what would now be termed, in music-hall phraseology, "a lady vocalist," i.e. Miss Brinkley, as early as 1767. He might as well also have stated that the elder Dibdin was the accompanist in this first recorded public use of the pianoforte. The instrument he used might have been a pianoforte proper-which, it having been announced by that name, it probably was-or it may have been a hammer harpsichord of English or German manufacture. There is no impossibility in its being English, for we have home-made pianos a year older, not to mention that the "apostles" might then have been hard at work converting the musically-barbarous natives of England from the idolatry of harpsichordism to orthodox "pianoforteism," with a success rivalling that of the South African bishop, whose missionary labours among that little known native tribe of African idolators, who rejoice, or ought to rejoice, in the euphonious name of Kanoodoodoodooldums, were, in both senses of the word; so very "graphically illustrated" by the clever author of the celebrated Bab Ballads. N.B. He wrote this veracious (for as the noble author of "Zanoni" would have put it, he presents to us the real, if not the actual) history of that bishop's Christianlike doings, in the way of reconciling religious differences, in a most earnest and truly Christian spirit, although truth compels me to confess he only did it in "Fun." I feel tempted (only just for once) to digress, and say a few words about Dibdin. This musical genius, who built the Circus, now the Surrey Theatre, another theatre in Beaufort-buildings, which he named the Sans Soucy, and yet another which he called by the same title-now, I believe, the auction rooms of Messrs. Bonhams, in Leicester-place, from whence I have abstracted (after paying for it) many a pleasing picture, not to mention "certeynge and sundrie" pianofortes and other musical instruments. Dibdin, was, I believe, the first Englishman who gave musical entertainments unassisted. For some of these he composed his cele-, brated nautical songs, one of which asserts that a sweet (well, he might be sweet, all things considered) -little cherub sits up aloft, for the humane purpose of "looking out" for the life of poor Jack. How he, with his peculiar conformation (which however much it might conduce to sweetness, and if not light itself, certainly lightness, as every Christian is so posteriorily constituted as to require the assistance of Baxter's celebrated back "shove" can testify) could sit, is just one of the many things no fellar can understand. Dibdin's sea songs were extreemly popular in their day, and had the credit of greatly assisting to man the navy. I should be inclined to suspect that with all our Jack Tars' patriotism (often accompanied by a strong desire for prize-money), that constitutional safeguard-yclept the pressgang-now, I am very sorry to say, a thing of the past, for Conservatives to regret had just a leetle to do with this matter. But then John Bull has long worshipped shams; why should he not worship musical shams as well as others? Dibdin was accustomed to accompany his songs by a very complex musical instrument of his own design a sort of organized piano-which I believe had pipes, drums, bells, triangles, and other sources of harmony (query of noise and dissonance), which my own father -who knew him personally, and often "sat under him," I mean attended his performances-told me was very effective indeed. Now I have heard several similar instruments of English and foreign make, and, in a certain sense, I have no doubt whatever it was like them, very effective. The poet says or sings, 'Tis distance lends enchantment, certainly quite as true of the whole generation of such " stunners," as it is of any view, earthly or celestial, within the power of our telescopes. Nevertheless, I should be very glad to know what has become of it, and see it added to that collection of queer old odd fiddles and other things in the Museum, which Punch's polite juvenile miss very improperly termed funny, to the horror of her governess, who very properly told her never again to use so shocking a word in public, most especially not in the sacred precincts of South Kensington Museum; for said she, "Government objects to such a term being used to describe works of art. My dear, you ougi o say 'curious' or very remarkable,' and neve o use so vulgar a word as funny." Itrust, if Dibdin's instrument is yet in existence, its present owner will either present it to the nation or sell it for a valuable c-o-n-s-i-d-e-r-a-t-i-o-n. power of mine, which is the only instrument deserving the title of "consort" harpsichord I have had the pleasure to hear; but as a description of it is published in No. 275 of the ENGLISH MECHANIC, I, as usual, eschew vain repetitions. It is quite certain the piano did not come into general use as a solo instrument in the concert-room until the masterly playing of Musio Clementi was heard, and "took the town by storm." Not only was Clementi a very "stronghand" on the harpsichord, but, for his time, a very great pianist. Some of his compositions are far from easy. The great Thalberg, at the Exhibition of 1851, told your very practical correspondent "W. T." that, excepting his own compositions, he seldom or ever practised anything but "Clementi's Gradus ad Parnassum," a work I strongly recommend to the whole generation of young lady players, it being a collection of remarkably "easy" exercises. When they have mastered them, they need little fear anything else within the reach of their fingers. Indeed, if young ladies' hands could command twelfths, I fear we should not greatly admire them I mean the hands, not the twelfths-any more than we admire big female feet; for, be it known to all men and women, that the female foot should not quite equal the Queen's foot-I mean the third part of her standard yard-or twelve inches imperial measure. Our pianoforte historian seems strangely misled by his reading. "How readest thou," is a question I think it would sometimes puzzle him to answer. He says that very ingenious mechanician, Merlin, tried in 1774 to effect a compromise between the harpsichord and piano (by combining both), which had then nearly superseded the former. The patent of Merlin lies before me, and I can find no trace of any attempt at compromise in it. Merlin simply proposes to do, by better means, what had been done on the Continent, and probably in England also, at least half a century before his time-viz., to put hammers to harpsichords in addition to its jacks. That he afterwards constructed three unison grand pianos, with jacks added, is nothing to the purpose. Robert Stodart did it soon after; and so far from this indicating that the piano had superseded the harpsichord, it rather indicates that the harpsichord yet maintained the lead, or at least, yet had so much influence that the pianoforte-makers thought their instruments could not stand alone. So far from the piano having generally superseded the harpsichord at this time, it is likely that if the books of Tschudi, Broadwood, & Co., and Kirkman & Co., were obtainable, they would show more than a score of harpsichords made for one grand piano; and probably if we had similar returns of all the small pianofortes and spinets, the latter would show a very large majority, although perhaps not so large as the preponderance of the number of harpsichords over grands. Probably Robert Stodart never made a harpsichord proper in his life; but even he, by the invention of a check inserted into the key, remedied the chief defect of Christofali's action-viz., the long drop of the hammer into its cuneiform rest after the hopper had been "set-off," by means of this check, probably gave the grand pianoforte the greatest impetus towards its adoption for use in the concert-room it ever received; for from Stodart's time until the so-called double action of Sebastian Erard was invented but little further improvement was made in the mechanism of this instrument. Indeed, but little more was required to make it as perfect as any mechanism could be, in which the hopper is made to escape from beneath the shoulder of the hammer butt. Erard first showed us how to do this, and yet to retain the capability of repetition, formerly confined to single actions without checks; but like most inventors-I plead quite as guilty myself of committing this fault as any one who has attempted to improve pianofore actions can do-he first did it in a very complex, however efficient manner. From the sin of complexity, that firm are yet far from free. With all the consideration due to commercial requirements, and making every allowance for the very natural independent feeling which renders first-class firms unwilling to adopt the improvements of small makers, however excellent their designs may be, I have often wondered that Messrs. Erard have not adopted Stumpf's modification of the principle of their own action, which I find does its work in my experimental grand piano equally well, if not better; i.e. it enables the player to repeat the blow with the key equally low, or even lower than can be done with the mechanism used by Messrs. Erard-for I can do it with certainty, by allowing the key to rise rather less than the sixteenth part of an inch, the hammer being effectually checked between each blow, however rapid the repetition. Surely it would be no dishonour