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of onr countrymen. You are becoming, if indeed yon Are not, as Mr. Batty (of Manchester) says, already, "Iui institution." I*have been casting my eyes about to see what other scientific journal yon are likely, to jibnorb, but as I do not know which oro weak or which a.ro strong, I will indulge in no speculation on the subject, and conclude by cordially congratulating you on your deserved success.

A Benefited Subscriber.

THE LINK MOTION. [104] Sir,—I find in your paper of July Istja letter from Mr. Harrison, in which he questions the truth of Mr. Baskerville's theory as regards the link motion. Now I advise Mr. H. before he so emphatically coutra«ticts Mr. B., to carefully examine Mr. B.'s diagram of the link, in your paper of June 17th. The link is there represented in "middle gear," and it is evident that the excentric rods must lose length in the direction of the motion line when they change from position A to position B, the loss being due to their angularity when in position B. Those letters refer to Fig 1.

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to the loloift, enabling him, n* they do, to produce those dashing and sparkling effects Bo charming to the ear. I know " personally" that the Boehm tlute has them to a great extent—in many passages they are indispensable to its system; but the Equisouant has them to a still greater extent, and the tone is much clearer and purer. I have spoken the truth, but I do not expect that any manufacturer or professor will acquiesce in what I have said if it be against his interests.

Tho late Mr. John Clinton was a great master, his magnificent transcription of Meyerbeer's exquisite cavatina, " Robert, toi que j'aime," and own graceful and brilliant "Grande valse—Reve d'uu Bal," are enough to establish his fame, to say nothing of a host of original works of which his reviewers have said sufficient. Ho lived but to sec tho only prize medal awarded to his flute " for improvements on the system of Herr Boehm," his early colleague.

Sable.

[graphic]

Throw of excentric 5J"

Advance of excentric .. .. .. • * 1'

Length of rod .. .. 5' 1"

Length of link .. .. .. .. .. 1* 4"

Lap of valve .. .. .. .. .. |"

Lead of valve \"

I send for Mr. H.'b instruction a diagram (Fig. 2} of a link motion. If he lays it out in two opposite positions in *' mid gear," he will find that the valve, or in other words the middle of the link, will move exactly 2i inches. James F. Ryan.

P.S.—A great many of your readers ore anxiously looking for a few good letters on iron girders and bridge work in general. If one of your clever correspondents would give us a few good rules on strains and the proportions of girders, he would confer a favour.

CLINTON'S PRIZE MEDAL EQUISONANT FLUTE.

[105] Sir,—Pray suffer me to thank "Jnstitia," page o7fi, very cordially for his generous and manly letter, which is a credit to both his head and heart; it is a refreshing contrast to that of "Orion." I expected Mr. Leftwich, or some more able champion than myself, would s.*on enter the lists in vtritatia ft jtutitiec cautam. ''Orion" did not think much of the fine flute of this distinguished composer and performer. A little sober reflection would have saved him from writing that letter in which he did himself a greater injustice than ho inflicted on Mr. Clinton's memory. "Justitia" has left me little to add in favour of the Equisonaut. Personally I know thit of it. Its tone is beautiful if it be fairly elicited; its notes are equal in strength, tune, and firmness, and it» great recommendation to flautists of the Nicholson school is, that its scale of fingering is natural, differing so little from the eight-keyed flute that it can be adopted with ease by ordinary players. These are advantages not to be overlooked. I need not, I am sure, remind " Orion," whom I strongly suspect to be in " the profession," of the great value of " harmonics"

POWERS OF BLOCKS AND STRENGTH OF ROPES.

[106] Sib,—I enclose a few diagrams of blocks and tackles which might be of service to many of our readers requiring such mechanical appliances. This subject has alreadv been alluded to in our Mechanic, p. 67, Oct. 8, 1869, but is there so imperfectly treated that I venture to bring it before you again in fuller detail and form. Fig. 1 is the singlo pulley, which only changes direction. Fig. 2 is an arrangement which gives power equal to 2 to 1. Fig. 8, the same, but is more convenient for being portable, and gives the first impression that the increase of folds gives the same proportionate increase of power. Fig. 4 having two sheaves in each block gives power equal to 4 to 1. Fig. 5 gives a power of 5 to 1, Fig. 6 a power of 6 to 1, and Fig. 7, a power of 8 to 1; thus showing that the increase of folds is the increase of power, and that the weight suspended in lower block is equally divided over all the suspending folds alike; and the weight required on the fold to suspend a given weight in the blocks is in proportion to the number of folds suspending lower block. Fig. 8 is Weston's patent blocks. The lifting power is given by the difference in diameter of top block sheaves, and the peculiar cross on the chain; motion given to which either adds to, or takes from .he length suspending weight.

And further to illustrate the principle of gaining power by blocks, Fig. 9 is a modification of Fig. 6, showing that by suspending 6 cwt. a strain of 1 cwt. will be the result on any part of tho line. The figures in the illustration correspond to tho balance of power attained.

To the above it is necessary to subjoin a table of the diameters, circumferences, working strains, and breaking strain of hemp rope for the above purpose. The rule to be observed is the working strain in cwts. on the old, multiplied by the number of folds suspending under block will give the number of cwts. which said block is safe to lift:—

Dia. Cir. W. Strain B. Strain.

