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which is not reedy in tone, not unequable in register, rvnd ia instantaneous in articulation, is a great musical boon. That any one, once accustomed to a Mason k Hanilin, would of liis own free will go back to the harmonium, I cannot believe. Mr. Nash thinks that "for certain pnrposes " a person might even be beguiled back to tho buriuoTiium. I confess I can only imagine one BTwh purpose , and that is, by contrast, to endear him still more to the beauty of the American organ. It

is the oltl story of the part discords play in music;

they make the harmony sweeter and more precious.

JSlJSTACU HlNTON J OWES

[38*21 Sib,—I do not know on what footing Mr. E. 11. Jouca cant undertake to decide ex eattudra where Bo many doctor* disagree upon the respective merits of an harmonium proper and the harmonium improper yclept American organ. It was an old discussion in these columns, Mr. Editor, in the timo of your predecessor, and in them the opinions of Dr. I'ssher and of Dr. Leslie naed to bear testimony to the super-ex eellonce of the new instrument; but the flood of light !■ ( in upon tho snbject, and the experience resulting from many months' trial, have vastly modified at least one of these learned doctors' opinions. The other is capable of speaking for himself. In my humble opinion, it in rather unfair to your space thuB to resuscitate the ghosts of hosts once slain; but at the risk of being tedious, I niust join the ranks of your last correspondent, Mr. Nash, m temperate and faithful defence of the cause of harmoniums vr.rtutt American organs. Now, I think that though Mr. E. H. Jones's attack npon the harmonium is his strong point, that his dofeuce of the American organ is his weak side, and this latter I will examine first. As you arc aware, I am not insensible to, and I have before given expression to my appreciation of, what are the merits of the American organ, and it is needless that I should repeat here what I have before written on the snbject, and which I find no cause to alter. But what is it that Mr. E. H. Jones can say in its favour? I have read and re-read his letter for the sake of being impartial, and if he linds my analysis correct, I fear that if he hot* paid !K) guineas for a No. 4ti fct-stop tircavington ho will bo obliged to reconsider tho meritorious* points of his instrument in order to write of it in a more eulogistic strain than pervades his first composition. The total of what Mr. Jones can Bay in its favour I will reproduce from his letter in a few words. First, he says, *' the tone is round and pure;" "His resonant;" "it is pure;" "it is pure audtrue;" the intonation is perfect;" "it approaches the organ tone in quality.'' In addition, he claims that '* the touch is as rapid and as delicate as a pianoforte," but has no more eulogy for the quality of tone, nor for the variety of timbre which can be attained by means cither of the reeds or their separate chambers, or their resonant sounding-box, or the exhaust bellows by which air is drawn throngh them; so that his communication sins more from faults of omission than commission, except his ungracious attack on the harmonium, the defence of which instrument is foreign to the purpose of my letter. Now, my opinion is very well made up on one point—that is, that yon can neither expect nor produce from the rends adopted in the American organ more than one timbre or quality of tone, and I gather from my Utu experience and from your correspondence, columns that the great desideratum in reed instruments is variety of timbre, or, in other words, variety of voice.

Seeing that every reed in an American organ is voiced in precisely the same manner, i.e., by having a little corner of its tongno curled np, it is forced to speak in a manner a little less freo than the ordinary reed of an harmonium. This little disposition of tongue-(iedniicx, combined with due arrangement of chamber and case, gives rise to that quality which is its speciality ; beyond it you cannot go, and every fresh rank only being permitted to speak, in this identical manner limits the capabilities of the instrument as to variety of voicing, and gives rise to that sameness from which you easily escape in a well-voiced harmonium. The little mechanical appliances of foot swell and the little fan working as a tremblant constitute the only escape which the instrument offers from monotonous voicing, which, in course of time, will fall on the ear of the best-constituted musician. A little word as to the exhaust bellov.-s. Will Mr. Jones pay that ho over saw them in operation—tltnt is, a pair of bellows which, instead of sending the air through the chambers containing the reeds, actually creates a vacuum presumably below them through which air rushes from above? If he ever did, will he please describe the process? I am sceptical, and my reason fordeubting is that positively there is no necessity for the process; the reed of tho American organ being as easily blown forward in the ordinary plan of any harmonium as thecnirminn concertina or harmonium reed. On this point I would beg the testimony of those English makers who are making American organs, notably Messrs. Cramer & Co., or any of your talented correspondents who are au fait to" the mysteries of the trade. Excuse me enlarging, I was led into these remarks through the snrprise expressed by Mr. Jones himself, that seeing the difference between the ono i nstrument and the other is so simple th at n o English maker should have originated it. In conclusion I do not want to expatiate on the merits of the harmonium per »e except I have occasion, bat I resent Mr. Jones's attack on it unless he had more to say in favour of tho American organ. Arc we not all agreed that the American organ is simply an harmoninm, in style, in reed, in bellows, in case? I do not despair of seeing added to any harmonium of sufficient size and

value a rank of reeds of the quality of tone of the " pure and true " description vaunted by Mr. Jones;but they would not occupy a leading position in the instrument, but be merely secondary, giving a little more variety of voicing at the command of the performer, who seeks all sorts. Not a few dislike the quality, considering them as emasculated and squealing in the treble, although sweet enough in the bass, as I have before borne my testimony. Mark Ellor.

THE HARMONIUM.

1:188] Sib,—Will Mr.Hermann Smith, " Eleve," the "H. U.," or any other fellow reader of the English Mechanic, help a poor man whose aspirations are larger than his moans, by telling him what is tho propor size for tho bellows of an harmonium which is to have eight sots of reeds? Also, how much larger they mnst be if required to supply ten sets? It is intended to build tho instrument with two manuals and pedals, so any information concerning matters of detail will be very acceptable.

The inquirer would be glad to be advised if it would be preferable to have two bellows, one for tho reeds connected with the lower row of keys, and the other (with expression) for tho reeds connected with the upper keys. Also, if it would bo preferable to make the pans thicker at the bass end, so as to make the wind channels longer. Mr. H. Smith says that a reed for 10ft. tone having a wind channel about half a yard long, yields the best tone, and possessing plenty of that cheap article, wood (not iu my head, I hope), and a.* I can use joiner's tools tolerably. I am quite willing to make the pans of any dimensions which will produce the most pleasing quality of sound. I do not, iu the least, mind tho labour of making the case of the instrument tall, wide, and deep enough to admit as large pans and bellows, or even two or three of the latter, if preferable, as may be considered best, so in any advice my fellow readers may be kind enough to give me they need not be restricted by consideration of tho space which can be afforded for the instrument to stand in. I am well aware that I propose to construct what would be considered a large instrument, although not "Alexandre's " monster harmonium of the future, but then I have been accustomed to play on a large organ. A Poor Organist.

HARMONIUM.—REPLIES TO QUERIES.

[384] Sir,—New subscribers who are interested in the harmonium would find their advantage in purchasing the back numbers which contain my treatise. Questions they have asked, and many others which no doubt will arise to puzzle them, have already been answered in tho progressive course of chapters explaining the construction and theory of the instrument. I made this reference to the past for the sake of tlioso who do not seem to bo aware of what has been done iu the direction iu which they aro seeking information.*

"W. A. S." (4538, page- 527) will find particulars of sound-board construction in No. 110: also details of Bizes and scales of channels in my last chapter, in No. 284, and of pallet and reed apertures in the forthcoming chapter.

"A Young Amateur" (3098, page 287) is referred to No. 109 for information concerning the '* Full Organ Movement," and its adjustment.

J. T. Hill (4487, page 550) renews a question often asked before, and which I have more than once repUed to, and also commented upon incidentally in tho course of the treatise in No. 133 aud others; likewise in letters. For his benefit I repeat the explanation of the defect he mention* as belonging to his own instrument. The Blowness of speech in the lowest octavo of the bass may be caused by the reed* not being properly set or voiced; they may very probably be set too high, and it is only when the force of the current of air becomes strong that they are drawn into movement or vibration; they should, therefore, bo pressed lower down that they will be set almost level with the block, the tip of the tongue rising perhaps l-16in., but the exact distance must be determined by experiment, as the character of the reed decides the treatment it should receive. If it is set too low, the reed is equally liable to sluggishness of speech, from an opposite cause, there not being sufficient strength of current passing under or at sides of the tongue to draw tho tongue with it, and the tongue acts as a door shutting its own channel. For this reason the large bass reeds are often reduced in width near their tips to secure a constant space at tlie sides for the passage of a current sufficient to throw the reed into action.