to Messrs. Erard to adopt what is only a simpler and improved method of carrying out the principle of the invention of the talented founder of the firm, especially when it is considered, that by doing it, the action is so greatly simplified that the number of centres of motion is reduced from six to two, irrespective of that of the damper. Through error we arrive at truth, and through complexity we-in mechanical designs and constructions-arrive at simplicity. That the pianoforte superseded the harpsichord in the theatrical orchestra at a very early period is an obvious mistake. I must doubt - although often employed to accompany the voice, when it was wheeled on to the stage when needed-that it did so generally until about seventy years ago, perhaps not so soon; for until about 1810 it was so weak in tone that the harpsichord continued to surpass it in power. One of the most powerful harpsichords ever constructed was burned in the fire which destroyed old Covent Garden Theatre; but whether another succeeded it in the new structure, or it was replaced by a pianoforte, I have been unable to ascertain; but I rather think it was so superseded; for I do not remember that the old harpsichord maker I knew, who was about seventy years of age in 1833, and who was very enthusiastic about the burnt harpsichord, ever told me that it had Merlin's, and his predecessors', combination of jacks a successor of the same species as itself. As he was with hammers, afterwards carried out by R. Stodart very familiar with the lost one, and, until I showed him and others, is very effective when properly done. mine, would not believe it was possible to make one I knew an instrument of this kind, with two ranks of which could exceed it in power, and felt great interest keys, in a satin-wood case, compass five octaves comin this and other harpsichords generally, often lament-plete, i.e., 61 semitones, which bore the name of Longing our degenerate modern taste for the piano, I man and Broadrip, A.D., 1790, the same date as my think he would have told me if it had not been the last harpsichord. It was a vile piano, restrung with three of its race in the Theatre Royal Covent Garden. I about No. 8 wires to each note, but the harpsichord have since feared showing him my instrument was an action brought out very fair tone, excepting the bass, act of cruelty to the animal, for it dethroned his which being strung much too light was weak. I think favourite idol; he was compelled to admit the greater so well of this combination that it is quite possible I may carry it out in a bichord grand; it affords a very pleasing variety. In page 52, Mr. Brinsmead describes what is termel the old man's head action, i.e., the hammer lifter, which does not escape or hop off like the hammer hiter of a modern piano, whence its not very appropriate name of grasshopper. N.B.-The inventor of this v not John Gieb, as Mr. Brinsmead, who copies the mistakes of others, states, but Christofali, whose se tion has a true escapement. It is by no means "sartain sure" that the old man's head is the very oldest of pianoforte actions. I have gone into this subject in another paper, but will just say that the first record of its alleged invention by Schroeter, A.D. 1716, is subsequent to Christofali escapement action. Maybe the tangent of the cla chord, with clothing on its top, had been used to strike strings (à la dulcimer) before any old man's head (inside a musical instrument) was treated-as it was the custom to treat a traitor's, i.e., stuck up on a stake e pole-for the tangent wire fulfilled this duty to the heal of "ye ancyente man" inside the, perhaps, reversed dulcimer or clavichord with open strings tuned to the chromatic scale. This kind of old man's head, however "soft" (young men's heads never are soft of course! would not " damp," i.e., stop the vibrations of a string unless held against it, any more than a modern pian forte hammer does. Unless the player lifted his fing instantly it would indeed block most "consumedly but it is astonishing what you can do when you ! used to it-like the lucky eels who were benevoler supplied with many skins, and had to endure th being successively taken off. We have Sterne's auth rity that it was nothing (query, to them or the fi wife?) when they were used to it, which they could n well have been if they had not been mercifully provide with many cuticles. I have seen a pianoforte maker's shopman-I sincerely beg his serene highness's pardon for giving him a designation so infra dig., I should have written gentleman; of course they are all gentlemen in so refined a vocation as pianoforte making-the gen tleman, I was saying, who condescended (for a consideration) to play very pleasingly on the instruments in his employer's shop, and to exhibit their excellences (and hide their defects also) from the would-be purchaser, who, probably from his "touch" not having been sufficiently "cultivated," could not play on any of them at all. I say I have seen him ran his fingers over the keys of an instrument (every hammer of which blocked dead against its strings), and lift up each finger from the key just as if the latter had been a "hot potato," supposing so refined a person could have conceived the existence of so vulgar a comestible as a hot murphy necessarily must be, for "are they not sold in the streets," certainly not so cheap as sparrows during the first century, for we don't buy that poor man's luxury, the "hot potato"-by the way, it is considered rich man's luxury at Evans's-quite so cheaply as the market price of sparrows-i.e., two for a farthing-query some other fraction of a denarius. Can it be possible that Queen Anne's, or any other farthings, were then current in Judea ? But not being a numismatical any more than I am a mathematical person, of course I cannot pos sibly know that Caesar's image and superscription were not impressed on farthings. But to come back to or subject, after this slight digression, or compound? digressions, I remark that Mr. Brinsmead states th with the old man's head action the blow was ver feeble, but I may also remark this is not an essentis character of that action; indeed, there can be no diff culty whatever in perceiving that it might be made t impel the hammer with as great velocity, and cons quently cause it to strike as forcibly as the comm grand or any other action can do. Nay, if the o man's head be wide and thin-I forget the ethnological word for this conformation-and it be stuck up rather high (à la traitor's) it is obvious that it will approach nearer to the hammer's centre the further the keys b depressed in front. Now, this condition of things, far from causing the hammer to strike a feeble blow, conduces to the very reverse; for it is obvious that the nearer to the hammer centre the old man's head, or lifter, acts, the faster C.P. it must imp it, and the merest tyro in mechanics knows the the faster a hammer of given weight be impelle the harder it strikes. But, as many persons re semble the writer in desiring the experimentum eruc they can-if so minded and desirous-give the poli man on the "beat" half a crown to try the effect striking their own whole one with his truncheon whe moved at greatly varying velocities. After they have had sufficient experience I can assure them, supposin their previously whole crowns be not "crackit," as the Scotch say-i.e., made into half-crowns, or yet smaller fractions (I hope not vulgar fractions)-in other words, if their thick skulls be not fractured, and their memory totally destroyed by the experiment, that their doubts will be completely solved, and they, being saved by suffering, will become true believers ever after. I feat I shall get but the small thanks for this benevolent good advice (gratis), which, the poet says, is yet its market price. I have been induced to favour the gentle reader with this analysis of this perhaps oldest and most primitive of pianoforte actions, because in comparatively recent times the old man's head-like that of an irrepressible nigger-has popped or cropped up again. The grand pianoforte mechanism of Messrs. Hopkinson is an ar rangement for making the old man's head-in this case literally a wooden head, as usual, but with his hat offdo modern work, and I must say they have made him do his modern work extremely well. Instead of putting his head on an inflexible pole (like that of an ancient wrong-doer, treated secundem artem, according to the humane practice of our ancestors, who put the dangerous class speedily out of pain, and thereby saved no end of money in county rates and model prisons), Messrs. Hopkinson put it on a leg, with a knee joint, so that his old head (modernized to suit the requirements of a pianist of this period) might be made to bow to the requirements of modern society. In their action the old man's head, although it be but a wooden block, cannot block the hammer against the string, because, as in our Schroeter's and Mason's actions, it cannot lift it quite up to the string-in a word, he is a short-legged nnipede. N.B.