key (which must be a very great hindrance to young beginners), and to play upon the white keys alone for every key the same as key C. The annexed sketch is a section of the harmonium. A is the bellows, B the well, C the pan, D the swell box, E the pallet levers, F the keys, G the sticker. Upon the sticker is fixed a small arm r, about 1 in. long, which depresses the pallet lever when the key is pressed down. o is a small spiral spring for keeping the sticker up. There is a jin. knee formed on the bottom of the sticker, which passes through a slot in the lever a; these levers are all connected in octaves of the same name by a slender rod e, so that when one is moved the others move also. There are seven rods f, which project in front of the instrument, which are attached to these rods (one for each note in the scale), and moves them to the right or the left, and consequently moves the arm on the sticker to the pallet lever above for a sharp, or the one below for a flat. Suppose a une is one sharp, the first rod on the right hand is moved to the right, and that will sharpen all the Fs on A. F. which I planned and made part of, suited for a moderate-sized room, consisting of one manual with Lieblich Gedact, principal, and 15th through to C C; Gamba, grooved into Lieblich below tenor C, and flute to C, enclosed in a swell box; open diapason in front F F to Gs, divided at' middle C in order to obtain a certain amount of effect for solo playing. Twentythree pipes of spotted metal make a handsome front carefully avoid the temptation. The laws of the vibra- and keep the mechanism from sight; height, 8ft. 6in. ; tions of air in pipes whose diameter varies from one-width, 6ft. 4in.; depth, 3ft. 3in.; including case. fifth to one-twelfth of their length are well known, but those laws when operating in irregularly constructed chambers have not been sufficiently studied, and no formulæ exist explaining them. Contrary to his expressed opinion, "we can come to some agreement regarding those proportions of length to breadth which shall separate pipes from other resonant air-chambers," and I think we shall not err in keeping in view the proportions of an organ pipe when speaking of pipes in a musical sense. The laws of their vibrations being, as I said, well known, the rule which I laid down in my last (506), though subject to the exceptions which are always implied in any general rule, is, nevertheless, strictly the rule to be observed in laying down reeds in [670] SIR,-I now send drawings of the small "Domestic Organ," and the cost of the material required to construct one. As will be seen, the principal peculiarity about it is a very compact bellows, which, although powerful, takes only 9in. in height; the twelve largest of the stop diapason pipes are planted off the soundboard down at the side of the bellows, six on each side, and wind conveyed to them by conveyance tubes, and if the principal is carried through in metal, the same number must also be planted off in a similar manner. No. 1 is a front view of the interior of the instru ment; No. 2 a sectional view; the letters refer to the same parts in both. A, is the keyboard; B, stickers; C, wind-chest; D, bellows. The keys are like harmonium keys, hung at the back, and beneath them is a lever, working in similar way, but with the ends the reverse way of the keys; the key presses on this lever by a screw-pin, by which means the key is levelled; the sticker is attached to the lever, having a wire at the other end, which goes through the soundboard and pushes the pallet open. UNEQUAL STEAM PRESSURE. [672] SIR,-In some of the former numbers I sent you diagrams taken from our engine under the above head, and I feel greatly obliged to your correspondents, Mr. Wood and Mr. Malbon, for the information I gained from their controversy in your valuable paper. We have since then put in a new boiler, and raised our steam from 351b. to 70lb. pressure per square inch. We put in. of lap on the high-pressure cylinder, and shortened the rod between the valves fin. The valves The cost of making such an instrument will be about of the low-pressure cylinder we left as they were, and put the excentric forward about in. on the shaft. I now enclose you diagrams taken after these alterations as follows: Open diapason to mid C, unvoiced £1 10 0 Set of keys Four stop knobs, engraved Four skins of half-strained leather THERMO-BAROMETER. [674] SIR, -The instrument sketched by "Junius" (596) is in principle identical with Adie's sympicsometer, which is made of various sizes. I had one a few years since which might be in one's pocket without one's knowing it. I consider it far inferior to a good aneroid, and a fortiori to a good mercurial barometer. I will send sketch and detailed description if desired. G. J. SYMONS. SATURN IN DAYLIGHT. [675] SIR,-If "F.R.A.S." refers to my last week's communication, he will see the object-glass is 2țin., not 2 in. I should not have been surprised