There is another cause for the slowness of speech .' n bass reeds of quite a different character—tho shallownessof tho body of air immediately under the reeds. The sound-board being thickest at the bass end there remainH but very little space between it and the valveboard, in fact, very often under strong wind and energetic playing the reeds will strike the valve-board. As heavy swimmers require deep water to swim in, as large birds find difficulty in rising until they get a good depth of air nnder their wing, so in an analogous mode these bass reeds need a bnlk of buoyant matter under them before they can gain their full swing, they require the co-operating elasticity of a mass of air to sustain and return the impulse* of vibratory activity. It is as hard for bass reeds to get up speed in tho open as it is for our legs to make progress over loose

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shingle—we want resistance to enable us to utilize our muscular force. Treble reeds may be easily sounded without being enclosed, but bass reeds require a body of air to strike upon in order to render their slow stroke effective, else the air gets out of their way too soon. On the other hand it is of the utmost importance that the air should not suffer great compression, the reed cannot swing freely when the air particles crowd thickly npon it. The slow speech of the bass is chiefly owing to this, that the air is packed iu a narrow wedge-like space trying to get through the reeds, yet pressed upon by the greater volume rushing from the wider end of the chamber, which exercises a dead lock pressuro disabling the reed from striking. To remedy this, to gain a play of elasticity to aid the reed to vibration, we make an artificial outlet causing the air to yield, yet not allowing it to escape. Drill two holes through the side or end of the frame of tho pan or sound-board, from 2m. to 4in. apart, and about jin. diameter or less, if need be, but near the end where the bass reeds lie. Over these holes on tho outside of the pan or sound-board glue a strip of soft sound leather from bin. to 8in. long, and 2in. or Sin. wide, so adjusted that it shall form a pouch or cheek. In this pouch the overstress of wind expands itself, and the additional bulk of air stored in this reservoir affords its aid of elasticity to return and sustain the impetus of tho reed.

In suggesting to the reader a reference to back numbers, I trust it will not be supposed that I am disinclined to the trouble of replying to now comers. It ia a pleasure to me to give freely of whatever knowledge I possess in the field in which I dig and delve.

HumiANN Smith.

CARBONIC ACID GAS AND OXYGEN.—TO
"URBAN."

[385] Sin,—I am rather surprised to find the statement I made regarding the effects of carbonic acid so severely criticised by your learned correspondent "Urban " (343) p. 592. In the first place I would inform "Urban " that I am not an " Exhibitioner at the Royal College of Chemistry," as he has pleased to term me, and if he looks nioro carefnlly at tho number he quotes from he will see his mistake. The contempt with which "Urban" speaks of little books, shows beyond, doubt that he never stooped to read anything so elementary as to be contained in such diminutive nothings. I did not profess to quote the exact words of Professor Huxley, but for the edification of your correspondent take the following from page 113 of Huxley's "' little book" on Elementary Physiology:— "The directly poisonous effect of carbonic acid, on the other baud, has been very much exaggerated, A very large quantity (10 to 15 or 20 per cent.) may be contained in air, without producing any very serious immediate effect, if the quantity of oxygen be simultanoously increased." My use of the word proportion may be called in question as being indefinite, or at least to convey an idea different to the quotation made.

"Urban" seems to have a wholesome dislike for indefinite statements, and this speaks well for his mathematical training; this being the case. I will endeavour to place before him in plain figures what I mean by increasing the oxygen in a like proportion. Take for example 100 litres of common air at 50° C. and 7t>0 mean pressure; this air consists, in round numbers, of 21 parts by volume of oxygen to 79 parts of nitrogen. Now, suppose 20 litres of this air to be replaced by 20 litres of carbonic acid gas at tho same temperature and

21 pressure, then ,-^r x 20 = 4 1-5 is the amount of oxygen replaced by carbonic acid. To make good this loss of oxygen, we must remove 41-5 litres of nitrogen from tho 1*00 litres of mixed gases, and introduce 4 1-5 litres of oxygen. In this way we have inado carbonic acid take the place of an equal volume of nitrogen in the air, and assuming the non-poisonous nature of carbonic acid when in small quantities, there does not seem to be any reason to doubt the statement made by Huxley. For the sake of simplicity I have supposed the nitrogen removed, although it may not be practicable. I cannot imagine where " Urban" finds his thousands per cent, certainly I have not introduced anything of the kind in the foregoing calculation; perhaps while "Urban" enforces definite statements, it will be well for him to make his own a little less ambiguous. Would " Urban" be kind enough to inform your readers, myself included, whether the experiment has been made of breathing air in which the whole of tho nitrogen was replaced by carbonic acid? I would expect the result to be the same as Dr. Taylor's case.

Since the function of breathing is in great part the removal of carbonic acid and water, to take iu at each inspiration a quantity of the gas of which it is necessary to rid ourselves must necessitate an enormous amount of labour to be thrown on the organs connected with this function, and should these organs prove unequal to the task death must ensue.

The statement that 4 per cent, of the gas did not produce any apparent effects on Dr. Smith is no doubt true, but he may be a strong, healthy man, and loss susceptible than the majority of people. The condition of the lungs would very materially affect the question, and to establish a rule on one individual example would not, I think, be altogther advisable.

With the ambiguity of certain of Professor Huxley's statements I have not to deal, bat I may say that few men have done so mu.h to advance the can-*.of true science as he has. His election as president of the liritiflh Association show? that ho has tho esteem of many of onr greatest scientific men.

Exhibitioner At Royal College Of Scienc :\

БОЛТ BUILDING.

[38G] Sib,—I send yon a description, with illustrations, of a boat I made for myself, which is both swift and light. It weigh» scarcely 501b., and is easily carried from the water to its house. Procure two pieces of pine, |in. thick by Sin. wide, which, when joined in the middle, make a keel 30ft. in length, Fig. 1. S»t this npon its edge, and for about 5ft. at each end round it on the bottom, Fig. 2, to fit the skin, or outside of the boat. Make the braces, Fig. 8, $in. thick and of a width abont 1 liu. in the widest part, tapering both ways, until no brace is required. Two braces are made different from these, of lin. thick, and of pine, seo Fig. 4. The one nearest the bow, placed lHiu. from the middle of the boat, the other about SOin. The depth of the boat and of these brace» was about 5in.t except at the ends of the boat, where they can taper to Sin. The two braces, Fig. 4, measured from A to B,

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Be careful in "turning," as you are liablo to strain the boat, to prevent which the planks were put in the bottom, as well as to rest the feet on. It is as well tu wear loose boots or shoes, so that in the event of going over you slip your feet out of your boots, which are apt to stick fast when placed under the strap on the foot board. A, Fig. 9. The V piece above mentioned should be well secured down to the waterproof cloth. In fact, it is as well to have pieces of wood underneath the cloth and fastened through. A boat of this description will cost about £i. Aquaticus.

Din., but from Anp to C, 6in. Next procure somo cedar plank, planed veri' thin; this cnt into lengths to make the planking of the boat. It is sometimes bent on "whole," except at the ends, but not being an extraordinarily expert carpenter I did not attempt this, which is the method of the Thames and Tyno boat-builders. Break joints, from D to E, Fig. 5, two full lengths on both sides, the ends being pierced. Soak tho cedar for about an hour, and in the mean time secure tho keel firmly to some flat surface, keeping it down by a piece of wood, Fig. 6, nailed to the floor or bed. Place the braces in the positions they are to occupy, aud^get two pieces of yellow pine about 20ft. long, Jin. thick, 2in. wide, and tapering to both ends. These must be rounded for about half the breadth on the outside, and be let into the braces and firmly secured to them and the keel, forming an even rounded bottom. Now put on the previously soaked cedar, bending it carefully to the shape, and fastening with brass screws or copper tacks. Cover the seams with thin sheet zinc or brass, fastening it with copper tacks; and clamp a piece of the same metal over each end to prevent breaking at the point.

The boat is now complete except the top, the cockpit B, Fig. 5, seat, rowlocks or outriggers, and sculls. On the top of the braces, all around the boat, fasten a thin strip of wood, and on the braces, Fig. 4, let this strip lit into the shoulder, A. Then put on like strips edgewise, from G to C, and from H to C, gradually thinning to the ends, Fig. 5. Cover the whole of the top with waterproof cloth or linen, tacking it to those strips and to those round the edges of the boat. Cover the taekheads with a small bead. Now the boat is entirely closed in, except where the rower is to be seated. Let the seat be fastened to the keel, and to the sides by brass screws.

The cockpit i3 made by fitting the clapboards for siding) around the braces, Fig. 4. At the end towards the bow fit two pieces to run out about 2ft. before meeting, like a Y, and at the stern the pieces may be formed in a graceful scroll; but a piece about 2in. high should be fitted to the after brace of the cockpit to prevent the water coming in when "backing." The V piece at the bow should be so fitted as to form an acute angle with the forepart of the boat, as seen in Fig. 7. The irons, or outriggers, are 4ft. tiin. apart across tho boat; and at their outside*, at bottom, about 14in. from the water. The irons are made as shown in Fig. 8, A being the rowlock with catgut fastened at the top to prevent the scull coming out.

Another piece of wood, shaped like Fig. 9, about lin. thick, must be cut so as to fit over the keel, and is secured by movable screws through the clapboards at the side, and Ъу a little block of wood fastened to the bottom plank and the side of the keel. ТЫ- is tho footboard, and is made to shift to suit the leugth of the rower's legs. It is as well to fit strips of sheet zinc where the heels come, to prevent the wearing of the plank. The boat must now be varnished, tho inside of the cockpit as well. In fact, it is better to varnish the whole interior before putting on the waterproof cloth. A pair of light sculls, well leathered at the button, and a small eusliion staffed with horsehair will complete the equipment. I muy as well mention that there is no necessity for the stem to be cut to the shape represented in the engraving, and the extreme ends of the keel should of course bo bevelled off to a thin edge. When going out for the first row, get some one to hold the boat steady till you are seated, and with sculls in position. There is little danger of tipping over when in motion, but when resting don't let go of the sculls, as by keeping them under the water or ou the surface you can balance your bout.

WHAT WE OWE TO THE ALCHEMISTS.