-This action, although but a onelegged affair, cannot possibly be made to resemble "our Mary Anne's letter," for it don't come (or go) hopping. Unipede as it is, it cannot hop-ergo, it is not properly what is termed a hopper, or, somewhat absurdly, the grasshopper action. To prevent the hammer from rebounding from the old man's head, a habit it had, which was however soft that head might naturally be, or however soft artificially it might be made the torment of the player, Messrs. Hopkinson apply Robert Stodart's common grand check to it; and it is in making provision to allow the further descent of the key, which would otherwise block the hammer against the string, that the ingenuity of its designer, (whose name is Mata, if I don't forget), is displayed. This is effected in manner following:-that is to say, when the lifter has raised the hammer as nearly to the string as it can safely be adjusted to do, a lever comes into action which compels the old man to bend his knee-joint. This not only prevents his head from rising any higher, but actually compels him to do the polite by lowering it. Under these circumstances it is obvious that not only does the further depression of the key bring the check within the radius of the hammer's circular path, but it also, by shortening the hammer lifter, affords ample room between its top and the shoulder or surface of the hammer butt (against which the said lifter acts to raise the hammer) for the hammer to fall against the check. Thus it will be perceived that there is no escapement or hopping off, properly so called, no danger of blocking, but also combined with absolute certainty of the checks acting properly. I need hardly add that the hanimer strikes the strings with just the same force in this as it does in every other action which impels the hammer at the same rate. It cannot be greater or less so long as its weight and velocity are unaltered. It is, in my opinion, one of the very best grand actions in use. It feels extremely nice under the finger, enables the performer to play with great expression, and repeats the blow by a very small rise of the key in front, which is a combination of very good qualities. just been finished) with the same weight as before. Now there were parties there, like some of your correspondents, who thought the valves were spoiled, and that if the regulator leaked the engine would not stand still; but, to disabuse these parties of their prejudicial disposition, I brought it to the level, placed the lever in the centre notch and turned the steam on, but could not get a puff out of her, but by shifting the lever a notch or two she answered to it immediately, but by bringing the lever into centre notch again she came to a stand-still, with the steam on all the time. This, I think, will be proof sufficient for Mr. Wheatley that the centre of link has no motion, provided the excentrics are in their proper places. I will now say a word or two to my friend James F. Ryan. Whenever he makes a drawing of excentric never let the excentric rod point to the diameter; that is not its proper place. The place for it to point is the common centre of excentric, and its vibration is something less than the throw of the excentric vertically each side of the horizontal line. I am very thankful for the diagram for my instruction (or rather destruction provided I swallow it), but beg to say that it is a waste of space, as the same diagram is the production of Mr. Baskerville, of the 17th of June. It is the taking of the diametrical centres that is leading them astray. I now ask Mr. Wheatley and Mr. Ryan of what use are so many notches in quadrant if we have so much motion in centre of link? I always thought the first notch from centre was the minimum, and the end notch the maximum; in fact, common sense must tell them that a link 1ft. 4in. long travelling 54in. each end, but in opposite directions, and each end making the return stroke at the same instant, must make some part of that link motionless as it were. If we put the lever in centre notch we have no motion in valve, but if we place it in next notch we have the amount of motion, and, as I said before, the maxiinuin is when in end notch. Now how can this be unless the centre of link is, as it were, the centre of motion to two distinct levers? If we say we have 24in. of motion in centre of link then we might say that we have three motions in that linkone to run the engine the right hand, the other to run it the left hand, and the third one (which is the 2in. Mr. Ryan speaks about, and the 3in. Mr. Baskerville says the middle of the link should have), or that supposed to be in centre of link, is to run the engine any or no way, but which is the very thing J. W. Bedford wants to get without-viz., "steaming and exhausting when the lever is in centre notch." In conclusion, let these gentlemen draw out a link 1ft. 4in. in length, and take 5 in. as vibration for valve; divide one-half the link in four (treating that half as a lever whose centre of whole is as centre of motion), and we shall have for the end notch 5fin. of vibration, and for the next 4in., the next 2in., and the one next to centre notch 14in. of vibration respectively; and thus we require nine notches in quadrant-viz., four each side of centre notch corresponding to the four divisions of one-half the link, consequently giving us complete control over the amount of opening required for that valve, to suit the difference of loads the engine has to lift or draw. JAMES HARRISON. The remainder of this more or less veracions history I have already characterized. It consists chiefly of matter which Rimbault thought good enough to print, A.D. 1862, from whose work it is copied almost verbatim, even down to the list of patents for so-called improvements in harpsichords, spinets, pianofortes, &c., but in this matter he has indeed gone beyond his predecessor, who terminated the list he published in 1862, with Hopkinson A.D. 1851; following so worthy an example Brinsmead terminates his list, published in 1870, in the year of grace 1862, with the illustrious name of John Broadwood-I beg pardon, I ought to have written, my only excuse is that old associations have such power over us-the illustrious name of John Brinsmead, the alleged father both of Edgar and of cheap pianofortes, Eureka, Magnus, est veritas et prevalebit (query, will, in time, prevail a bit). It is, of course, quite indisputable that among the many patents which have been taken out for improvements in pianofortes since Brinsmead's crowning mercy, A.D. 1862, there could be not even one worthy record, no doubt filial veneration-not to hint at commercial interests-compelled our "Sweet Edgar"--by the way I fear the name of the "sweet" individual recorded by the poet was not Edgar but Edwin, but n'importe, both at least are genuine Saxon, and, as the very practical Yankee philosopher put it "it's all the same and it don't matter." After such a "crowning of the edifice" with the name of the author's respected progenitor, it would ill become a mere outsider, like an ignorant blacksmith, to comment on the refined taste (combined with a somewhat acute HARMONIUM REEDS THEIR CHANGES IN perception of probable material advantage), which is exhibited by the exclusion of so many more recently patented inventions. So having, perhaps you will think, said quite enough already (I fear too much) anent this matter, I to the great relief of yourself and your readers, only say one word more, which word is, Finis. THE HARMONIOUS BLACKSMITH. LINK MOTION. [168] SIR,-I am sorry I replied to Mr. Wheatley so rashly on p. 352. I ought to have taken more time to think it over; but as I am not at home until the week's end, nor do I see my MECHANIC until then, I could not possibly reply as I should have done; this, and the way Mr. Wheatley commences his attack, led me on rather too rashly, but I will endeavour to do better in future. I am very thankful to Mr. Wheatley for reminding me of my want of knowledge of the link motion. He says he is afraid "I know very little of the link motion." I may inform Mr. W. at once that I do not know very much about it, not one quarter of what I should like to know, but what I do know I have proved by experience, having applied the link motion to Cornish valves as well as slide valves. I have also seen the link worked with one excentric and rod. Now if he will make a model of the former (Cornish valve), and one to the latter, I think he will know a little more about this motion by the time he has done so. I may state for the last five years I have had a locomotive to keep in repair, and about two years ago I had to take all the lap off to enable it to go up an incline (that had [163] SIR,-I have read with much interest the discussion on "Link Motion" carried on in the columns of our MECHANIC, and think that it will go a great way in clearing up the very hazy notions entertained by the great majority of working engineers on this beautiful motion. Will you kindly give me space to correct an error into which Mr. Ryan has fallen in the diagram sent for the instruction of Mr. Harrison? In the diagram in question, with the excentrics in the position shown, the rods ought to be crossed. This, it will be evident, very much reduces the amount of vibration. It is quite possible so to proportion the length of the rods that there shall be no vibration. PITCH. R. H. M. [170] SIR,-We ought all to be ready to obey the new "order," which, in right of your premiership, you have issued, calling upon us to see that no question goes unanswered. Every one must acknowledge it to be a good stroke of practical wisdom to exhibit weekly the unnoticed queries," and it should be a pride amongst the