Jin. = ilHin. 4*5 cwts, 1*5 tons

z „ = ai,, 6 „ 2 „

1 „ - 8| „ 8-1 „• 2-7 „

14 „ - H .. 10-2 „ 3-4 „

H„ =4 „ 12-9 „ 4-4 „

1|.. = 4J „ 18 „ 5 „

1J ii *= H n 22 „ 63 „

One third of this sum in tons is breaking strain. Say a pair of blocks two and three sheaves with 1J in. rope, what is the working power and breakUg strain on blocks and fold? On table working strain is 10*2 x 5 = 51 cwts. working strain on blocks, and divided by 8 is 17 tons, breaking strain on blocks, and this divided by 5, the number of folds, gives 84 tons as breaking strain on fold. J- Hovell.

ACCUMULATING AND UTILIZING POWER. [107J Sir,—Will you allow me ^pace to make a few remarks upon your correspondent's query upon the

above as contained in your journal of the 1st inst. which I have just seen? "River Plater" asks if it is possible to accumulate sufficient power, whether by moans of horse or wind, as to be available at some future time. I shall not attempt to answer such, but will state what I heard in the River Plate (Buenos Ayres) in 1857. When locomotives were first introduced on the Western Railway, a native asked me what was the power of each locomotive. I told him so much. His reply was, " How so: I do not see any horses in the machine? where do yon put them?" and when the steam was issuing from the funnel, a cry was set up it was "white magic." There are snch objections as your correspondent points out, attending the cost of coal^ but to wait until the plantations are large enough to supply the fnel consumption is absurd, because colonization increases in a much greater ratio than the fuel (trees) can, being only planted lately.

To invent a machine that shall have a spring (so to speak) capable of being wound up to supply power for even the next day, for such a thing as a Fowler plough, would be attended with considerable difficulties. Now to accumulate the power of horse or wind to such an extent is impossible. Water power is considered the most available from day to day. Under ordinary circumstances we can depend upon it, yet in the River Plate provinces snch is not at all to be depended upon. I have crossed the "Soniberainbom" when my horse could skip across, and in a few months I have ridden fifteen miles throngh water before coming to the same river. Having spent several years in this country I am enabled to speak from experience.

I should try and introduce the "Aydon Liquid Fuel" as being cheaper, a more ready generator of steam, and far better for transportation.

There are other materials for fuel in the sister empire far better, and less expensive, tlmn coal.

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[108] Sir,—Perhaps some of your correspondents will give me their opinion respecting fast or moderate grinding—say, whether they prefer six to eight bushels per hour, or from three and a half to four bushels per hour. It is my opinion in fast grinding yon lose your colour, also your lougth. But there may be some one that can tell how to get both. I have heard a great deal about Bovill's cold blast and exhaust; the cold blast lam hard of believing in. But, as I say, perhaps some of your more intelligent correspondents may give me their opinion respecting it. Also, what length should you have a silk for (say) six pairs of stones grinding (say) four bushels per hour.

A Subscriber.

THE SUN'S PARALLAX.

[109] Sir,—Referring to " Hugo's " letter upon the sun's parallax, on page 402 of the English Mechanic of July 15, 1870, before answering that letter, will you be kind enough to allow me to ask "Hugo" to test or verify his figure by actual calculation, as he says "he is confident the parallax thus formed will be that which is generally accepted to be true?" The mean parallax of the sun is given by some at 8'"91, and by others at 8"*65, Ac., Ac. "Hugo," I submit, is bound in honour to give by actual calculation what he considers the "t nir" mean parallax of the sun, because he has said that whiah has been given by " Veritas " is not "true;" otherwise, how does be know?

Veritas.

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circle. The inner lino of the rail ¡s described parallel to the onter one; this will always givo the open space required for the hand. Cranio.

THE "PIÎŒNIX" VELOCIPEDE.

[111] Sib,—Having been greatly interested in seeing the numerous and varied description!! of velocipedes which have been illustrated and described Lu the pages of your interesting and valuable paper, I wish to offer to your readers a brief outline of a three-wheeler, the capabilities and qualities of which I have fully tested daring the last twelve months. I have named it tho " Phoenix," partly on account of several important parts having been used in a somewhat similar machine made by my father over twenty years ago. It is constructed to carry two persons; the front wheel (3ft. diameter) is fitted with a steel axle and cranks; and is mounted in a fork with a steering handle on the top, exactly similar to the front part of au ordinary bicycle. The two hind wheels, each 8ft. fïiu. diameter, ¿re firmlv fixed on the ends of separate axles; the inner ends of these axles working in one bnsh fittod in the frame, gives the appearance of being only one axle. Ou about tho middle of each of these axles is fitted a steel ratchet wheel, and loosoly over these are cases having each three pawls; these cases have grooves on the outside in which are secured the ends of strong catgut cords.in which passing over the cases go down to lovers or treadles provided with india-rubber footsteps; the levers are also connected together by a catgut cord, which passing over a roller, so the descending lever lifts the other. The advantages gained by this arrangement of three wheels are—great facility of steering, especially taming sharp curves, as each wheel being on a separate axle, they work independently of each other; the ratchet wheel and lever arrangement for driving tho hind wheels gives a powerful and convenient mode of working for the second rider; and there being no dead points (as with cranks), iu whatever position the levers are placed at stopping, they are right for starting. In going down hill he can rest his feet on the steps, as the wheels can go independently of them. It will be seen from the description of the front part that the rider thereon works and steers just the same as on the ordinary bicycle. For two riders I consider it to be the best machine I have yet seen or read of, and shall bo glad to learn tho opinion of my fellow readers of tho English Mechanic. W. D. It.

the back and filling iu with lead iu order to counterbalance au overplus of weight in a bur or burs in the face at the opposite side. Now, as the lead is 5in. above, and the heavy bur or hnrs (intended to be counterbalanced) Sin. below the contre of the bar or bale, the consequence must be that as soon as the stone gets into а swing, centrifugal force must bring the lead down and the heavy bur np, just as the balls of a governor have a tendency to rise to the level of fulcrum on which thev aie hung; now, if my dusty brothers who are troubled with stones being out of standing or running balance, will only dig out a hole between the hoops as near as possible to the nipple of the slow spindles, and pour in the necessary weight of lead, I do not doubt they will find tho stone cured of its tendency to roam. Í have known millers who prefor the plan" to balance boxes, bocanse it is not possible to get out of order.