[387] Sir,—The labours of tho alchemists were popularly supposed to be diabolical, and the popular legend of

tho D (something) and Dr. Faustus, is a not much

exaggerated exposition of the light in which popular prejudice viewed their often useful works; but in this case, as in many others, good came out of iuppoeed evil, and while trying to find the philosopher's stone (his wooden block would often bo much easier to find, it being patent) the alchemists did find many useful things. I may especially mention antimony, which (however injurious to monks Paracelsus may have found it to be daring his experiments on their corpore vili) has been of great utility to us secular individuals, especially those of us who have the privilege of dining at the Mansion House with the Lord Mayor, for this indulgence creates a great demand for antimonial wine to counteract the evil effects of certain other bad wines then und there taken into the human stomach.

Another of tho alchemists' diacoveries, phosphorus, has (although we make light of it) come into extensive use during the writer's time. Those who, like him, can remember the flint and steel of old, which, although an admitted improvement on his ancestors' two firesticks rubbed together, was what with knocked lamckle^, blunt-edged flints and damp tinder—one of the torments of this life ia the cold dark winter mornings, —I say they will bless tho discoverer of the fact that much more light is to be got out of our bones than some of our brains are able to yield. Phosphorus lias an evil reputation for poisoning those who work it, but hero Alchemy's legitimate daughter, Chemistry, steps in and produces the perfect cure, or rather preventative, in the form of amorphous phosphorus, which surpasses poor human intelligence, inasmuch as it affords " in stautau eon s light" (moro than human intelligence often can do) without injnry to health or dauger to property by accidental fire, fordo not all its matches " light only on the box "?

Much as I am opposed to excessive governmental interference with what is termed the liberty of tho subject—a thing which often subjects other subjects to great liberties—when I consider how detrimental to health, and how incendiarily dangerous ordinary phosphorns matches are, I really think any government deserving tho name of paternal would be justified in restricting the liberty of mischief in its subjects, so far as to prohibit their production. This would, by the mere saving of the present loss of property by fire, bo a pecuniary gain to ns, not to mention the saving of life which would result. Perhaps it is quite useless to advert to saving life, for it is quite obvious that so long as Christian peoples go to war with each other, any argument in favour of saving life wonld be quite lost on them, unless it took the form of saving the lives of their own military men to kill others ; it might, however, have some influence ou a neutral Briton like the writer, who don't want to kill anybody, and who also, having an eye to tho main chance, might appreciate that reduction of the premiums on his fire insurance which would result. This argument comes homo to his feelings—I mean his breeches' pocket—but it's all the same.

An exceedingly interesting and instructive history of the various useful things discovered by those muchabused and misunderstood philosophers, the alchemists, might be written to advantage, and I do hope, even if you, Mr. Editor, cannot at present afford space for this history, that when the English Mechanic is enlarged eight pagos (the doing of which is now a matter entirely in the hands of its readers), some one of my fellow correspondents, more tit than myself, will be found both able and willing to write it for tho edification of his fellow readers,—may I add, also, for the edification of the readers of some other jouruals, which have occasionally boon known to borrow the matter of the English Mechanic, sometimes with, ofteuer without, acknowledgment. Perhaps, like the American re-publishers of English literature, they forgot, or considered quite obsolete, that old-fashioned commandment, "Thou shalt not steal."

The Harmonious Blacksmith.

rods, whose weight is far greater than is needful for a genuine suspension wheel, to carry a single rider; but pcrliaps I may be mistaken in classing it with suspension wheels proper, for Mr. Ту demon says its rods are "quite slack."

On referring to my former communication it will be seen that I expressed no doubt of the efficiency of the Phantom as a drivimj wheel for a lightly-loaded carriage. Sooth to say, there can be no doubt of its efficiency, when we are told that it is of small diameter compared with the Spider, and that it has thirty-two steel rods 3-lGin. diameter. They mnst indeed be rigid enough —unless extremely slack—to transmit any driving force required to propel a bicycle even up Highgatell 111. When it is considered that Smith and Houghton's No. 24 steel wire (pianoforte gauge» has stood at concert pitch for more than two years, with a vibrating length of ¿it>iu.—which fact I state on the authority of Mr. Chew; that the said wire is only l-20in. diameter (this is equivalent to loading the said wire with a force oí about 8001b.); that the rods of the Phantom wheel are about 2-10in., i.e., four times the diameter of No. 24 wire; consequently, if mode of equally good steel, capable of supporting sixteen times the weight that wire can sustain; that there are thirty-two such rods; that at least ten of them, from their nearly vertical position, are constantly helping to support the weight of the rider,—I again say, when all these facts are taken into consideration, that I believe any impartial judge will admit that the thirty-two rods in the Pbantoœ wheel have a tensile strength pretty considerably ia excess of that required to »tupend (I mean his weight, not himself) the very broadest of broad churchmen. In fact, assuming the average weight of the heavy Christians who ride on bicycles to be fourteen stones— which is probably an excessive assumption—the ten rods at least, always in action, would suspend at least a score of such heavy-sterned Christians, who might find it rather difficult to ride together on one bicycle, for the same reason John Chinaman gave when he evacuated hie fortifications, viz., "no tira piece man one place can be same time."

The number and weight of the thirty-two rods of a Phantom wheel being so enormously in excess of the requirement of any weight which can be carried on л bicycle, we havo a perfect right to inquire why the said wheel is mode so much heavier than is needed to support that weight. I have a very strong suspicion that I could indicate the reason its makers so construct it; but of this anon.

In reply to Mr. Dawson, I never did say Phantom wheels were not rigid enough for driving light carriages; whether they be made sufficiently so or not is merely a question of the proportion of the lengths, the thicknesses, and let me add, the degree of tension to which their steel rods are subjected. The rigidity of their rods increases, with increase of tension, but then the more tension you subject them to the smaller th« proportion of their tensile strength which remains and is avouable for supporting the weight carried; this, however, is of little importance when, as in the Phantom, the material employed is so greatly in excess of that required to sustain the load.

Mr. Tydeman says his Spider and the Phantom aro not to be considered " one und the same." (Juite true. Sharks and sprats are not exactly "one and the same," but—I trust the reader will not deem my illustration ßehy in the evil sense—they most decidedly have a common (piscatorial) nature, so also have these two varieties of the щтреш'шп wheel a common nature, however different the ¡rruportioiu of the parts of each. As in the instance of that msnotonous mûrirai (?) instrument which is said to be employed in the religious ceremonies of that little-known South African tribe, the Kanoodledums, the difference between the Spider and the Phantom and the difference between the long tomtom and the rhort tom-tom are only differences of proportion, both tome are essentially tom-toms, both wheels are essentially suspension wheels, unless indeed, the excessively thick laud »tack) rods of the Phantom act as veritable rigid spokes or levers, and ta some extent remove it from the class of wheels which support their loads on that principle.

May I just remind Mr. Tydeman I never asserted that the employment of elastic spokes prevented all the driving force from being transmitted to the rim oS the wheel? As well might I have said that when л weight is lifted by an elastic cord the hand docs sot lift the whole of that weight. What I did say was that if the spokes be elastic levers you must toed them before they can transmit the driving force, which is jast as true as that, in the case of the elastic cord, you must ttretch it before it can lift the weight. I with pleasnru add that I believe Mr. Tydeman's theory of the indiarnbber tire to be perfectly correct, indeed it песеььаriallv follows from the law that action and re-action are = each other. The Hakmonxous Blacksmith.

SUSPENSION WHEELS: THE PHANTOM AND OTHERS.

[388] Sib,—When adverting to a defect—for some purposes—common to all suspension wheels, viz., thnt their naves must to some (varying) extent be moved before their rims can be moved, which, by the way, is not a defect of much importance in bicycles and other carriages for light loads, I little thought what a nest of horuets (who have attempted to stieg me) I should disturb; but as yet my rather pachydermatous cuticle is unconscious of their penetration,—like most of my fellow Britons, I don't know when I am whopped. Let me add that in writing about suspension wheel» generally, ami the Phantom wheel iu particular, I was actuated by no hostile feeling towards its makers. It may, for anything to the contrary I know, be by far tho best wheel out, but it seems to me to hare steel

GERM DISEASES.

[S8ÍÍ] Sie,—I am much pleased with Professor Tyndall's paper on filtered air and germ diseases in Nos. 265, *2tío. To destroy these germs and cause of disease :—In all places of closeness, bad smells, or contagion, secure an inlet of fresh air, and then generate pure nitric fumes from dry nitre and clean sulphuric acid aided by warmth. These fumes are diffused all over the room, and seizing all the moisture and genus, become visible as a slight fog. Fan or blow the fumes into every crevice aud recess, und shake all clothing and bedding well in the fumes; every fresh article to be fumed before giving it to the patient, and every thing taken from him is to bo fumed.

In a hopeless case of putrid fever, where one patient

L just died, I recommended this process, and the
, ; ii. .-.irv carried it through most admirably, and
>t^ier patient begun to mend the very day ho iutro-
:*etl it and gradually became well.
C liis occurred soon after its promulgation by Dr.
r-ruiebael Smith, to whom the government gave
,OOU for so doing. The doctor, though zealous for
a public good, was not chemist enough to sue the
i r-ruling superiority of nitric acid fumes, for all the
ttars are hurtful to our lungs. The nitric acid and
r atmosphere aro of tho same gases; nitrogen 4 to
>x,ygeu; the acid 4 oxygen to 1 nitrogen; so when
ich diluted they are not hurtful but are rather

. * -nut, and yet strong enough to destroy all con_- - Ouh matter, and Bo render it safe for nurses and ■*itors. Cornelius Varley.