subscribers, each in his own speciality of acquirement, to keep the list within the least possible limits. Mindful of the duty, reply to those questions which have personal reference to my own studies. "Amateur Tuner" (4295, p. 407), enquires concerning the tuning of harmoniums; the remarks I make will also answer the question of "J. H. F.," some numbers back, on the subject of tuning. The observation of an amateur tuner is quite correct as to facts: harmonium reeds do fluctuate in pitch under variable pressure of wind, and necessarily so. It is the nature of the free reed. "Freedom" presupposes the tendency to go astray. Stronger wind sets a greater portion of the reed in motion than an average pressure does; lighter wind throws less length into vibration, therefore virtually the reed itself varies in length. In fact, the reeds never vibrate entirely up to their roots, but only more or less in extent according to the degree of force exerted by the wind upon them. Within average force the differences of pitch arising are scarcely observable, although we know they must exist; but when the flexion becomes a strain on the fibre of the metal then the variability reaches extremes, producing dissonance. The predominance of such fluctuations will very greatly depend on the character of the sound-board. Improperly scaled channels favour discrepancies of pitch, whilst truly sympathetic channels have a compensating influence, restraining the wildness of the variations. The defect is not peculiar to harmoniums only, it pertains to all wind instruments, and is but partially overcome or modified by art. The student would do well to remember that every art is a compromise, whether in governing man or materials. After all the skill of the maker has been exercised every instrument betrays imperfections. The soloist on a wind instrument finds that an art of intonation is required, he needs to tone each note as he wants it, and excellence in this gives him supremacy amongst his fellow artists. The questioner will immediately respond-"“I would know this art,"-we can only reply that he must acquire it in patient work; it cannot be told. When we are engaged in finishing and perfecting an instrument we are rehearsing the part of the artist who is to play upon it, reducing the imperfections of intonation, and, as far as possible in us lies, are smoothing the difficulties he would have to conquer himself before his music could give the satisfaction to the ear which both artist and audience desire; hence the anxiety of the artist to obtain a fine instrument-hence the ambition of the maker to produce one. Yet the finest possible instrument leaves full scope for the artist, only that it permits him to devote his, skill to the finer grades of excellence, the rougher work has been done for him in patient rehearsals and repeated trials of effect. Amateur musicians, like amateur politicians, are too much bent on demanding a system of perfection-too much inclined to rely on formal methods, and to think that everything may be done by rules and regulations. In respect of musical instruments they will soon find it is not so; experience will show how much they must of necessity yield to the peculiarities they meet with in order to attain real utility. It is best to recognize defects as inherent in the nature of the harmonium, and we are then better able to judge how far they are to be influenced by skilful treatment, or veiled by art, and perhaps made subsevient to agreeable results. The practice of tuning, although so important a matter for music, is but distantly related to musical feeling; it is an arithmetical operation, a calculation by the ear. Many of the best tuners have been men without musical knowledge, and devoid of musical feeling; the talent is special, like the talent for figures, even as a man may be a good accountant yet possess no aptitude for the conduct of trade, or may be a good architectural draughtsman, yet have but little sensibility to the painter's effects of colour. Supposing a man has a talent for tuning, it will require from two to five years practice to render him competent. I cannot, therefore, advise the amateur harmonium builder to undertake tuning his own instrument; his desire of assuring his friends that he did everything himself ho had better sacrifice to the more humanising regard for his friends' ears. It is hardly probable, under the most favourable suppositions, that he would be successful in his early efforts in tuning-his time would be wasted and the practical usefulness of his instrument be lost; for I take it to be that it has some musical service in its design, and has not been got up as a child's puppet-show for friends to be condescendingly interested in. An harmonium intended for use should, if possible, be tuned by a practised tuner, who, if only of moderate skill, will have an advantage over an inexperienced hand. It is then open to the possessor to make whatever incidental changes his own taste may suggest; indeed, it is likely that minor changes and shadings may be desirable, for it is not every tuner has an ear for quality, and the amateur who possesses the higher susceptibility to musical feeling may thus find ample range for exercising his skill; and should his temerity lead him to any extravagant temporary derangement the tuner will be able to bring it back again into a sane condition. The amateur bent on experiment and content to spoil a set of reeds would do well to get up an extra specimen and test it by side of the professional work; he will learn more by this than by his own unaided efforts. Instruction in the arithmetics of tuning should be sought in one of the manuals on the subject; unless entered into with thoroughness of detail an exposition in these pages would be useless, and therefore I prefer to advise the study from its rudiments. A little book, at a shilling, called "D'Almaine's Art of Tuning," may be obtained through any bookseller. In the process of tuning the bellows should always be kept as nearly as may be at one even power, about half the strength of springs, remembering that single notes tuned will show more variation under changing pressure than will be exhibited in actual use when chords and running passages distribute the strain of the wind. A discreet tuner strikes the mean in the general display of the instrument, humours each reed according to its strength or weakness, and endeavours to leave it in that condition which, on the whole, will be most generally serviceable in combinations of chords and most agreeable in the average effect; for the tuner should also be able to associate the voicing and regulating the reeds with the more mechanical operation of tuning. The ability to do so is rarely found, but when it is, that tuner is highly prized. No two tuners tune exactly alike, and there are different systems of tuning adopted from personal preference. It is an accepted doctrine that all octaves should be tuned perfect. As regards the harmonium this doctrine I do not hold to, believing it can be shown as theoretically reasonable, and practically more agreeable that they should be something less than perfect; but this and many other matters in tuning form too complex a study to be understood by a merely cursory HERMANN SMITH. explanation. C A TELESCOPIC. nearly two years' experience in the delightful exercise and pleasure of bicycle riding. As regards learning to ride I accomplished that in about an hour, on an incline of a hundred yards or so. I first learnt te balance myself on the machine by taking my legs of the ground and letting the bicycle run down this incline I then placed one foot on a treadle and got it into the motion; then the other foot's turn came, and last all I placed both feet on the treadle. After occasiona practice for a day or two I could ride the machine nearly as well as I do now. I find, like T. Cooke, the best and easiest way to propel the machine is to plac the seat well back on the spring, so that one can gives forward-downward push instead of only a downwar one. Riding on this plan, I can beat all the riden position coincides with the bearing by mariner's com- in my part both in speed and distance, as the motion is [171] SIR,-In accordance with "C. G.'s" request called a rhumb-line, which cuts all the meridians which the machine from side to side of the road, showed the pass. They therefore steer their course by what is not so tiring, &c., as the other. The twisting about d (p. 430) I give him a method by which he may find the it crosses at equal angles, as the magnetic needle does; either the rider was not up to his work or that his proper diameter of a plan for any sized Newtonian rebut the angle of position shows the true bearing of one machine was out of order. I have not found a flector. The aperture of the speculum being given, its solar place from another upon the earth, or the direction danger to result from riding a bicycle in narrow rad which a ship would take if the two places were in sight and unless a rider should lose his presence of mind, e focal length is next found, and a diagram (similar to of each other. The angle of position of a star, which I be unable to manage the machine, I do not think that given above) is to be correctly drawn to any conunderstand is used in some astronomical calculations, is accident likely to happen. venient scale; previous to this, however, the