Iu reading Jas. BaskervíUe's criticism's on Llall's water heater, which I thought an excellent plau for feeding a boiler with one pump, I tmst I shall not bo intending if I describe a water heater which I put up in 1863, and have still at work—the engine, a 10-horso beam. I pump the cold water directly into tho exhaust pipe, a few feet from the cylinder, 'the exhaust pipe going horizontally to the heater or depositing reservoir, as it may be called, as the water is really heated by the cxhanst steam, driving it into the heater in the shape of a fine epray, thereby heating it nearly, or quite, to 212 degrees, as can be proved by drawing ont of the suction pipe of tho hot water pump through a tap, when a pail full of water so heated will register 207 degrees ¡ by this means the water deposits its silex m the heater instead of carrying it into the boiler. My heater is 7ft. long by Hin. diameter, lying in a line with the exhaust pipe, and I can hear the spray blown to the end at every stroke of the engine. I have an overtlow pipe at the middle, also one rising to the open air. I condenso many gallons of water bv this means, and save fuel. I have seen somewhere that 9 degrees of heat in boiler-feed is equivalent to 1 per cent, of fuel [saved, so conclude 'that I save 14 per cent., besides the advantage of having soft water for the boiler. I am obliged to clean the exhaust pipe once a year from silex, as I once had it form so thick as not to be able to drive one pair of stones with í.ílbs. of steam. I also find it necessary' to have the heater a little above the hot water pump, or it will not draw. One Eye.

BICYCLE RIDING.

[112] Sib,—Your correspondent "N. 0. Lamborne" asks for answers to several questions which, as a practical bicycle rider having had fifteen months' experience, I think can ho easily answered. It does not require any great amount of practice to enable any lad to ride on a smooth road. A week, with an hoar each day, would be amply sufficient. Of coarse some care must be exercised, but nothing extraordinary. If the bicycle is bad the best of riders could not prevent it wobbling, but nnless the road is an extraordinarily bad one this would not happen with a good machine. There is no danger to a practised rider when|passing a waggon in а narrow road, for the bicycle has an advantage over any other vehicle in that it can run in so little space, besides being able to ran into the grass if that skirts the road, or into tho gutter if in a town road. I never saw any danger of falling in turning a sharp corner, but cannot say if there would be if going at great speed, which is a dangerous proceeding with any vehicle. Power over the machine is lessened, but never lost with a good rider, and if the front wheel rubs the thigh it is an ovidence the rider needs practice. It is possible, but not likely to happen to a good rider, to pnt his1 eg throngh the front wheel any more than the hind one.

The comparison between the sitting ou a low chair placing tho feet 18in. forward, and then trying to riso may perhaps apply to a case where the seat of the bicyclo is far back on the spring, but in my machine yon are so well forward that one may almost say thoy sit over the front wheel, wliich, by the bye, I believe is rather a rarity, although a great benefit to the rider.

I shall believe iu rnntures when I have some personal knowledge of their having resulted from riding.

As regards personal injury in jumping, or rather bucking, on to the bicycle there is no necessity to do so with the majority of machines.

Upon coming to a very steep hill yon have only to ask yourself which wonl'd be the easiest, to work the machine np to it, or get off and walk it up, in which latter case thero is no need to dirty oneself. I think I have answered most of the questions, if not all, fairly, but I must say that the space von have granted this letter is wasted, for had " N. O. Lamborne" asked any bicyclist the same questions I have no doubt he would have obtained the same answers. I quite agree with those correspondents who speak of the nonsense so often sent yon respecting the now machine. I feel snre that.mau v who write never sat on one for five consecutive minntes, and believe that many who abuse it gave up just when they were getting into the use of it, for I have never met with any on о who had ridden a machine for any length of time but who would say with me, " Bless the man who invented them," and rejoieo over the many happy honrs they have experienced since becoming practised riders. E. S.

MILLSTONE BALANCING. FEEDING BOILERS.

[113] Sir,—Kindly allow me space in your valuable paper for a little say on mill-stone balancing.

I often wonder that no one has noticed the fact that mill-stones are usually balanced by digging a hole in

PROFESSOR PRITCHARD'S REVIEW OF
'• OTHER WORLDS."

[1141 Sis.—As an old reader, may I bo allowed to entera word of protest against that practice of indulging in personalities, which every now and then crops out in your "Correspondence" column? Although it may be highly entertaining and gratifying to tho tasto of some, I think I may say with truth' that it is quito otherwise to the majority of your subscribers.

I think Mr. Proctor has shown very bad taste in criticising Professor Pritchard's review of "Other World ¡. In the first place, for answering the critique at all, since if it be an unfair one the merits of the book itself will themselves answer the criticism, and if the roview did not do it an injustice, why, the loss said about it the better. Then, iu the second plaoe, I do not think it was exactly the right sort of thing for Mr. Proctor to insert letters upon a review (whioh appeared in another publication) in the English Mechanic, which perhaps Professor Pritchard does not ordinarily see. It seems very much like trying to steal a march upou Professor Pritchard. I am afraid that Mr. Proctor is very thinskinned. Charles Brandon.