X*.S.—If these materials were kept at all hospitals

small parcels, quite ready for use when any patient ■irived, he might be fumigated, aud also the coniyance veil fumed; this would remove all objections » the use of cabs.

HINTS TO CORRESPONDENTS.

1390} Sib,—In No. 281, you inserted a letter (190) *oin ma on •' Several Matters." Not having seen any of ie "Harmonious Blacksmith's" lucubrations since, . lias struck me that I might have offeuded him. I hope ot. I wanted to see him purify his style and not to cease writing altogether. I beg now to offer one or two more lints to correspondents. Every one, I should think, ii it it admire the orderly manner in which the contents >f the English Mechanic are now arranged. I wish Aiough that correspondents wonld attend to the simple instructions you have given under "Letters to the Editor.' Von Bay M in order to facilitate reference correspondents, when speaking of any letter previously inserted, will oblige by mentioning the number of the letter." If this rule were strictly adhered to time would frequently be saved by those who wish to refer to previously inserted correspondence. It would entail little or no additional lubour on the writer, and confer a favour on the reader. There is another matter well worth attending to. As a rule the letters are answered by letters, and answers to queries appear in regular order in their proper department. But some correspondents answer a batch of queries iu a letter. Take, for instance, Geo. E. Davis. In the number just received, 1. 831, p. 590, Mr. Dans answers no less than eleven queries. Now possibly some who asked the queries may look for the answers in their proper place and may not think or choose to look through the whole of the correspondence for answers. It is the same with several other correspondents. See "W. E. D.," "Psi," and "Urban." In Mr. Davi&'s letter tho names of the query with the numbers are given. It is not so with our able correspondent "Urban," or even with " F.R.A.S." These gentlemen answer queries in connection with their pet sciences in letters ; but how, let me ask, can their valuable answers he recorded in an index? And this is the point I am particularly driving at. A new subscriber turns over the pages of some back numbers and he sees just such a question as he should have sent himself. He refers to the corresponding number under M Answers to Queries" and it is not there, and he refers to the index and there is no record. If the answer had gone in according to the subscribed form no difficulty would have arisen. I am not finding fault —far from it. Doing the thing orderly would not entail more labour, aud it would materially expedite reference. Let ns all endeavour not only to extend the circulation of our Enolxbh Mechanic, but to make it as useful as possible. Suburban.

real or supposed, in three positions—on, above, and
below. There are three styles of writing; the learner's,
corresponding, and the reporter's; each one differing
from the other. In addition to this thero are a vast
number of signs, termed grammalogues, arbitrarily
chosen to represent words of frequent occurrence. I
use the word arbitrary because they follow no rule,
and it is here that I take exception to the title " Phono-
graphy." It does not write by sound, because part of a
word cannot be the whole of it. It depends for success
on extreme abbreviation, taking care never to let one
sign stand for more than one word. What is not
simple is not possible. On this ground alone, Mr.
Grierson, who so ably defends Lewis, has the advantage.
It should be borue in miud that the acquisition of
shorthand depends more ou the individual than on the
system. The late Charles Dickens was a facile and
rapid writer of Mason's, better known as Guruey's,
By stein, published in the 17th century, and having little
merit to recommend it. The task of learning tho
simplest shorthand is one of immense difficulty, and
can only be mastered by constant and unvarying
practice. For all general purposes a system of abre-
viated writing, based on the common letters, combined
with judicious abbreviation, would be found far easier
of attainment, quite as effective, and more readable,
because more familiar to the hand and to the eye.

W. Cannabe.
[Want of space compels us to omit letters by
"Pegasus," Geo. Stedhan, and "J. H. It.," on this sub-
ject. Each of these writers answers Mr. Grierson, and
vindicates Mr. Pitman's system.—En.]

TEA FOR THE MILLION.

[392] Sir,—Many of your subscribers may be glad to know that the rasp berry-leaf—I mean the second leaf (that now on the branchos) makes the finest tea I ever tasted. The spring leaves are too strong. I have used this tea myself for twelve mouths at a time without any fault being found with it, Tho leaves, whou dry, should be infused just in tho same manner as ordinary leaves. Tho garden raspberry will do, but I prefer the wild variety, which is very plentiful in tho woods and dingles of England. Nab.

SHORTHAND. [391] Sib,—After reading the correspondence on shorthand in your valuable journal, most of your readers must be convinced that there is very little, if any, difference in actual practice between phonography and what Mr. Pitman calls the A B C systems of shorthand. The chief object of shorthand is brevity, and brevity is opposed to tho correct representations of sounds. The word phonography, as applied to shorthand, is a mienomer. By shorthand I mean the power to write as fast as we speak. Mr. Pitman says (page 521), "In the use of the consonants we are tolerably consistent." It is on the consonants that all shorthand writers depend. The vowels are always omitted. No one more strenuously insists on their omission than Mr. Pitman. If they are omitted, what is the difference between phonography and the A B C systems? If they are introduced and the systems are " correctly written," why is one not as readable as the other? It is the omission of the vowels that gives rise to the difficulty experienced in reading shorthand. In most of the shorthand works published during the last 20 yems, the authors have tried to remedy this defect by introducing the vowels in the line of writing—either written or implied. This is evident in " Sound Hand," by G. P. Reushaw; "Vowel Shorthand," by J. Rodam Carr; Thompson's "Phonography;" "Stenography," by A. Geiger; "Shorthand for Everybodv," by W. M. Williams; "Readable Shorthand," by Murdo Young; and " Universal Line Writing," by A. M. Bell. Some of these authors have been phonographers, and given it up on account of its complexity, and the extreme nicety and precision required in its notation. The care necessary in writing phonography mav be imagined when you are told the alphabet contains forty letters, the straight lines having three sizes, thick and thin; the curves four sizes, thick and thin. Hooks of two sizes to signify the addition of I, r, /, and the tenmnatiou Hon with loop* and circles of two ^izes for t $trt Ac. The system is written on a line,

METEORIC STONES.
[393] Sib,—The question of one of your correspon-
dents (" D. W.") as to the composition and origin of
meteorites is the more interesting from the knowledge
we now possess, through the spectroscope, of the surface
of the sun.

I have not had an opportunity of examin-
ing any of those meteoric Hony masses,
containing, as said, 6 per cent, of organic
matter, of a kind of black mould of carbon,
oxygen and hydrogen, somewhat like peat;
but in my neighbourhood, on one of tho
Southdown chalk hills, the summit of which
is capped with a patch of plastic clay, the
metallic meteorites are found almost on
the surface; the points and edges of the
crystals being quite perfect. One of these
masses, weighing about £lb., encloses a
portion of an echinus. Near this locality
is a gravel bed full of small fragments of
meteoric iron much rolled. Quantities of
this substance mixed with nickel are found
in almost every strata down to the lias, if
not lower. None of the portions found in
the plastic clay influence the magnetic
needle.

As to their origin, a friend suggested some months ago that these metallic substances were the ashes or residuum of the gas seen in combustion around the sun; he was the first who propounded this theory. It wonld account for the presence of these peculiar masses in so many strata of the earth ; the same process going on at the earliest geological period as at present, the 3 solid mass of metal falling, according to s§ weight, the shallower or the deeper, into tho semi-fluid strata. ~ ,__

Can that black kind of mould referred to above after nil, the black oxide of iron?

Laplace's opinion was that meteoric stones were projected from the moon into the confines of the earth's attraction, and consequently fell to the earth aud became a part of it. J. W. A.

THE SCREW PROPELLER AND ITS ACTION. [394] Sir,—The Rev. E. Kernan writing in your columns on "Elementary Science," has given a description of the screw propeller and its action, all of which is somewhat loose, but the paragraph referring to "Negative Slip "is especially incorrect.

He says "negative Slip (the italics are his own) is when the vesBelis going quicker than the ' pitch' of the propeller requires, t.*., when the ship advances at each turn over a space greater th-an the pitch. Suppose the Great Eastern to advance 40ft. at each revolution of the screw (its pitch being previously stated at 37ft.) this Htate of things i3 called the ' Negative Slip.*" Now this explanation is literally very misleading and the meaning intended to be conveyed is quite erroneous.

He continues—"And so far from being useful, the propeller is only retarding the progress. When, therefore, ■ Negative Slip' is discovered it is time to stop engines, their action is sure waste." This is worse than incorrect, it is utter rubbish.

Then he adds—" It is evident that some external force, wind, current, &c., is able to do more just now for the ship than the propeller."

This also is quite wrong but it enables one to see that Mr. Kernan, writing on the subject not easy even to the professional mind, has at the outset quite misconceived the nature of the phenomenon he has endeavoured to describe.

Tho somewhat singular result known as the Negative slip of the screw propeller, is said to occur only when the excess of the vessel's speed over the speed theoretically due t* it from tho screw cannot be accounted /or by " winds, currents, Ac."

The effect of stopping the engines as recommended by Mr. Kernan would be to Hop the ship aUo, and this plainly enough indicates that although the ship is advancing faster than the screw yet this advance is caused by tho engine, although not directly, in the usual manner by the rotation of the screw.

The effect of a strong favourable wind on a screwship would bo to assist the engines; and no doubt, if the wind were strong enough to force the ship ahead faster than the advance dne to the rotation of her screw, the screw would exert a retarding influence. But it is not conceivable how a current could have any such effect. Nor would this advance be negative slip.