largest the angle which that particular star makes with the pole perience, of the danger or otherwise of jumping I cannot say, from e field and lowest power eyepiece proposed to be used of the ecliptic and the pole of the equator. Thus let P to the saddle when one wishes to mount, but I shou with the telescope is selected, and the diameter of its (Fig. 2) be the pole of the equator upon a celestial globe, think it is a dangerous practice. I should recomme field lens measured. In the diagram, S S represents and P the pole of the ecliptic, and A the star Arcturus; a would-be purchaser to buy a machine of sne the speculum, and the short line F F its focal length; then the angle P A P would be the angle of position of height that he could touch the ground with his a upon this line the eyepiece E is supposed to be placed the star Arcturus. These angles of position may be when mounted, and he will find it a very great a in such a position that the diaphragm is coincident with the line F F. The diameter of the field lens being determined by the globe approximately; that is, suffici-venience. A good rider never, or very rarely, lose correctly drawn to scale, next draw lines A A and B Bently near to enable us to compare their results with power over the bicycle. The great secret in turn those which have been worked out by the formula in corner, &c., sharply, is "never take your foot off the from the extreme margin of the lens to the margin of trigonometry. If, for instance, we wish to find the side pedal or treadle," or the pressure exerted by a the speculum, and these lines will represent the practical working limit of the cone of reflected rays. The angle of position between London and Constantinople, outside foot overcomes the inside, and down yon go. next thing to be found is at what point ought the plane (Fig. 1) we must bring London to the meridian, and to intersect this cone of rays. This is found by first having screwed the quadrant measuring the semi-diameter of the telescope tube and over it we must pass its graduated edge over Constantiadding to it the distance beyond its outer side at which nople, and measure the angle the focus is supposed to be thrown. Suppose, for inupon the horizon (taking care stance, the tube is 10in. diameter, and the focus F F to have London in the zenith), is 3in. distant from the large tube, the total distance of which will be found to be 104° the focus from the centre of the plane would have to from the north towards the be 8in. This then would be the distance of the centre east. To find the angle of of the plane C C, from the focal line F F, and the diaposition of Arcturus by the meter of the cone of rays at the line C C, gives the size celestial globe, we must bring required for the actual aperture of the plane. It is of Arcturus to the zenith, then course, advisable to have the plane just a trifle larger we can chalk out the triangle than the cone of rays demands to admit of necessary play in its adjustment. or pass the quadrant from Arcturus over the pole of the ecliptic and we shall find the angle on the horizon, viz., 22° 26'. We shall then be in a position to use the formula to verify our results; and the formula for this purpose is the same as used to find the shortest distance between any two places, namely, Given the two sides and the included angle to find the other angles. The two sides will be the complements of the latitudes and the included angle the difference of their longitudes, and the angles at the base will be the angles of position of the two places; but to find the angle of position of a star, we have three sides given to find the angle A. The three sides are P A the complement of the declination, P P the obliquity of the ecliptic, P A the colatitude, and the angle may be found by the formula This, I believe, is the most correct rule; but to those who desire a simpler method I may say that if the plane is 1-5th the diameter of the speculum, that will be found sufficiently correct in most cases. As to "C. G.'s" query respecting the polishing of specula, I may say that, in general, fitfulness of movement arises chiefly from irregularity of size in the facets of the polisher, and may be almost entirely overcome by attention to this point. I find the time required to produce a good polish is from three to four hours, but this varies according to the hardness of the glass and the amount of cohesion between it and the polisher to harden. The pitch rosin may be added, or (as Herschel recommends) it may be melted with sufficient heat to vaporize some of the essential oil which it contains. I find this quite as effectual. W. PURKISS. FIG. 2 100 FIC.I cos A Sin s sin (s a) The leg guards, which are generally fitted to bicycle now, effectually prevent all splashing and rubbing the thighs. "Husband" has given the best mode taking a bicycle up hill, and like "E. S." I shall believe in ruptures when I feel the effect of them. MUZZLE LOADEE. "INDUCTORIUM'S" COIL. [175] SIR,-I must apologize for not sending you the description of my coil before; I do so now, trusting it may not be too late for the several correspondents who were inquiring about it. In the Exhibition of 1851 there was a large coil by Siemens and Halske, made on the vertical principle, which gave extraordinary results, as perhaps some of our readers may remember. This coil was made out of a solid block of ebonite, cut into parallel grooves, into which the secondary wire was wound, the primary being quite detached and slipping into a core in the centre of the coil. Now it occurred to me that it was an unnecessary trouble and expense-which in a large coil would be immense-to cut these vertical channels out of the solid ebonite, as the tension in each of the compartments, if they were made small, would not be great enough to leap over the interval between each alternate channel; accordingly I proceeded to construct a coil as follows:-I give the size of my present one; your readers can alter the size to suit their ow several requirements. I took an ebonite tube about 18in. long, Sin. in bore, and fin. thick; on each end I cut a screw on exterior, for about 4in., and on them I fitted two (all ebonite), 5in. in diameter; these nuts form the t leaving about 3in. of the tube clear at each end—this ends of the coil, and serve to screw the discs all together. very important. where 8 denotes half the perimeter of the triangle. B C. DISSOLVING VIEW PAINTING. T. S. H. ebonite, No. 20 wire guage, so as to slip on the ebonite division double that of the two ends; this is also im READINGS FROM THE GLOBES. [172] SIR,-Geographers have fixed upon the latitude and longitude of a place in order to determine its position upon the terrestrial globe; and astronomers have fixed upon the right ascension and declination of a heavenly body, or upon its latitude and longitude, in order to mark its place upon their maps and celestial globes; but mariners, besides latitude and longitude, require the course which a ship ought to take upon the pathless tracks of the mighty deep, as without correct guidance they may endanger the safety of their vessel. As they make use of the mariner's compass to direct them, it is necessary for them to know upon what points or rhumb-lines they must steer in order to reach their destination; and con[178] SIR,-With your kind permission, I propose, in sequently the value of accurate knowledge upon these the course of a few weeks, to offer a detailed and practical Thus then I have 90 dises or thin rings, 60 of which points cannot be too highly estimated. We propose course of instruction on the higher class dissolving are 4in. external diameter, and 30, 5in. I have als then (1) to define the angle of position between two view painting, the result of nine years' experience. It 90 small rings, fitting the tube, and fin. square. I then places upon the earth's surface and the angle of posi-is a fascinating pastime, and the great enjoyment it build up my coil as follows:-I screw on the nut a tion of a star; (2) to show how to find such by forming enables one to afford others is to me its strongest re- one end, leaving about 3 in. clear from the end, then! the triangle upon the globe; and (3) to point out how to commendation. To place glass-painting within the put on a small ring, then a thin disc, then a ring an verify the results by working them out by the proper printed outlines and photographs are sold for colouring arranged; taking care, as I said before, that the large reach of those who cannot make their own drawings, another disc, and so on, till the whole 90 are thus formula for this purpose. The angle of position shows the true bearing of one place from another, or the by most opticians. Of these I hope to speak in a suit- 30 discs occupy the central part of the coil; then exact direction which the arc of a great circle would able place, but I state en passant that nothing surscrew on the nut to the other end, and make all tight. will always keep its place in the market, and command hole drilled through it, just above the small ring, for passes a superior “hand-painted slide in oils," which I ought to mention that every alternate thin disc has a simply for the encouragement of the earnest-minded, wire in each hole previous to putting them which I venture to remark, as a nameless one, the wire to pass through, and I put a small loop of of skill to the work, that