had I been using an astronomical eyepiece of only two glasses, but to have seen Saturn and his rings distinctly as I saw the craters in the moon in broad daylight with such an object-glass and day power, was, I thought, worth recording. AMATEUR. WATCH JEWELLING-LEVER ESCAPEMENT. of last vol., through some inadvertance I used the words [676] SIR,-In my answer to query 4128, p. 428, "slide-rest," had I written "T rest," I should have been better understood. The tool in question is called a balance tool, it costs from 12s. to 15s., and is used for turning such pieces as cannot be conveniently placed on an arbor. I reproduce it, showing a few of the chucks that may be fitted to it. A is a screw-head chuck for filing up and polishing screw-heads, about half a dozen of these are usually made for the different 11 10 0 If the principal is only carried down to tenor C in metal, the price is £1 17s. 6d., instead of £4 10s., then the lower octave would be stopped wood, and would not require planting off the soundboard. I have not taken into account the price of the case, as any sum may be spent over it according to taste. I have given the price of "unvoiced" metal pipes; to get them voiced will cost about 10s. per stop more. A great mystery is generally made about voicing, yet very few parts of organ work are easier to do, and by attending to the following directions, any one can do it; the tools required are, a small three-sided nicking tool, to make the teeth in the block or "language" of the pipe, and a penknife to cut the mouth. If a smooth tone is required the teeth must be very fine and close together, the quality of the stop is obtained by the width or height of the mouth, the rule being that for sweet, round, smooth tone, the mouth shall be small for the size of the pipe, and the supply of wind moderate, little more than half what the pipe will take without being over-blown; if a bright smooth tone is required, give as much wind as the pipe can take without overblowing; if a sharp reedy tone is required cut the mouth considerably "higher" and increase the wind in proportion. As an illustration take the stops dulciana and German gamba; the pipes are precisely alike in shape and size, but the mouth of the gamba is half as wide again as the dulciana, and it takes twice as much wind; the supply of wind is regulated by enlarg. ing or diminishing the aperture at the foot of the pipe. THE PIANOFORTE. J.D. HO taps. B is the shellacing platform, used for purposes innumerable-to turn or hollow out anything, for jewelling, &c. C is a chuck, with a hollow centre for turning anything that has an arbor; a fuzee may be waxed on to turn or polish the pivot, when the arbor for the purpose is not at hand. If "Rupert" imagines he has a foot hole waxed on the chuck represented in the tool, and that having warmed the chuck, just as it is, with the flame of a spirit lamp, he takes quickly a piece of peg-wood pointed like a small screw-driver, with the flat edge cut a little slanting; if he puts the pointed corner to the hole of the jewel, to centre it, bringing the flat edge gradually to the surface of the stone, to make it run true in flat, he will find, with a little practice, it can be done in two or three strokes of the bow. This is how everything is waxed on to the tool; the pieces that have no hole are centred by the outside circumference, using as little sealing-wax or shellac as possible. 66 were made, and should feel obliged if some of your Rupert" will see the work is quite under control. How easy it is to turn anything in this way. Pieces that are larger than this tool will take, can be done on a mandrel; a Swiss mandrel is the most convenient, as the a hundredth of an inch in any direction, thus not requiring such steadiness of hand as the English mandrel. There are some English mandrels that have slide [671] SIR,-I send you a piano suggestion, hoping the steam on to the piston at a greater pressure when cutter is fixed in a slide-rest, and can be moved within it may be of some use to my fellow musical readers. There are two pedals on a pianoforte; why not add a third (as I have done) to make it piano and forte at the same time? The means whereby this can be done will be very apparent to any one who knows how a pedal on the piano acts. By the addition of this third pedal the Can any of your readers tell me whether it would be usually the case in foreign work; for if it were not so treble is made to stand out with brilliance, while the bass gives out a subdued forte. I have not thought it needful to give a further explanation, unless the idea be approved of. CARL DITTENHOFFER. possible to exhaust our steam from the engine into it INQUIRER. A jewel can be set in an old setting, and this is the whole of the old setting would have to be cut out, thereby making an enormous hole, which would be neither convenient, nor in most cases, practicable. At all events, a jewel must be found exactly the same size |