THE BICYCLE. [115] Sib,—As a votary of the bicyclo I ask the liberty of answering N. Ü. Lamborne s questions on this subjoct (page S76l. The number of his questions mn^t be an excuso for brevity iu my answers.

With an hours daily practice ono will learn to rido over a smooth road without falling in a week. The twisting motion on a bad road would no doubt arise from the inexperience or carelessness of the rider or his desire to avoid all stones 6o as to save his machine (and India rubber tyros) from getting over them. If the curvilinear motion was iu reality to keep the rider from falling he must not have been up to much and ought therefore to be free from all judgment. There is the same danger that the fusee will touch one's nose, iu lighting a cigar as that a bicycle rider will run into a carriage; in all such cases take cere, trust in Providence. There is no fear, to ono up to it little possibility, of falling in turning. By the ex-position of the crank in turning mechanical power may be lost, but not such as to cause any inconvenience to an adopt. Tho "power over the machine " is not lost by any ox-position of tho crank. In common turning the wheel does not rub against the thigh. It is only in very short turning that it does so. Bieylos are now provided with log-guards which do away with all thigh-rubbing. Thero is no moro chanco or danger of the foot going through the spokes while riding than of one foot catching behind the other when running or walking. No resemblance whatever. The thrust in a bicycle is between a forward and a downward pressure. The force is similar to that required to push the chair backward with the foot restingon a low firm stool. The samo danger above exemplified. A railway guard in stepping from a moving train runs a similar danger He might slip. Very likely. The papers delight in those things. Railway accidents. &c. Place the hand on tho spring somewhere behind the saddle and walk alongside Or, if the hill is very steep, rest tho elbow of one arm upon the saddle and guido with the other hand. The saddle is as good »s any walking stick. '• Lugging "isa word that eannot tie used to the bicycle nnless it is made on the waggon principle.

Bicyele riding being comparatively spooking something new, is looked upon bv John Bull in his usual philosophic style. That wary gentleman accopts nothing in a hurry. 8haking his head, his story is "It may be all right, but I don't know yet." Ho very well exemplifies "Novalis's,' statement that to bcoomo properly convinced of any fact you must first have disbelieved it and

disputed against it. That is his plin of welcoming ¡ill novelties. The French are diTerent. They are at ont» enthusiastic, and the bicycle is tho machine for them, iIs thrir machine. But though John Boll is too solid «oí conservativo to trust himself at on<-o on two wheelyet ho is turning round, so much so that I'm convince ho will in a tew years adopt the bicycle as a useful an' pleasant mode of convoyance.

When I got a bicyclo and began to practice on it mis' people hereabouts pronounced it as fully. •• \ creatd-i' of hard work," and that it " would have itodav " wastv usual cry ; but twelve months have altered their opinion. for upwards of two dozeu fellows of our small town have sineo become riders.

In further answering " N. S. L." I may state that andoubtedly the bicycle is a better machine in every wai than the three or four wheeler. I sneak from m'y own knowledge. Let "N. S. L." and all his proselytee'lear:, thoroughly the use of the biorcle—- which, it is cvidm' ht knows as yet little about—and the-v will at once dil card tho multicycles. It requires less exertion to drive The force applied is direct and in the proper and misnatural and easy direction. It is safer and quicker in turning—with many other indisputable etceteras

I have never yet gono fifty miles at a stretch, but iu this respect I'm behind many of my brother riders. Bui I can nde over most hills, although overeóme the sweat ing (not so much the labour) is great.

There is still one " moot point" to bo settled which

S. James" (page 874) has already laid before your readers. We want an impartial anil well grounded medical opinion which must be given in full length with causes, effects, and reasons, whvs and wherefore« all annexed. For my part I can say that I have ridden continuously for hoars together and never felt any evil or rapturous effects. Hcsbaw

THE FLUTE.

[11(5] Sir,—In this week's ENOLisn-jECTiANlcIscetha' a correspondent,"T. S.O.," advises -'Stiff Fingers"tophiv in certain keys and to produce some of the others by thé tuning slide. He says "the music boing in D flat he should by means of his slide tune to the D flat of the piano." It is quite evident that "T. S. O." has had but little experience, or he could not have advised such а course. The smaller a flute is, the nearer the holes «nd keys must be together. In a piccolo, for instance the distance between the holes is only half of what it is in the concert Ante. If a flute is lengthened by the toning slide, it mnst play out of tune—particularly in the upper octave. The tuning slide is only intended to miter the pitch very slightly, say j, or at the wort,} of a tone.