when I took up the art, I without this forethought, is very troublesome to do. who can bring patience, care, and a moderate amount a convenience for pulling the wire through; which, conid but make a modest vignette in tolerable drawing, On the two ends are screwed two supports to attach the later views (on the Rhine) for ten shillings each. If and only a short time since I disposed of some of my coil to the base board. which, by the aid of our invaluable paper, I may give, those interested will kindly follow the directions, &c., its price. take to reach it; and this great circle is represented by the quadrant of the globe; but it is necessary to bear in mind that it is not the direct course which a ship must steer, for the magnetic needle being of small size as compared with the bulk of the earth, makes equal angles with every meridian over which it passes. Thus, if a ship were guided by the mariner's compass, according to the true bearing, as found by the angle of position, it would make equal angles with every meridian over which it passed, and would be carried out of its right course, for the quadrant of altitude or great circle does I think I shall be rewarded by hearing that many presently. Slip the end of the wire, by means of the will have produced things of beauty that will remain SABLE. not make equal angles with every meridian over which THE BICYCLE. Now for the winding. Don't wind in the lathe. I two axes with two handles.-the object of this will be seen made a temporary stand, and supported the coil on (supposing you to begin at the left hand); then wind loop before mentioned, through the hole in disc No. 2 and fill up the first channel, the end of which will be the left-hand terminal. Then turn the coil round, join on the wire to the end you pulled through, and fill up the channel No. 2, but wind the reverse way to No. 1. again reverse the coil, and proceed as before, and so side ends of every alternate pair together. The coil on till all the channels are filled; then solder the outwill thus be filled with a continuous spiral of wire joined, or connected alternately at the inside and out. side of each channel. Before winding the wire, soak the wire in a boiling mixture of 3 parts of paraffin (solid) and 1 part white war-this is most important. Perhaps it would be better, though more trouble, to let it pass through the hot solution as you wind it on. I used the former method. I think I have clearly explained my plan of construction as regards the secondary wire. I may mention that my primary consists of No. 10 cotton-covered wire, wound in three layers on a bundle of soft iron wires about 1 in. diameter. The wires are slightly insulated by a covering of tape soaked in paraffin and wax, and each layer is also insulated by a few thicknesses of gutta-percha tissue. The whole, when wound, forms a cylinder which will just slip into the ebonite tube. In a coil of this construction it is impossible to break down the insulation if your tube is a good and sound ane; and the insulation of the wire with the paraffin stops all small leakages, so that you utilize every part of the induced current, and hence you require very small battery power. The one that I have described has given good thick sparks of from 8in. to 4in. in length with one cell of Groves's battery, the platina of which is 2in. by 4in.; and the secondary wire that produces this extraordinary result is, as nearly as I can calculate, about 4 miles. My condenser is made as follows:-I took about 60 sheets of ordinary good demy paper. I had a sheetiron dish made, about the size of the paper, in which I heated, by a Bunsen's burner, the above-mentioned mixture of paraffin and wax. Into this boiling mixture I dipped each sheet. I find, however, that it cools so quickly that it has not time to drain off; so that there is much more than is required. This is easily obviated by holding it before a fire, and it will drain off, leaving, when cold, a beautiful pearly-looking sheet of splendidly insulated paper. And the whole process is so simple and expeditions, not occupying, for the 50 or 60 sheets, about a square foot in area, d fff B [177] SIR,-In the 239th number of the ENGLISH MECHANIC appeared an article entitled " Astronomy and Photography in England and elsewhere." I must confess that after reading it I could not help experiencing feelings somewhat akin (as I imagined) to those of the writer of the article; and those were of extreme dissatisfaction at the results of the English operations in India last year during the solar eclipse; and also respecting the state of celestial photography at Kew. I do not purpose in this communication to go into the photographic chemistry as practised in that establishment, or as practised by the photographic section of the Indian expedition, but to draw the attention of your astronomical contributors and readers to a few remarks in the above-mentioned article, as it is likely to lead into wrong paths of inquiry, to avoid certain defects such subjects are liable to, one of which was present in those otherwise splendid American photographs of the solar eclipse last year. The writer alludes to a phenomenon I investigated some 9 years ago, the results of which I communicated in 1861 to the London Photographic Society, and again, more recently, to the photographic journals. These remarks are as follows:"It is interesting to note that the well-known line of increased light, which is frequently seen in photographs in which a light and dark object are in immediate contact, is noticeable in all the prints of partial phases of the eclipse, the line of light being on the sun's disc, where the dark edge of the moon is immediately in contact with it. Whether this is due to light reflected from the back of the plate, or to the tendency of development to increased reduction of silver on the edge of a light part in contact with a black, upon which silver is deposited, is uncertain." It is this line of light or halo, associated with a light and dark body when in immediate contact, that I wish to direct attention to. I have not had an opportunity of examining these photographs; consequently, I must be guided by the writer's description of them. He speaks of this line of light as "being on the sun's disc." This I presume is the fact. What about the cause? Concerning the latter the writer seems to be undecided, as he says it may be due to reflected light from the back of the plate, or to undue deposition of reduced silver. This statement seems to me to indicate a little confusion of ideas. He makes mention of two causes, each of which is likely to produce the effect mentioned. The first of these causes, some two or three years ago, I designated as "optical halation; " the latter as "mechanical halation." Now any jone who has studied the subject of photographic halation must be familiar with the two kinds here mentioned. They are two distinct phenomena, and give rise to two distinct effects, and consequently can be traced to two distinct causes. The appearance known as optical halation is a line of light on a dark object, which is in immediate juxta position with a light object, and is traceable to reflection of light which has passed through the film which has been acted upon by the bright image. This reflection is effected by what is commonly known as internal reflection of the glass-the negatives, of course, being taken on glass plates. But the spreading of the light is effected by means of the semi-transparency of the film. The remedy for this defect is to make the back surface of the glass plate non-reflective, either the whole of the rays penetrating the film or only those which have a photogenic effect on the film. This is [176] SIR,-In reply to "Faber" (4330), the pre- done by bringing into optical contact with the back paration of a wall for fresco painting is a work of time surface either a black or yellow substance. When this and great carefulness, for on the goodness of the work is done, the line of light on the dark object in the picdepends in a very great measure the durability of the ture (positive) disappears. But the writer of the article painting. If the wall is already covered with plaster alluded to says that the line of increased light or halo or laths it should be cleared, and the bricks thoroughly is on the sun's disc, so the effect on the American scraped and afterwards well chipped. See that the photographs cannot be due to this cause. Besides, bricks are in good condition and perfectly dry, and the Americans were the first to apply this principle to then proceed to lay on the first coat, consisting of river rid themselves of this defect. Whether they did so on sand and the best old lime, mixed to about the usual this occasion would depend upon the necessity for it. thickness. This should be laid on so as to leave a If their chemicals were in such a state as would allow level but rough surface. At some places on the Con- of the use of thick films they might be able to do with tinent small flint pebbles are mixed with this compo- out any backing to the plates. sition to give the requisite roughness. This groundwork should be allowed to dry thoroughly; indeed, unless the lime is old, it will be some considerable time before it will be safe to put on the intonaco or painting-surface. This should be prepared with the very best old lime, perfectly free from grit. An excellent material is prepared from the limestone of Dardham Down, Bristol. The lime is mixed in troughs to the consistence of milk, and is then passed through hair sieves into jars, where it is allowed to settle, and the water is poured off. It is then ready to be mixed with the sand (fine quartz sand, well sifted, is the best), in the proportion of one part lime to two parts sand. The implements used to float on the last cont are made of wood or glass, but trowels of iron may be used if free from rust, and care is taken not to press the iron too forcibly on the intonaco. When the lime and sand coating is ready to be laid, the rough cast must be wetted thoroughly, and the intonaco floated on in two coats, the last with rather more sand than the first. The thickness of the two should be about 3-16ths of an inch. After these are spread, go over the whole with a roll of wet linen, which will remove the marks of the trowel, and prevent the surface being too smooth. more than an hour, or two at the most. I send a small sketch which may make my description somewhat clearer. I trust that this description may be of some assistance to your readers. INDUCTORIUM. P.S.