Mr. Kernan also mentions a peculiar arrangement of sever;il boats driven by one steamboat. A system somewhat similar to this was I know tried on the Mersey some years since, but in this case the propelling barge was placed in front and [drew the train of barges after it like a locomotive. In the arrangement Mr. Kernan illustrates the propelling barge is placed behind and pushes.

There can be no question as to which is the better arrangement, and I fancy Mr. Kernan alludes probably to the system I here mention. W. H. N.

MEDALLION TURNING. [395] Sir,—As there was no mention in " The Lathe and its Uses " of medallion turning, and I see there have been many inquiries of late in your paper on the subject, I herewith send you a photo, of my little machine for turning them. It will turn one in 20 minute i which any other machiuo will take 4 or 5 hours to do. If yon think it would be a benefit to your readers, and particularly the amateur turners, you might insert it and the following, so that any amateur mechanic may make one for himself, as they can be applied to any lathe with two mandrels. A is a cast-iron stand ou which all tho slides, screws, wheels, pulleys, &c, aro fixed; B is a small pulley which drives the wheels C from the back, D are screws driven by wheels C, E are two slides moved by screws D on slides, E are three levers that turn in conical centres nud connected as

[graphic]

be,

shown to give motion from tracer to cutter, F and G are two tool boxes for holding cutting tool and tracing tool, H is a light spring to keep traces to medal. Both mandrels of lathe are made to revolve in same direction and same speed. An electrotype of medal is used for tracer to act on. J. L.

AN AMATEUR MICROSCOPICAL SOCIETY. [396] Sib,—With all due deference to "A. A. F." (342, p. 592) I cannot see the desirability of establishing another society when one already exists which is well able to meet the wants of those of our readers who are interested in microscopical science. Within the last few months freqnent mention has been made in our journal of the "Quekett Microscopical Club," a society that now numbers 500 members, aud which, for the small subscription of 10s., offers every advantage that one can desire. If "A. A. F." will refer to Vol. X., p. 241, he will get some insight into the practical working of the " Amatenr's Friend;" or by applying toithe secretary, 192, Piccadilly, he will soon learn that by enrolling himself as a member he will meet with eeery facility for prosecuting his favourite pursuit.

With reference to the inquiry of "E. L. G." (4615) as to the presence of fluorine in the human body, absence from home has prevented me sending a reply; the matter has, however, been so well gone into by three correspondents in this week's issue that it is unnecessary to say anything further upon the subject.

Beta.

[897] Sir,—lu reply to letter 342, in last issne of English Mechanic, 1 should like to remark that the society lately formed in Manchester, under the name of "English Mechanics' Scientinc and Mechanical Society," entertains the features mentioned in that letter.so that it would not require a new society to be formed. The object of Uli*, our society, being the instruction and mental recreation of its members by the reading and discussion of papers on Scientinc, Mechauical, and Literary subjects, as well as for promoting exehaugo of opinions on interesting subjects. We are not restricted to make mechanical investigations, as I believe is thought by many of your subscribers, but have, as will be seen from the above objects of the society, not excluded any scientific or interesting topic from our attention; therefore, I think "A. A. F.V suggestion for a separate society for microscopical studies needless.

A. Tolhauses, See.

REPLIES TO QUEBIES.

*„* In their answers, Correspondents are respectfully requested to mention in each instance tho title and number of the query asked.

13903.]— GRADUATION OF A CIRCLE.—On a strip of copper (tinned iron might answer) punch with a doubleended punch a number of holes, one in excess of division wanted; these must be punched by inserting one end of thepuueh, which should be rather larger than the other, into the previously-punched hole, und bo in ¡same straight line. The strip being thus prepared, turn down a circle of board to the size round which the strip will go ti^'iit with the two end holes covering, through which a pin may secure tho strip round the board, or the two end holes may bo riveted, and the strip forced on tight and secured. " This will form a division-plate for required circle.—Suffolk Amateur.

[SÜ19.J— GALVANIC BAND (unnoticed Query).—I can see no cause of failure in your correspondent's appliance or manufacture of the above. Ho must, however, only expect weak effect. I did not iiuLice this query, or should not have allowed it to pass so long unanswered, and have been from home.—StfFolk Амлтвиа.

[3049.]— GUAYANA.—Without admitting that Stleler, or any non-Iberian, is authority for Columbian names, I was certainly surprised at learning from "J. G." that his atlas anywhere reproduced our Guy in this name. I find it does so in the small-world maps uud the small South America, while the general map of both Americas bas the full syllable (Juay, and the detailed South America repents it four times, always Quay. Moreover, his other authority (and that an Englishman), "J. G." himself quotes as" beginning the natives' name with Quay and Wai! The fact is, that had men of our race discovered them, the spelling would unquestionably have been Wy anna. The doubled n would have insured the word against being made dactylic—if that is what *'J. G." means by "short"—and the two letters Wy would, in Knglish еуен, but no others in tho world, have served for all that the Latin races шеяп by G ¡Mi, the G beginning this and sooree of Spanish-American names by no stricter right than in the Latin forms ot Walter and William. The native tongues throughout both Americas abounded in the syllables we (or cons in Jonathan) exprese by Wo, Wha, Wy, and Why. Tbeso the Spaniards wrote Gttat Hua, Quai, and Huai, tho (/ and H being regarded as a kind of oppooites hi mutter of aspiration, liko the Greek 'a*d ; ' but one or the other being always required, in their eyes, to nail up tho н to the following letters as one syllable, and give it that strong еотопалШ quality that oar Gothic ancestors better Indicated by enlarging it into IP. It was for a like reason that they enlarged i, whtu it begins a syllable, into j ; and between two other vowels doubled it, as </, to express that the former t mergee into the previous syllable, while the latter becomes a semi-consonant beginningfthe next; and this y, by losing its dots became i/, as in this very name; so thai, though neither U wrong the spelling with у (or y) is more proper than with a single i. But the lact of our using single letters to expi ess diphthongs, as in by, bite, Bute, a thing undreamt of in any other language ; and that we might have expressed this syllable by Wy, can bo no excusef or corrupting Guai into Gut or Guy, which not only every foroiguoi, but nine-tenths of Englishmen would be led to sound like the first syllable of Guido, Gayón, or even of Guienne or Guinea. With regard to climate, nobody fancies any country within 10-4 of the line, or even 30е; is "healthy for Europeans," and the Cüíoniaf Guayanas are known to be signally the reverse. It was worth noting, therefore, that, on the other hand, Venezuela has less ill name on this score, and contains, perhaps, more European bluod, than any other intertropical country—certainly any under the 10-parallel. A friend, moreover, lately wont on foot, alone, and without a tent, across the 400 miles of Calabozo plains, from Caracas to the capital of Guayana; fording or swimming the minor streams. I do not supposu any each journey possible in the hitter province itself, but should like to know in what other tropical continent the like has been done?—E. L. G.

[4115.]—TROPICAL FIBRES.—I have just received the work about which "J. C. P." inquired several weeks ago—"Tropical Fibres, Ac," by J. G. Squter. I was quito astonished in seeing that this book, advertized among "new ones" in a paper, was printed in 18ПЗ; it contains only 64 pages of print and lti plates. Tbeso particulars may perhaps serve the querist.—Reknabdin. [4210.]— SIGN WHITING (Unnoticed Query). — if "Brush Hand" will buy along sable-haired writiui* pencil and a book of ornamental alphabets aud practise from them, noting well the form and manner of bh;uliug the letters I cannot see bat what be may soon bo master of tho art of sign writing.—Blackuubx.

[42JH.]— BREWING (Unnoticed Query).—Ales and beers left alone require a considerable time to bocome bright. If early maturity be required, X know no reason

why such finings as isinglass or white of egg should produce acidity. In my native village amid the Cliiltern Hills we never tapped our best ales until they had been brewed eighteen months. Those of my friends about Buvton-ou-Trent arrive at maturity in as many weeks. It is attributed to the water. "Only fancy it Burgundy, and 'tis worth ten guineas a quart." —boniface.

[4299.]—SILVERING CLOCK DIALS (Unnoticed Query).—Dissolve a piece of silver in dilute nitric acid (two parts acid, on о part water). When dissolved the liquid will be a blue colour if manufactured silver is used, as it contains copper; now place in the solution a piece of clean copper, when after a short time the silver will be thrown down as a grey powder. When there is no more deposit allow to settle, then carefully poor off the blue solution, and fill up with water so as to wash the powder from tbe acid, allow the powder to settle, then pour oil as before. Ropeat this two or three times, so as to wash away every trace of acid, when the powder may be left to dry. Now mix together equal part« of cream of tartar and common salt. Thoroughly clean the article to be silvered with tine emery cloth or paper, dip a piece of clean rag (previously moistened with water) first in the cream of tartar mixture, then in tbe silver powder, and apply to tho surface, rubbing until silvered. Be careful not to let tho lingers touch the article, wash in water, dry, when the dial may be varnished. Mustie varnish diluted with about hnlf Us bulk of spirit answers very well. I have just silvered eoiuo articles bv this means.—S. Moody.

P.S.—The following taken from p. 19, Vol. I., of the Ekolihh Mkcuanic would no doubt answer equally well but I have not tried it :—Nitrate of silver, 30grs,; common salt, 30grs. ; cream of tartar, í>¿ drs.; mix, moisten with water and applj.