J. R. Revdell.

SWIMMING, A SUMMER PASTIME. П171 Sin,—I wish tolthank " T. S. H." for his verification of my determination of spheri.-al route M cirenmnavigation, and in reply to his call for a few notes on swimmin«, I beg to offer a few from my own experience I hed a wish to learn this art from early lite, but my avocations led me generally inland, and to places where practice was impossible, till I had passed the middle term of human lifo. At last I camo to within a mile ot convenient water, and although mv past limited experience led me to suspect that ' I was specifi-laliy heavier than water, as my efforts to swim were always brought to a termination by tho sinkinc of ttae whole body, head included, below the water, still I reHolved to bring the matter to a test of a whole season's dailypractice before considering my suspicion confirmed. For some timo this was like to be the case, bnt at length, in ono of my daily trials. I found iny head, quite unexpectedly, above water. I was at a lo9s then to assign w satisfactory reason for this result, for I had often struck with both hands and feet -precisely, so I thought, in the same way, with a different result.' Be this as it may. I never sank after this, and I found mvself on each successive daily trial able to accomplish a'few more strokes till at length I swam on one occasion, fifty minutes without feeling cold or fatiime, and without touching the bottom. I need hardly say that' the practice' still continues to lie a source of refreshing em'ovment to me: bnt although I can swim quite cunfortnhlv for a lonn time, when allowed to do so leisurely, still I find myself a «loir swimmer whatever efforts I choose to moke. I am at a loss to explain to myself tho reason why; but the reason of my early failures, the sinking above referred to, I now conceive to be that I unconsciously kej't my head in line, or nearly si, with mv body, wherei' there ought to be en an<rlo fomewhere about 135 degree between the axis lines of tho body and tho head. ТЫ' angle is not quite so easy a matter to ol tain a« could Inwished, and here lies the difficulty, in my opinion. We experience in learning to swim, a diñic'ütv peculür to man as distinguished, by form, from many animals that swim Willi enso on tho first trial; and hence also tindcsirableness of Ьагшпг to swim on tho side and back, in which position the anulo at the back'of the neexbeeonu s 180 degrees, and the position is consequently one of complete rest. Not only is it a position of rest,'but the body floats without any tendency whatever to sink, with no muscular effort in either arms or legs; a ven- slight effort in the muscles of the loins being nil that is necessary, so far as I can judge, to preserve the linear position of the body from head to feet. In this position there is about liu„ vertical section, of tho face that positively will not «¡nl The effort to throw the head under water rosults iu a deeper immersion of the forehead with a greater cone sponding elevation of the month, and thus the position is a most happy one to rest in for any required time, or even to wash the feet and body generally with both hands, for it appears to me generally certain that tbfloating of the bodv does not depend, in any sensible degree, он the position of the arms so long as thev ну kept under water. I conclude generally that to 'swinn swiftly and gracefully is a difficult matter for most men . but that every man's body iMl float, and that almost anv aclion with feet and hands, all four at once, or any pair at once, will produce progression, moro or less swifllv and gracefully according to the symmetrical action of the whole system. M. L.

M. DR Lebsep-s is reaping the reward of his Ingenalti Ho has been feted everywhere, and is shortly to be presented with the freedom of the City of London.

EXTRACTS FEOM OOEEESPONDENOE.

GAS- "J. G." says:—"I do not however agree with yuur correspondent's remark tliut, * (Jarburettiug Gas' i* at present nut a practical process. The Commissioners of Sewers for the City were so alive to the iieucflt derived by such process that they ordered lfcUX) to be fitted to the street lamps according to the principle «>f Mr. IF. Ridd finding a saving of about 30 per cent, by their adoption. Mr. George Glover, the gas meter manufacturer, also proved the benefits to be derived by tli*ir adoption, the illuminating power caused by their introduction was about 43 per cent. Tue Midland Railway Company have had them fitted to their pendant lumps at the new station at St. Pancras, beside which numerous private firms have adopted this improved system, thus proving that your correspondent's remarks are not tenable."

CURIOUS QUESTION'S.—"J- B." says:—"In reply ~.o K. Gould's first question (page G78), there will be no difference because the ball, atmosphere, and all else on tiie earth's surface partake of the earth's motion, " orbital" and^rotatory, which consequently in no wise affect the relative motions or positions of such objects and the earth inter w. Secondly, if the word * spaeo ' is intended to mean 'as measured on the earth's surface,' there will be no difference, but if it be taken in any other sense the difference will be so much.plus or minus, as may be caused by the earth's motion during the flight of the bull."

TRADE AND COMMERCE.—"Sigma " concludes a

loag and elaborate letter ou this subject thus:—''Last and moHt crushing of all, we have had five-aud-tweuty yenrw' experience of the working of free trade and ought now to be in a position to judge of its effects.' True— what is the total population now and twenty-five yoars ago, what the total income or eveu the average income of the nation? If free trade is a luring gatm-, gradually impoverishing us, how were our railways made; where did the shipping come from which covers every sea; whence came the capital sunk in establishing colonies for our extra numbers:' In fact has the supposed loss diminished our capital, and how? In London alone each year a new city is built. Walk through its bounds and count how many miles of houses there are requiring large incomes to support. Whence those incomes, whence our increasing national revenue? Take a fair view of tho present and twenty-five years ago. Look on this picture and on that, and verily if these results be the inevitable consequence of annual loss and impoverishment, thou, but only then, is free trade a failure."

POWER LOOMS.—"J. W." says :—" I hope shortly to he able to furnish you with drawings and description of some valuable and beautiful improvements in power looms which I am now patenting. I have had two of our principal English machine makers here to see them within a few days, including Platts, of Oldham, who appear to attach importance to the Invention—and I expect to be in Manchester next week with the viow of exhibiting the machines and of arrangiug some licenses."

REPLIES TO QUEEIES.

[2637.]— ELECTRIC LOCOMOTIVE.—There is not I believe as yet discovered any practical mode of obtaining motion from electricity which is capable of being utilized. The reason being that the law of "magnetism" which seems to l> _■ the only form in which it can be employed is that tha force varies inversely as the square of Ike distance from the magnet, which obviously reduces its available power to within exceedingly narrow limits and consequently almost forbids its use as a mechanical power.—J. B.