-My thanks are due to "Sigma" for his notice of the air-pump. I wish he would state definitely what vacuum he got with a Tate's pump by the gauge, as I have one which I cannot get to act at all well. I am making one on Newman's plan, the result of which I shall be glad to let your readers know, if interesting. Can any one inform me the best oil to nse with air-pumps, that will not get thick and clog the valves ? All that I have tried do so, and thus impair their action. WALL DECORATION. Now that we have eliminated one of the supposed causes of the defect, we are in a better position to deal successfully with it. We now come to the increased line of light on a light object in juxtaposition with a dark object. This is brought about by quite a dif ferent cause, which is probably mechanical, though peculiar conditions of the chemicals may favour its development more at one time than at another. It will be interesting to know whether rapidity or slowness of development of the image has anything to do with it. Be this as it may, it is a common practice during development to give the plate a rocking movement with a view to mix the developer and silver thoroughly together and so bring about evenness of development. If one part of the film is not exposed at all, and another in close proximity is well exposed, the developer which is in immediate contact with the film of both will be dissimilarly affected. The one over and in immediate contact with the unexposed part will be the richer of the two of silver particles, this by the tilting of the plate will be brought over the part exposed, the extent will be proportionate to the kind of rocking movement given to the plate. The result of such movements will be that the edges receiving a richer supply of silver from the unexhausted parts will be developed more than those having the old developer continually passing to and fro over their surface. This I am disposed to think is the cause of the increased line of light on the sun's disc as represented by the American photographs. In order to obviate this defect, I would suggest that the plate be moved about as little as possible, or the solution be poured on and off-first from one end and then the other-or by developing in a bath. The latter, at first sight, would seem the most promising, as it would give a free supply of developer, and that too of more uniform strength over the whole surface than can be obtained by the usual method. Our English operators will do well to see to these matters before the next expedition sets out on its journey, and be certain that all has been done that can be done to remedy these defects, and let us see, on its return, that its photographic operations have been at least equal to the Americans', if not superior to them, if that is possible. Those interested, and requiring more minute purticulars, will find the subject fully discussed in the following papers, to which I have had the honour of communicating my views from time to time :-The Photographic Journal, Nos. 108 and 110; The British Journal of Photography, Nos. 140, 226, 233, 239, 426, 431, and 460; The Illustrated Photographer, Nos. 22, 25, 28, 32, and 56. G. MARLOW. ACCIDENTS OF THE WORKSHOP.* [178] SIR,-As the British and Foreign Mechanic is now amalgamated with the ENGLISH MECHANIC I send you the continuation of this subject, which was commenced in the first named journal on July 2, p. 342. It may be as well to give a short résumé of the contents of the previous part. The mechanic, always in the midst of moving machinery or climbing scaffolding many feet from the ground, is continually liable to accidents, and a knowledge of what to do, and what not to do, will be found of very great use. In the first place, where the accident is apparently serious, the clothes of the injured man should be loosened, and he should be laid on a door, or shutter, or a plank. An attempt should be made to discover whether any bones are broken, and if there is profuse bleeding it should be arrested immediately. Where there is a cut or gash, if the blood is scarlet and comes in throbs or jumps we know that it is arterial blood, i. e., comes from the heart; bleeding of this kind is stopped by tying a ligature (a narrow strip of linen) between the wound and the heart. But if the vital fluid is of a dark colour, and flows steadily in a stream it is venous blood, and is going back to the heart; in this case the ligature should be tied or pressure applied between the extremity of the limb and the wound. After the wound has been well washed, a compress of a pyramidal form made of linen rags or lint should be applied, apex downwards, and bound firmly round with a bandage. Before applying the bandage it should be saturated with water, or a little simple ointment placed on the part next the wound. If the gash is long a stitch or two should be passed through the edges with a bent needle and silk,— each stitch tied separately. If the bleeding of the artery be stopped by the pressure of the finger or the ligature, the compress may be dispensed with, and a piece of lint folded three or four times placed over the wound and bound down with a bandage. If the wound is of such a nature that pressure will not arrest bleeding, especially where one or more of the arteries of some magnitude have been severed, more forcible means must in these cases be applied; the offending artery must be sought for, and when found drawn out by means of what is called a tenaculum, which resembles a shoemaker's sewing awl; when this is not at hand a large pin bent, or a pair of tweezers with fine points; may be used. When the artery is pulled forward it should be tied with some thread two or three times double, and if there are others they should be treated in a similar manner. It must be observed that the extremity of the divided artery nearest the heart should be secured. After the blood vessels have been tied the wound should be washed, if caused by an instrument covered with foreign matter, or if not it is always well to cleanse it; but allow as little water as possible to enter the opening, for it has a tendency to swell the flesh and increase the gaping, especially if warm water is used. Any piece of glass or dirt may be removed by dry sponge. When cleansed the edges are to be brought together with a few stitches or adhesive plaster, and a bandage bound round in the ordinary way. This should be removed daily to see whether the wound is inclined to slough or discharge matter; when such is the case what is called the "water dressing" should be resorted to this is merely the bandage or rag covering the part to be kept saturated with water. In some cases 'proud flesh" may form; then, as in sloughing, a little nitrate of mercury ointment may be applied. It is best, on the whole, not to meddle with the dressed wound more than to keep it clean, which is a great thing, for it must be borne in mind that the best healing doctor in the world is nature, she can and does perform what no human being can or ever will, and the surgeon's motto is to assist and not interfere or interrupt nature. When it is found that the edges have adhered to each other the stitches may be removed, also the bandage, and a little simple ointment applied on some lint or linen rag, which will prevent the part being injured by dust and other irritating matter, and assist in healing the wound by excluding the air. The cause of wounds being irritated and prevented from healing through not being excluded from the air is from the fact that the atmosphere is impregnated by millions a * The right of translation and reproduction reserved by the writer. of minute invisible animalcula which is so elaborately explained in Professor Tyndall's lecture on "Dust," which I should advise all my readers to obtain. This savant has demonstrated beyond all reasonable doubt that were it possible for all the air we breathe to pass through a filter of cotton wool before entering our lungs that life would be prolonged many years. In proof of this observe the advanced age to which farm labourers live to what those do who are living in the foul air of our great cities. But I am going from my subject, though I could write many pages on what I have just