[4300.] —SAUSAGES (Unnoticed Query).—For pork sausages, chop up fat and lean meat together, season with sage, pepper, salt, and allspice; 6oz. of bread crumbs to be chopped with 21b. of meat. Fill skins that have been well cleansed.

Polonia are mado of fat and loan pork, seasoned with salt, saltpetre, black pepper, and allspice. After standing several days with the above well rubbed in. cut small and mix with chopped shalot or uarlic; fill oxguts that have been thoroughly cleanied by scouring, salting, and soaking; hang up to smoke; the gut should be tied at intervals of six or eight inches, or less, us thought desirable.

Qx,'ord Наиаш?ел.—To a pound and a half of pork add the same quantity of veal, free from skin, Ac.; three quarters of a pound of beeí suet; then mix, and chop fine; add bread crumbs, season with dried sage, pepper, and salt.

B'tj 8аша#ея are mado in the same manner, but more highly seasoned with marjoram, thyme, and parsley.

Saceloys aro prepared of salt pork and beef, with onefourth part of bread crumbs, and a liberal allowance of spice, Ac. Boil for half an hour.

Mutton Баияадея.—Two-thirds of mutton to one-third of pork; tho seasoning should be more delicate than used for beef sausages.

French Sanxaae*.—Take pork, which mast have moro fat than lean, chop fine; also parsley and chives, pepper salt, and spices; either put in skins, or makeup into cakes and grill. Vary the flavour by adding truffles or mushrooms, instead of chives. From MSS. recipes in an old family collection.

For trade purposes these recipes aro often modified, by using oatmeal in large proportion, instead of bread crumbs, as pork sausages aro now selling at from 6d. to Is. 2d. per lb.—Paterfamilias.

[4317.]—COLOURING SIZE.—Use patent white size, about 2d. per lb.; and common ultramarine, about 6d. per lb. The yellow tint of common size will affect blue, or any delicate colour.—Derfla.

[4337.]—HOLLOW CANDLES.—I presume there is а glazed metal rod passed from top to bottom of each candió mould, with a hollow wick similar to that used for lamps, passed over it. When cold, tbe candle will draw out of the mould, and the rod out of the wick. The object is to brighten and spread tho flame of the candle. —derfla.

[4339.]—LA CROSSE (Unnoticed Query).—A short illustrated article, giving direction* as to the method of playing the above game, appeared in the tirst weekly

S art of Cassell's "Popular Educator'' (new edition, Го. 1, Vol. I.), pp. 15, 16. Your correspondent may obtain a copy of the above specified number through any bookseller.—S. ... it.

[4351.]—CASE FOR FERNS AND MOSS (Unnoticed Query).—From 8iu. to lün. aro good depths, according to the description of plants for which the caso is intended. It is better to have an apertaro at bottom, which after tho case ha* been planted and well watered should be plugged up. The case should be stout, of the best yellow deal, charring it inside would be beneficial, but avoid metallic linings. The '* Fern Garden," by Shirley Hibberd, contains many valuable suggestions and plans of cases.—H. В. M.

[4301.]—METHYLATED SPIRIT.—If "T. L. H." will forward the address of " the chemical factory where tinctures of all kinds are manufactured from methylated spirit," to tho Commissioners of Inland Revenue, ho will probably bear of something to his advantage. Bv the act 29 and 30 Victoria, chapter 64, section 8, it "is enacted, that " No person shall use methylated spirit or any derivative thereof in tho manufacture, composition, or preparation of any article whatsoever capable of being used either wholly or partially as a beverage or internally as a medicine," under а penalty of £100 and forfeiture. The ninth section also prohibits anv alteration being made in "finish," except by the addition ofgum, resin, or colouring matter, under a penalty of 1:200 and forfeiture. A ору of the above sections was furnished to every chemist and druggist in the United Kingdom upon th* passing of tbe Act in Äugest, 1в66. i leave "T. L. H." Lo draw his own Conclusion.—A REVENUE OiFlCKH.

[1307.] - RE-ENAMELLING- CLOCK DIAL.—" Sheffield Flood," p. 4S4, can ro-cnainel his clock dbil by grinding white lead with carriage varnUh, api>Iy it with a brush, dry it in an ovon wftii л gentle h*at, and polish with tine pumice. Tho figures aro painted with mustie varnish and lamp-Маек made thin with cither turpentine oroil of spike lavender.—J. M.

. /

[4372.]—OBOE (Unnoticed Query).—Not seeing wry reply to "Auon'e " inquiry, I beg to »ay the f»Alowinii :— That a first-class reed for the oboe generally costs about 2s. 641.. but as for tho blowing tbe instrument I еапьег help him, as I am nearly fast with my own. I may abo add that I think there are л good many oboes in tbe country, but that very fow are properly played. I should much like one of our friends of the Ex&Liñs Mechanic to give ue a few practical lessons. I think. they would be mnch appreciated.—Judas.

[4485.1— TO "GASHOLDER."—The gasholder mode by S. Highley, is dear I think for £1010s., yon cernid g*--. a gasholder made much cheaper. I will send plan rad size if required; the advantage is great, as you can ke*^ your oxygen for days without spoiling, which ia mur>than can be said for the bag plan; but if yon wish to travel from place to place, you would find the gasholder too bulky.—Operator.

[4004.]—ELLIPSES.—"J. K. P." surely doe* see that if the curve is "ever egg-shaped, it mast alwayeb*Tic symmetrical," but does not go so far аз to »ay witi. "E. L. G." (p. 595), that it is a "more eomplexeur^* than the ellipse, however long his connecting rod.4 Ii is not an *• oval of tho fourth order" at all, аз may tscon from its equation:

ji=2R + a-2 ^/Ra - ya - ,ya* - у* where 9 л ia length of connecting rod, and Л R isleatóof crank, and is no more complex than a c«V seetion. "E. L. G." is a great deal too critical un T. W. Boord's mere sketch of a trammel; Ыс ih^*. gentleman is quite equal to self-defence. As Cowçtr -. ellipsograph is priced£2 to£4 inHoltzapffel's calaba and n,s mine, which й shown on p. 480 (does this poi^: the charm of novelty for ** E. L. G." ?) woald ew double those amounts, according to sise and finish- L a draughtsman, requiring to strike ovals conetair,r something cheaper is a desideratum. If ** £. L. 0 will take the trouble to read my letter on p. 4W. ht? »i perceive that I was at least then aware of the Lx symmetrical nature of the curve produced, as I take the trouble of pointing out why one of the two ackeinej there proposed has an advantage over the other /or certain purposes; but I repeat that whea the length <»! connecting rod is five or six times that of crank, tb*j departure fromthe true figure is so slight as to be hardly perceptible, even when one oval is laid over the other: and, 1 suppose, amply accurate enough for striking thstmi-ovftls in isometricol drawing. In an iitstnimeumade on the connecting-rod principle, a pin might Ьь made to work accurately with acarc«Jy anything' additional in the way of inechanietd complication. And now, taking the first part of "E. L. G.V letter last: the fault of the subject being recurred t«i does not lío w\t,b those who set down to answer я query when it \e pa: forward, but rather with the person who asks it withou: referring to the back numbers. Also, tbe plan of etrikin^ ellipses with a cord, even if accurate, would be perfectly inadmissible on a drawing, though ¡t serves tiepurpose of the gardener for staking out a flower bei. in which also so much accuracy is not looked for.— J. K. P.

F4517-1—FISHING GUT may be stained with tea, coffee, or iuk-ftnd-water.—Suffolk Amateur.

[4541.1—EMBROIDERING MACHTXE.—The máchica referred to by "A Braider," is one sold by the Willc&> & Gibbfl Company. It makes a stitch like the Willct»* Л Gibbs sowing machine, but the embroidery íh on the upper side of the work, and the feed is controlled i>_v a small handle which enable« the embroidery to be doue in all directions without stopping or turning tho worit. The reel is on the under side, an! tho needle U similivr to a crochet hook.—Thos. Fletcheu.

I454Ö.J—DIVISION PLATE.—In reply to remark* Ъ> "J. K. P." I might, with great truthiuluess, begin m y reply in the same words as those used in your impression oí 2nd iu.-.t. by your worthy and very clever correspondent relerred to, but as I recommended no partícula numbers, and only gave such as my own experience finds useful, and also as I referred to a printed list .1 dividers by Baker, I will only explain, as briefly a* 1 can, what to your aforesaid correspondent must appear vcrv mysterious. My meaning oí dindes into different? j is, "that No. 720 Ьач 15 divisors, viz., 2, 3, 4, 5, fi, 8, 9, 3". 12,15, 16, IB, 20, 24, »Ö; 360 has only 14: eo that 72»i appears to be the greatest divider, and consequently the most useful number of all the other». As to the Nos. 330, 14Ï, 120, they will be found probably equally useful and necessity when "J. K. P." has to do flue work with poor eves. I fear that the experience of" J. K. P." in fine fluting, drilling, Äc, U not quite equal to the attention Ihave at times to give.as I have oft^x. found every No. on my division plato come in. I encîo*<> for "J. K. P.," a copy of Baker's "Ready Ъвскоъег. which I request him to keep for reference; ana **ry probably Mr. Baker may answer bis interrogatory a* "whoever had a circle of 720 on his dividing plate? *' I have not» but all tho other Nos. in the Ready Reckoner arc on ray Hultzapffel Rose Ençme Lathe-— W AH SR or.