[3642.]—PISHING RODS.—" A Young Tyke" roqnires hints how to make a fishing rod about five yards long. The very best advice I can give is "don't." Such work is done by skilled workmen so cheaply that it don't '* pay " to do it oneself. I have been guilty of that folly in my youthful (? verdant) days ; but long ago I became a good boy and "didn't do it no more." If " A Young Tyko" had any idea what it would cost him for the mandrels, or triblots, on which tho ferules must be hammer hardened (or their mouths will become anything but musical trumpet*), the tools required to bore out the joints, the difficulty of making one joint go straight into the other (unless you do as I did—viz., bore thorn in a suitable wooden pillow-block, which I had to make for the purpose in the Lithe), and the time it takes an amateur, who is seldom so much of an expert at such operations as even my humble self, to do this work he would thankfully receive my good advice, "don't"—and not set to work on operations as little worthy his time as grinding specula, or lenses for 0. G.'s and eyepieces, would bo worthy to occupy the time of an observer like our " F.R.A.S.", which I suspect might be more nobly and worthily employed in reviewing "The Fuel of the Sun," orviowing that luminAry himself. Some advice I tender. Don't make a rod, or have one made— unless it is to be only one of several rods—so short as five yards. Make it seven yards while you are about it, and have two extra short extra butts made to it, one to receive its largest joint, and the other the next joint. Yon will have, supposing the rod has five joints (never have more), seven yards; six yards, and four and a half yards, quite sufficient variety for all purposes. The best kind of wood is, in my opinion, well-selected South Carolina bamboo cane. A north cane top, with a point of split jungle about a foot long I prefer to any other, but a good hard piece of south, although from its numerous channels ugly, answers very well, and north is difficult to procure rsutficiently long and taper to make a first rate top a yard long.—The Harmonious Blacksmith.

[3613.]—IRON PRISM.—Original sise of prism Is 3ft. long by Din. wide, and deep plate required will be 54in. square by lln. thick.—J. B.

[8648.]—IRON PRISM.—If I understand the question aright a square prism of iron containing 2,916 cubic inches ia to be flattened into a square plate of uniform thickness, containing the same number of superficial

inches, required the size of iron plate. Therefore «y2iJ16 = 54 inches =side of square plate 1 inch in thickness.— Harby G. Newton.

[2643.]— IRON PRISM.—How can a superficies which consists of square inches be equal to solidity, which is a cubic measurement. Also what has the shape of the prisin to do with the form of the plate that has to be mado out of it, which latter we are told is to be square and of uniform thickness ?—J. K. P.

[2652.]—SULPHATE OF ZINC—Extract. "Sulphate of zinc, or white vitrol, ZnO.SO* + 7110 is prepared by dissolving the metal in dilute sulphuric acid, or more economically by roasting the native sulphuret or blende, which by absortuug oxygen becomes to a great extent converted into the sulphate of oxide ; the mineral is then thrown into hot water and tho salt is obtained by evaporating the clear solution. This salt closely resembles sulphate of magnesia in appearance, it has an astringent metallic taste, and is sometimes used as an emetic; the crystals are more soluble in cold than in hot water. This salt forms double salts with the sulphates of potash and ammonia."—Hakkv G. Newtox.

[2668.]— SKETCHING FROM NATURE.—At Johnson & Son's, 16a, Basinghall-street. Acetate of cobalt, 2s. oz.; muriate. Is. Ud.—R. Sedu Field.

[2677.]— HYDROGEN GAS FOR BALLOON.—Manymore details are needful to enable a truly correct answer to be given to this query. The weight of the ballon, tho height of the barometer and the purity of the gas must be first ascertained. But assuming the gaa to be pure, its specific gravity is 0-555 as compared with one of atmospheric air, consequently 1,000ft. of gas will support in air 41*39911)., and if your correspondent will calculate on this basis the number of feet of j^a* which will lift himself and his balloon the weight of irhieh latt he must assume or ascertain, the cube rout of that quantity divided by 3*141 will give him the radius of the tpherical balloon which will contain it with sufficient accuracy for his purposes, which I venture to presume are not practical.—J. B.

[«JW.]—ENGINE CHIMNEY.—lam of opinion that a chimney 95 yards high having a flue 3ft. in diameter will do the work ret|«ired by " A Subscriber."—K.

[3716.]—RELACQUERING BRASS WORK.—Brass is dipped by passing it quickly in and out of the nitric acid. If tho action does not take place during the first second tin* leaving the articles in longer only turns them black. The process should be thus to dip articles bright: Scrub them after taking them out of tho soda water with sand and a brush, then briskly, pass them through the acid, and immediately wash them in a pail of clean water or hold them uuder a pump. If not quite clean after the first dip scrub the part again, and put through the process a second time, only remember that the oftenor they are dipped the more dead the colour will become. *A little urine to dip articles into before passing through the acid and after scrubbing has sometimes a very good effect; eventually dry out by stirring articles up in a bin of sawdust. The quicker these processes iro gone through the brighter and better the work will become.—Wm. Holmes.

[3716.]— RELACQUERING RRASSWORK.—In the first place, if tho brasswork is ivory dirty, and not come clean enough for the acid to act on, it should be left in tho acid for some time, then dipped in fresh acid; but before bein^ dipped in the fresh acid, he must take care that all tho dirt is removed before being dipped again. The reason of the articles turning black is because they are not properly clean before dipping, the old acid will make very good pickle.—W. Skabbook. [373G.]—CHROME BLACKS.—" For 101b. of wool or woollen cloth," boil ono hour in a solution of 4oz. chrome, 4oz. of bittartrate of potash (cream of tartar); then wash out of this solution, and boil in a solution of 101b. of logwood for ono hour.—R. R., Rochdale.