alluded to, but it would be turning from the path upon which I have set out. Other means are to be adopted when the hemorrhage is obstinate, such as the application of ice or very cold water to the part. Cold is one of the best stiptics we have, and seldom fails to do good; it not only contracts the gaping mouths of the arteries but also those of the wounds, thereby arresting bleeding. The ice can be applied directly to the wound, if clean, or be wrapped in flannel or a piece of linen rag, and on the cessation of the flow the wound bandaged as before directed. Cases have been known where the artery has only been partially severed; in such instances contraction is impossible; therefore it is necessary to complete the division with a lancet. This should be left for a medical man to do, for it is an operation that requires a knowledge of the venal and arterial system. It should on no account be attempted by a novice, unless medical aid is unprocurable, and this appears the last resource to save the person's life by stopping the bleeding. This is founded on the known tendency of arteries to self-contract on division. The danger in this operation is that an inexperienced hand may, instead of completing the division in the already wounded vessel, injure others in the act, and so in trying to do good do a great deal of harm, and make matters worse than before. The safest and surest mode of arresting hemorrhage, when the wound is of some magnitude, is by tying the blood-vessels; this, when effectually done, is unsurpassed by any other means relating to external bleeding. It should be borne in mind, that all the arteries must be secured, else bleeding may proceed after bandaging, and the patient unconsciously lose an alarming amount of blood. In my next letter I shall speak of internal hemorrhage. FREDERIC J. M. BUTT. which a given or known volume may be abstracted for the special determination. The chlorine, sulphuric, and carbonic acids may be thus determined, as also the amount of hydrate in the free state. From the result of this analysis, we calculate the percentage composition of the liquor, and having that knowledge, we may readily form an idea of the quantity of caustic soda or crystallized carbonate which may be obtained from it. Theoretically, 62 parts of anhydrous soda should produce 106 parts of anhydrous carbonate, 286 of crystallized carbonate, or 80 parts of the hydrate. 80 parts of the hydrate would of course in its turn form the same quantites; but if it only contained 60 per cent. of the hydrate, the quantities obtained would be 3-5ths of the above-viz., 63-6 of anhydrous carbonate, 171-6 of the crystals, and would only correspond to 37.2 parts per 62 of anhydrous soda (NagO). GEORGE E. DAVIS. THE SUN'S PARALLAX. [180] SIR,-Allow me to say a few words in answer to "Veritas's" letter on page 425. It is evident that if the data of a calculation be correct, and the reasoning false, the result must necessarily be incorrect. Now, in my letter, on page 402, I wished merely to point out the false reasoning, and correct the error of "Veritas." And if we assume the data given by him on page 228 to be those "which are generally accepted to be true," it is plain that the parallax found by him in the same letter cannot be "that which is generally accepted to be true," because the reasoning is false. For aught that I know, not being an astronomer, the parallax may be correct, but if so, the data cannot be. Surely "Veritas" does not want figures to enable him to see this? HUGO. LATHE CONSTRUCTION. ᅲ 14489-216 29744.5121b. Since C S = = 12 12 x x 2 12 = 14489-216 .. (12+)3 [181] SIR,-I am sorry not to be able to comply we have WEIGHTS OF CHEMICAL SOLUTIONS. To use Dalton's table the specific gravity must be known; and this is calculated by multiplying Twaddell's degrees by 5, and adding the results to 1000:80° Twaddell x 5 = 400 1000 The above will probably not be of much use to "Alkali;" I merely give it, thinking it may be of some use to a few of your readers-saving them the trouble of calculation, &c. "Alkali" must remember too, that the above table is for the percentage of soda when present in solution as a hydrate, and not as a carbonate; in which latter state it is present in black ash mixed with sulphate, sulphite, or sulphide, either separately or together, with a little hydrate and some undecomposed salt; it will therefore be seen that the table is useless for the estimation of the carbonate when it is present in solution. The only connect method by which the exact composition of the liquor may be known is by an analysis; this may be either gravimetric or volumetric; the latter is preferable in this case. The filtered liquid is diluted to a given volume, from yields to none for accuracy in putting his work together, commencing about October, 1846, when I saw the first pieces of his lathe in hand. As it is, however, I cannot undertake to go down to Yorkshire and spend a week making drawings and putting together again all the things I should have to take to pieces. Had I fancied fancy work, I should have done so long ago. If the R.E. Captain is stationed at Chatham, I may in my capacity of Engineer-Volunteer officer, have the pleasure of being in his company at the Field Works Inspection there on an early day, and shall be glad to discourse on the subject of lathe work. CONIC SECTIONS. J. K. P. I [182] SIR,-While thanking "F. R.A.S." for his reply, it being hardly an answer to my question, may observe that it is scarcely what I require? I hope that I may consider myself sufficient of a mathematician to understand, at least, the rudiments of conic sections. What I wished was for your correspondent to decide if the definition I gave was correct, as, a dispute having arisen at a recent meeting of the Mathematical Society that is based on it, I was asked to get it decided. The point, therefore, is, Is the definition I gave rigidly correct? Also, the vertical plane of a conic section is the plane passing through the vertex and parallel to the plane of the conic section. That the circle is a conic section is of course indis. putable, but if it may be regarded scientifically as an ellipse the definition of De Morgan, that all ellipses have two foci and a minor and major axis, will be ap THE MICROSCOPE. [183] SIR,-I shall have very much pleasure in acceding to the request of "An Axmouth Resident" (see letter 124), and will with your permission, provided no other correspondent volunteer in the interim, commence a series of articles on "The Microscope: How to Choose and How to Use It," in the course of a few weeks, say about the third week in August. As regards mounting in Canada balsam, your correspondent finds, as have all mounters, that air bubbles are a plague and a vexation. If the balsam be tolerably fluid he has only to keep his slides for a few days at about 70 deg. to 80 deg. of Fahr., and the bubbles = 4528-194lbs. ... 12 + x = 16-54 .. = 4·54 GAS BY A NEW PROCESS. [185] SIR,-I have copied the following t Times newspaper, a few years ago. I forward t with the hope that some one (or more) out d numbers of readers of our MECHANIC can mana an apparatus of the kind, and also understand process of the manufacture of the gas afterward there could be found among the many readers could and would do this, I am sure of this he w get an immense custom, and it would be a bus numbers-your humble servant for one. "GAS BY A NEW PROCESS.-An experimentis lighting, by Count le Val Marino, was made yester evening on a piece of ground at the back of Pete lane. A small gasometer was erected which we nected by tubes to a furnace, containing three re one of which was partly filled with water; a with tar; and both being decomposed in the retort, formed the sole materials from which the was produced. The process appeared to be extre simple; and the novelty of the experiment consis employed, though the inventor says that any k the fact that the water and tar were the only mass bitumen or fatty matter would answer the pe equally well. After the lapse of about half an turned into the burners, and a pure and powerful after the commencement of the process the gas was produced, perfectly free from smoke and pleasant smell. The great advantages of this over that produced from coals consists, it is said, 1 with which it is manufactured, and the perfection the cheapness of its producing materials, the fa which it is at once brought without the necessity of i undergoing the tedious and expensive process of codensation and purification, for in this instance as soot as the preliminaries were completed, the light was produced in a perfect state within a few feet of the gasometer which, although of inferior size, was said to be capable of affording light for at least 500 lamps or burners. The price is estimated not more than one-third that of coal-gas, equally available for domestic use, and such that small gasometers might, at a trifling expense, be fitted up at the back of grates in private dwellings, from which the gas could be conveyed in India-rubber bags to any part of the house, thereby preventing the many accidents which occur by the use of tubes or pipes."" I do hope we shall hear from some of the readers of our MECHANIC that they will at once undertake the manufacture of the apparatus, and for trifling royalty instruct any person in the process and manufacture of the gas. JOHN FLEET. |