[4540.]— DIVISION PLATE OF LATHE.-For ordinary ornamental turning, if the division plate only admits of throe circles of hole*, I should say that 1&), 144, and 112 would be found the best divisions; ISO divides by 2, 3, 4, 5, 6, 9,10, and 12 ; 1+4 by 2. 3, 4, 6, 6, 9. and tS . and 112 by 2, 4, 7, and 8. A fourth circle of 96, if «me could be found for it, will often bo useful. I hav« a lathe of HoUsapffel's containing the divisions recommended by " Wahsrof," viz., 221 and 209, and duriu« the twenty-eight years I have been working with it, I nave never onoe had occasion to use either of those dirisieos—G. С. C.

[4555.]—PHOTOGRAPHY.-"Lex" must say to «h^t size he wants to make his enlargements, and if by eobr or artificial light, then if tho editor will «pare me ro*>v I will give him full instructions drawn from mrvwo practice. To the second question I must say that it would take a column of the Mechanic to properly »«wer J it, but the formulie I use is this, whites of egg* "7*^Я beaten bva machiHefor a snfficient time to convert tk^t-^m to froth/thlfl is allowed to settle to a clear liquid, лпеЛ to each callón ¡ч added 800grains of chloride of ammouiaru. fctOO grain* of chloride of barium, dissolved in SOouxic«.:^ of water, the two well mixed, poured in flat dishes, atiO tho plain paper floated on it, for from 15 seconds t... three minutes then dried in a room heated to TO^. Tp,, free the bath from acetic acid, pour into au ovaporatiu _ . eva\K>rate to dryness, fuse the residue, dissolvo in *r to 30 grains per ounce, iiltcr and nuke just tr.il or slightly acid, with nitrie acid. The antotype tluH process is a method of printing ill carbon by

processor ol Swau and Johnson, the patents are , uy ft company who grant licenses to work the pro

on payment of a small sum per year.—Operator.

S5BO— TELEGRAPHY.—I am obliged to "Termi"for his reply to my query under the above heading,

uiuit confess my eiror (through hasty drawing) in ,iu±r two wires on one lusuliitor. I also thauk " John 4*," bat " Terminal's" reply is undoubtedly right, as ■iricity in any shnp*> would be as likely to strike the a a.'* tue " guard."—Mua.

oiG7.] MATHEMATICAL INSTRUMENTS- — 8. vt-n^ asks a question which week after week it baa Q my intention to ask, and although it is, so to

iU, a wrinkle of trade, yet among the numerous tl-heartcd contributors to the highly-valued English Oiianic, there are surely more than " J. K. P." who x and pleasure in offering advice aud giving instructs on this subject, clear, explicit, and practical, Likout doubt there are many besides, who will be very xtefol to any skilled brother who will, ia such a trit, reply to the following questions; or, in their Liai way. describe how the work is put in band and ii«. The sort of *l goer gathering " spirit, causes many our young folk to prize the heirloom instruments, lieh have a value iu their estimation above even the e finished foreign cases, but a bad or broken joint renr.-i iliL-in of no ube; the will to mend it is consequently ten strong if the way to do it were known. First, on. the joint-plates" of drawing instruments, if steel, «_* so soft that they can be sawn out, or the brazing reel', el and pulled out, or if worth while, a new joint .ii he made, aud screwed or soldered lower down the t*. Second, after the plates are prepared is there a icthod of fixing them with cold solder or brazing, or is

always by heat? If it is please describe the kind of irnnce, fire, or blowpipe used, tor there is such a risk [ running down the solid metal, which is often only a Lout wire of brass or white metal; aud what solder is >*ed? And last, while the tile must shape, is the finishng done with it? I have beard that it is done on the

lend lap," but how is that made, is it used dry or with il r The finishing is clearly seen to be across tho work udvery plaae aud even, and the small projections or lists re all sharp ent, so much so that the sharpest edge or ngle of a lead wheel, would seera unable to mako them. low thou is it done? A kind, practical, painstaking eply will be gratefully received by many amateur outfits, who in the darkening evenings will rejoice in rying their hands at this interesting work under good i -truclions, instead of being by failures and ignorance iscouraged from attemptiug to revive the appearance ,nd usefulness of their old instruments.—S. 11.

\ 1^68.] —WEIGHT OF RAILS.—" Ferruiu" seems to be ibie W easily ascertain the weight per yard of round, - juuro, or fiat bars of steel and iron, I suppose, by means >l the usual tables, lie asks a rule to find the weight per

Lard of rails of various sections (iron and steel); but ow can he expect that can be furnished him unless '.hi.' sectional area of each individual specified rail shown o>n tho tracings is given? If such were the case, he '"< uild of course by tho same tables, as .easily as in the former instance, learu their weights per.yard. A simple wny to find the weight of any section of rail he may receive is to get a carpenter to make from the tracing a

all-sized model of the rail 6in. long; sink it in a quart •f water, measure the displaced water, and check the

une by measurement of the emptied space in tbe iuart after the model has been taken out. Ascertaining [.bus the number.of cubic inches iu a length of 6iu., he Lias only to multiply by six for a yard, and by the weight

)i a cubic inch of steel or iron to gain the desired woight

H-j yard.—S. H.

[4573.]—GEOLOGICAL.—Tbo limestone beds which wo quarried on tbe west side of the Malvern Hills belong to the upper 6ilurian system, chiefly the Wenlock i ocks of thatiormation. Should " Philosopher" require rtiiy further information I shall be glad to give it.—A. D.

[4W9.]—TENDER FEET.—My plan is to wear shoes suificienUy roomy to admit an inner solo of cork or felt; tkick soles are preferable to thin ones ou country roads. On arriving at night soak the feet In warm salt and water. Next morning bathe them in cold water aud rub well with a hard brush. Forty years' experience have proved this practice- to suit.—Akolii Man.

[4590.]—TOWN GARDENING.—In tho centre of Loudon, amongst smoke and dirt, occupying tbe upper p.irt of a house, with a broad staircase lighted from nbove, I have, at about 10ft. from the skylight, arranged around the walls tbe undermentioned plants, which live and flourish luxuriantly: —Scarlet runner bean, Htliotropium Ptruvianum, Scoloprtulrium imlgare (hart's tongue fern), Btohnum $pieant (hard fern), Athyrium jllix fir-nitta (female fern), Otmnnda regalia (flowering fern), iJ.-TfrnwroruiM tcaber. Nasturtium (varieties), Mimulu* w/»c)i«(tw, Cobf-a itcamirtm, Geraniums selected for toliw* rutber than flower, Fuchsias \urious, I*ahpi* ni-\:vUi, Convolvulus major, Ly«imach<u nuiiimularia (moneywort), Suxij'raga Samunto/a (mother of thmsatidrtf, Vinea major (periwinklei, Tntdcscantia zeltrina; [jycupodium fvnuotfum, L. apodum, and L.dfntirulatum, under bell-ffUsses. These plants cost In the streets aud markets from Id. to Is. each. Tho compost I use is vegetable mould mixed with one-fourth part of iino white sand; pots, well drained by potsherds, and bits of charcoal. They aro well supplied with water, in which every fourth day is dissolved Joz. of sulphate of ammonia to each gallon. The pots stand in porous red stands, from which the surplus water is drawn off by a ei]ihoD. When any dirt appears on the leaves the plants are carefully sponged. Such a utilization of a staircatu might perhaps afford to others tho same pleasure it give* to—An Attic Wokker.

[4B5.]-HOtI8ES FROM STRAW, Etc.—Iu the

W.irk-iftQ Jfan, ft paper published by Casscll, some two years aj,'o, there was made mention of workmen's cottages beiag built of bundles of straw and some other material, t believe they were building near Twickenham, about Un miles from London.—Hi.ACKBraN.

[1805.]-PROPELLING VESSEL BY WINDMILL.— -* - I hsvo misled Mr. liurtou iu tho matter of tho uautical ivibduuU, I am only too giad to see that he is this week

put on the right tack by various correspondents. I am sure we should ali be very glad if John James (4605, replies to queries) would kindly give us some information as to the construction of his model, if he does not wish to l;eep his ideas private. If Mr. James could meet mo at any decent piece of water with his model, I think I could convince him that it would not go at ilouble the speed or a sailing boat. W. Habbouate.

[4616.]—PROBLEM.—In my last, I gave "Amicus" the algebraical method of solving tho statical problem. Tho printer or myself made two immaterial blunders—at least immaterial ao far that the veriest tyro could tell what was meant. Thus: in line 18, read A CD = 185not A t' U; and in 4tti line from the bottum read,

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-y2_

a 2 Z» - X* «/8 (^^

= 2rt- 1-414 x*
10,00a = i>8fl rs (multiplied both sides by lOoti)
10,000,0000 » (M6 *2

10,000,000 _ 5,000,000
586 2«3

z* =^/no04W, &c. = 130*6, Ac., Ac.

If the decimal places are carried further it will make a alight difference in the answer. P.S.—I shall be glad to solve a specimen example of such questions as can be worked arithmetically, in order to benefit those students prepaiug for the Matriculation, Loudon University, if the editor will spare space.—C H. W. B.

[4616.]—PROBLEMS.—If I understand well, the problem is:—One angle of a rhombus is 130 , corresponding diagonal 100, to find the side. I observe that the »upplementary angle is 45 , hence tho side is the radius of a circle circumscribed to an octagon, the tide of which is 100; seveval tables give for that radius 130*7.—Her

NAIIDIX.