[3738,3766.] —BAROMETER TUBES.—Without knowing of what the film is composed it is difficult to say what will remove it. But a strong solution of soda, with or without heat, would be very likely to do so if well shaken, and some small shot inserted in the tubes at same time might by their friction oxpedite the process. Tho tubes may be filled by inserting the mercury by little and little into the siphon end and shaking it so as to allow the air to escape through it, or tho air in tho tubo may be rarefied by heat, and if the lower end be then plungedin mercury, the air as it contracts in cooling will draw it in and this process must bo iu either case repeated till the tube is quite full, when it should bo held upright so as to allow the excess of mercury to run off. For philosophical purposes greater care, and more adjustment and calculation, is needod than can be explained in few words.—J. B.

[3781.] —PHOTOGRAPHY.—Thero are various changing boxes made for the dry process, but they are all rather difficult to explain without several drawings. "P. M.'s" best plan would be tooaU at some maker's, and examine one. Tho vortical developing-bath is never used nowadays: it is a wasteful^plan. If "P. M." finds a difficulty in getting the developer to flow over the plate, let him add to each pint, from one to two grains of common gelatine dissolved in a little warm water. It will then flow readily, without Btreaks and markings, which are sometimes difficult to avoid without the gelatine,—R. S.

[3807.]—PAINTING STONES IN JEWELLERY.—If "T. G." will examine the setting of any coloured stone, he will find that the silver foil placed behind it is lacquered of the same colour a* the stone is intended to be. Some stones are capable of having an artificial colour imparted to them by heat.—A. S. C.

[3832.]—BURNISHING PLATE.—Tho tool he requires is an ordinary steel burnisher, which can be obtained at any tool rahop. He must rub the scratches well with it, and he will soon find them disappear.—W. Seabrook. [8842.]—STEEL WIRE.—I did not answer " J. R. T." (3842) for the worst of all possible reasons—i. e. because of mine incompetence to do so. I inav as well remind him, if he has not yet become tired of his fad of model church erection (by the way he had much better go to one ready built), that Bmall bells only cost a few pence each, and what he calls wire gongs have a very disagreeable tone.—The Harmonious Blacksmith.

[3844.]—ENTOMOLOGICAL QUERY.—Larva of Cotmia trapezina is of a dirty green colour, with its dorsal, subdorsal, and spiracular lines white and spotted with dark green. Let "E.N." boware of the larva of Scopelo*oma tatellitia also. It is dark black-brown, with three

white lines on the second segment, and a white spot on the second, third, fourth, fifth, and twelfth segments, below the spiracular line.—Automedon.

[3844.]— ENTOMOLOGICAL QUERY.—I send for "E.N." the description of C. Trapezina (larva), as given in " Stainton's Manual," vol. 1,page258, "Larva greenish with the dorsal, sub-dorsal, and spiracular hues white; tho spots black or dark green. On oak, birch, &c, especially fond of other caterpillars," appears in May and June, abundant everywhere.—A. 8. C.

[3349.]—STUFFED CANARY.—"Excelsior" can clean his canary by rubbing it with a piece of clean whito wadding. Afterwards ho may pound a small piece of chrome yellow and sprinkle upon it and then brush off off again with the wadding, tempering it to the shade with dry whiting.—Ignorant.

[3858.J— HOLE IN EARTHENWARE.—I think if H. Joseph drills a circle of holes, lin. diameter, with a small Archimedian drill, and knocks the centre out, he can file it down smooth with a medium file.—H. A. C.

[3858.]—HOLE IN EARTHENWARE JAR.—A hole may bo bored by a common blacksmith's drill used lightly, and it had better be not more than Hu.., after which the holo can bo enlarged to any size with a half round file; or a sharp point, with repeated blows of alight hammer, will quickly penetrate the jar, care being taken not to strike so hard as to cause a crack, and the point to be kept moving from place to place.—J. B.

[3859.]—FLORENTINE BRONZE.—In answer to H. Joseph, I beg to inform him that to bronze the articles he inquires about, he should boil them in strong soda water, scrub them with sand, and dip them in aqua fortis; then lay them in a weak solution of the same acid, about one part acid to eight of water, into which he must put some pieces of iron wire; he will find them turn a red colour. After leaving thein about two hour3, take them out, dry them, aud lacquer them with red lacquer.—W. Skabkook.

[3873.1—BOOKBINDERS' GLUE.—The beat method of making the above is to break the glue into small pieces; then put it into a glue-pot; cover it with cold water, and put it on the fire; stir it up frequently, and, when melted sufficient, use it hot. It must not be too thin or too thick. A little practice will soon put you right.—J. Plastans, 55, Dale End, Birmingham.

[8875.]—BLEACHING POWDER.—Bleaching powder ia made as follows :—It is a mixture of calcium hypochlorite, or chloride. It is produced by the action of chlorine gas upon moist slaked lime. The gas is passed in rooms, on the floor of which is laid the lime «in. thick, which absorbs the chlorine, and tho powder is formed. "When treated with a small quantity of a dilute acid, hypochlorous acid is liberated, and may be distilled over. Hereby an Aqueous solution is obtained as a colourless liquid, having a peculiar smell and bleaching properties. If a larger quantity of acid bo added, the hypochlorous acid itself is decomposed into hydrochloric acid and oxygen. Hence, in bleaching, the goods are first dipped into a solution of bleaching powder, and then passed through a dilute acid, whereby hypochlorous acid is formed and decomposed, liberating chlorino in the fibro of the cloth. Tho bleaching effect is therefore only visible after the goods have been * soured,' or dipped in acid." (See Roseoo's "Chomistry.")— H. A. C.