[4624.]— PENDULUM SPRING.—TO "YOUNG JOBBER." Pallets and lever depths. The proper depth for escape-wheel teeth on the pallets is, that they fall just safely ou tbe locking face of each pallet stone, on no account must the depth be left shallower, because if the teeth when escaping from either pallet fall on the ilope the guard pins wUl be driven upon the edge of roller, by which the motion of the balance will be very much impeded, aud thereby prevent the watch keeping any regular time ; sometimes when the watch has a strong mainspring it may stop through such shallow locking, the guard-pin being forced against the edge of roller, thereby stopping the balance. Of course when set to the proper depth just named, tho depth must be transferred from the depth-tool to the upper plate for marking off, aud when uprighted in the framo the following is a sure method for trying these depths. The wheel aud pallets being in the frame, screw in the balance with the roller on, having previously caused the pallets to be end-bound, by placing upon the upper pivot of the pallets* staff a thin piece of cork. Next lead tho balance round to allow the tooth of the escape-wheel to fall on the pallet stone. Tho pallets' staff being end bound ensures a good view as to the amount of depth tho tooth has upon the stone. If the wheel be deeperouthe pallets than I have named, the unlocking will be effected with loss of power. One thing must bo always kept in view, namely, that the wheel teeth lock just over the rounded edge of the pallets' stones. Thus far the wheel depth on the pallets. The It vcr depth upon the roller and pin next follows. The roller-pin nhould have just visible freedom in tho lever notch, and at the moment of the wheel-teeth falling on the pallets—they being kept stationary by the piece of cork just referred to—tho corner of the lover-uolch should be presented to rollerpin, and then when holding tho balance firmly, at that point of its motion, with a piece of peg move the lever from side to side and observe what amount of'inotiou it has; if the same—or a trillo more than appeared when trying the size of the rollor-piu in tho notch—that is a good depth. If there be no shako till the balance is moved onward, then the depth is too deep aud the length of the notch must be shortenod. Always observing when setting tbe roller-pin and notch-depths that just half the pin is embraced by the lever-notch. I have omitted to state that the framo should be held in the left hand with the fore-finger upon tho balance for leading it, and that with a nicely cut pioco of peg force tbe escape-wheel onward. Tbe remaining portion of " Young Jobber's r' query respecting *■ the adjustment," that will be found in my article in tbe British and Foreign Mechanic, Vol. IL, p. 84 ; subject—" Tho Watch: Its History, and How to Repair it."—Seconds' Pbactiual Watchmaker.

[4030.]—COACH-PAINTING.—If an "Old Subscriber" will say what coach, carriage, or other conveyance it is that hehas to paint, I will do my best to give him all the information requisite, as there arc almost as many ways of painting a coach, &c, as there are days in the year. —Blackburn.

[4633.]— WEIGHT OF METALS.—I am sorry I had not time to reply to Ralph Williams before. To his first question I can only say that good works ou mensuration generally contain a chapter on specific gravity, which is what he wants. Huttou's " Mensuration" Is published by Longmans, London, and others; its price I don't know; I bought it second-hand. In reply to the other question, solid geometry proves that its sphere is § of its circumscribed cyliuder. Of this cylinder the diameter and height are equal, iu this case 7in. Therefore, T-* x *7H54 will give the area of the base,

which multiplied by the height 7, will give the soliditv, i.e., T* x -7854 x 7 = 7* * '7854 = the solidity of the cylinder, $of which will be the solidity of tbe sphere. Therefore, 7" x -7854 x j{ - 73 >■ '5236 = the solidity of the ball.—J. Nash.

[4647.] —PHOTOGRAPHIC—If "Mendicus" was making a bath for negatives the rain-v. ater will not do, he must add a few drops of a solution of carbonate of scda to the bath, just sutficeut t<> cause a * light precipitate, shake well and put it in a clear white glass bottle, and expose to full sunshine for two or three days, then filter carcfullv, and add a drop or two of pure nitric acid suJhcient to slightly redden blue htmns paper ; if made of proper strength, 35 grains per ounce, it will work jirtt-rat<. The fact that the objects on thegrouud gUss arc reversed, will mako no dificrence if he is taking negatives, the prints will be perfectly true to nature, it is owing to well-known optical laws, aud not to any fault in the apparatus, us he seems to imagine. Tho third question is a rather difficult one to answer, as he gives me no data to guide me. Does the piste reremain quite clear after the dovelopcr has been on it a short time 7 if soft is owing most likely to too short an exposure, or a too acid bath ; keep tho bath so that it just turns the colour of litmus. If the plate turns black or brown as soon Ub the developer is applied it is owing to fog, perhaps from white light iu the dark room. Prepare a plate and keep it in the dark room for about five minuted about I2in. from tbe window, then develop it: if it remains quite clear, and after fixing Is as transparent as the glass itself, the fog is owing to light in the camera or dark slide. Tho remedy is obvious. If it fogs prepare a plate at night, using a candle about a yard from tho plate to light the room, and develop as before; if it fogs, turn the bath out and proceed as directed for the bath made of rain-water. If that does not cure it he must ask again and send all particulars.—Operator.

[4647.] — PHOTOGRAPHIC—TO "MENDICUS."— First, your mixing the bath with soft filtered water will not in all probability affect tho working of it; try it, and if it should there is no remedy but to crystallize the nitrate of silver contained in the solution and rcdissolve it in distilled water. Second, if you had given your second query a thought, it would never have appeared in tho Mechanic; of course theobjects are upside down, and right side to the left. Third, are you sure the plate is exposed properly by pulling up the door of tho dark slide, and then taking the cap off the lens? or is the developer make according to formulae.— Tomkter.

£4647.]— PHOTOGRAPHIC—The effect of "Mendicus "having dissolved his nitrate of silver in so/t water would be that it would fog plates if iu a negative bath, and in a positive would render the paper mealy. Notwithstanding, if he treats the bath in the same way as I suggested a dirty bath should be in two or three numbers ago, it will be equal to one made with distilled water. Second, tho image that he sees on his screen is of course inverted on account of its being a " reflection" from the lens, and being inverted it i* of course reversed. Tho only remedy for it is to carry out the suggestion of a humourous photographer, i.e. turn your landscape upside down, and make your sitters staudou their heads. Third, the causes of no image appearing on the application of the developer are many : insonsltiveness, weak developer, under-exposure, too much acid and not enough patience. If " Mendicus " can get the back numbers from December last, ho will find all my formulas. He will not find it a waste of money,—on the contrary. But if he does not feel disposed to do so 1 will look back and let him know in what Nob. the formulae appeared. "Mendicus" cannot help getting an image with it. Hhe fail he had better look to his lens and camera to see that the " old gentleman " is not in them.—Mob.

[4648.J— COINS.—Tho first coin engraved la a aUver penny of William I. Inscription on the obverse," Ptlhtlm Rex," signifying William King; reverse, "Osmund on Sude," signifying it was struck by Osmund of Southward; worth about 5s. The second coin is a sixpence of Philip and Mary. Inscription, "Philip ct Maria, A.D.G.R. Ang. Fr. Neap. Pr. Hisp.," signifying Philip and Mary, by the Grace of God Queen of England, France, Naples, and Princess of Spain; reverse, shield of arms, with the inscription "Posviinus Deuin Adivtorum Nostrum." The numerals VI at the top of the shioldmean the value (sixpence); worth about 8s.—W.

J. EtiU-LKSTON.

[4648.]—TWO COINS.—No. 1, Penny of William I.; No. a, sixpence of Philip and Mary.—Bernardxn.

[4648.]—TWO COINS.—The first is a silver penny of William I. or II. Obvorso: full-face bust of the Conqueror, holding a sceptre iu hid right hand. Legend, PILLELM REX. (William, King). Roverso : a cross, with the letters P.A. X. S. in the angles: Legend, OSMVND ON SUDE (Osmund at Southwark). The name of the inoueyor and place of mintage. Common value, 3s. to 5s. The second coin is a sixpence of tho second issue of Philip and Mary, coined in 1554. It is rather scarco; value about 10s. For full accounts of theso two coins see my "Guide to English Coins." Part II., pp. 15 and 67.— Henry W. Hknfrey, M.N.S., &c, i&u

[4650.]—FRENCH LANGUAGE.—The best work I know is Havet's" Complete Class Book," Part* f.aud II., published by Simpkin & Co. Cassell's" Lessons in French, Parts I. and II., are very good, and will well repay careful study. Much more, however, depends upon continuous perseverance than upon the text-book. ** Don't try to learn French in si\ mouths."—A. Pocklinovton.

[4650.]—FRENCH LANGUAGE.—I have learnt very successfully from the two following:—" Tho Beginner's Own French Book." 'Js.; key to the same, *J».; by Delille. Should "Patty" wish to acquire a superior knowledge of the language he cannot do better than obtain the following in rotation :—" B«*y French Poetry for Beginners,"2s.; "French Grammar," 6s. 6d.; key to same 2s.; ** Modules de Poesie," 6s.; "Repertoire des Prosateurs Francais," 6s.fid.; "Manuel Etymologique," 2s. 6d. ; tho whole comprising Delille's series, which is pronounced by the leading professors as the best.— Piao:

[4651.1 —POWER OF WATER-WHEEL.—The rule for this is as follows:—Raise the radius of the wheel to the third power, and extract the squire root of this power: multiply this root by the area of the transverse section of the stream which supplies the buckets; divide the product by 6-5, and the quotient will bo tho mechanical effect iu horse powers :—

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