[8877.]—RETINNING HOLLOW WARE.—Well clean the inside, and lay them in a bath of muriatic acid; then put some muriatic acid and sal ammoniac iu and a piece of tin; hold them over a coke fire till the tin melts; then with a piece of tow wipe the tin round the inside; leave them till cold, and rince them in water.— W Seabrook.

[3941.]—MARKING.—The best way to apply printorfi' ink is as follows:—Get a little cotton wool; tie it up in a little soft leather; put a little iuk on it, aud dab it on a flat surface, either iron or stone, till it is spread even. Then dab it on tho typo till it is inked all over; then press the type on the articlo you want to mark. Writing marking ink is far more durable.—J. Plastans.

[3985.]—FLEXIBLE PIPE.—India rubber canvas hose pipes (vulcanized) will stand hot water, and so will leather, but if only a small size is required vulcanized India rubber will be found cheapest.—H. U.

[3989.]— SCREW ENGINE FOR CANOE.—What doos "A Young Subscriber*' mean by wantiug an engine for a " canoe." Either his boat is'not a canoe or he wants to alter it into a steam "launch." What is really tho shape of ii, and what is tho width? He says in his query about 2Jft.—H. U.

[3993.1— PASSAGE TO NATAL.—"A Cornishmau" wiil find that the " best" way toget to Natal is to take a first-class berth on board the mail steamer; tho " cheapest'' is to irorJfc a passage out. Seriously, there is a regular line of traders to Natalleaving London, and ho might find a captain willing to tako him for his labour and a money consideration.—H.U.

[8990.*]— BOOKBINDING.—Brass type would be bost for " An Amateur;" it requires great care, and a deal of practice, to use single letters. Leather is all prices, from 2s. 6d. to 12s. per skin; calf aud morocco are very dear; bookbinders' cloth, from 8d. or 9d. per yard.—J. Plastans.

[3999.J— CYLINDER.—If "Ixion"gave the size and weightof his steam carriage ho might expect somo one t«> give him the dimensions of cylinders for it. How it ia possible to sav what size they ought to be without knowing the work required of them I do not comprehend. —H. U.

[4007.]—CURING HERRINGS.—I do not imagine Mr. Baskerville ia (likely to find a book containing any authentic directions for the process he requires, so I will tell him what I know about the matter. The method of enring herrings varies with the place of curing, and the state of the herrings. At Yarmouth, off which port the shoal is in prime condition, two methods are pursued, and the fish are known by the names "bloaters" and "high-dried." The bulk of bloaters for tho London market are simply taken from the boats and laid in barrels or troughs, with salt between oach layer. After remaining iu pickle 24 hours, they aro hung up to dry in the amoking-houses, but they are not subjected to any large amount of smoke. They are ready for packing in three or four davs, and are httle more than fresh herrings dried, with just sufficient salt to keep them a week or so. The proper bloaters, although they are not kept in salt much longer, are really smoked over tires made of uak saw-dust (at least that is what should be used), They will keep some considerable time. The "high-dried," As their name implies, arc kept in pickle till they are thoroughly Impregnated with salt, and are then taken to thci smoking-room* and allowed to hang there till they are, so to speak, "tanned," in which con lition tlicy will last a voyage round the world, and then be good. The Scotch herrings, and those canght in St. George's Channel, are made into "kippers" in large quantities, or else are treated to ruther too much salt. The reason of this is, that the flab having spawned, the roe would only act as a predisposing cause of putrefaction, although, strictly speaking, this does not apply to Scotch herrings, which arc turned into "kippers" for convenience in packing, especially as they are then worth as much commercially as the others, and farmers buy up the "offal" for manure.—Saul Rymea.

[4012.] —WORM-EATEN ORGAN BARRELS.— "Pupil " will find a solution of corrosive sublimate the best cure for worm-eaten wood. It is a violent poison, and great care should be exercised in using it. The ordinary price is 6d. the oz.—Saul Hymea.

[4064.]—MICROSCOPIC INVESTIGATION WITH POLARIZED LIGHT.—Micro-chemical testing differ from ordinary chemical analysis only in the use of the microscope to observe the effect of reagents, and I do nut know that I can give " John Barleycorn " any hints which will be of any use to him, as he doubtless is already au fait at so much of chemical analysis as applies to testing for acetic acid. Cry$taU of acetic acid, like most, if not all crystals, will polarize, but only in tho form of crystals. If "John Barleycorn" can.persuade the acetic acid in his liquor to crystallize on his stage plate he may succeed in polarizing, but I suspect that it is usually found in so small a proportion* that this will not be possible. For polariscopy objects must be mounted in balsam or in fluid (glycerine answers well for many objects}, and the two glasses (that of the slide and cover), should be thin. Tho polarizer must be fixed in its [place beneath the stage, the analyzer also being in its position, light should be thrown fairly into the polarizer by the plane mirror if possible, though the use of the plane mirror is not necessary, and the prism rotated to see if all light bo cut off twice in each revolution. This is polariscopy in its simple form. Most of tho objects commonly viewed by polarized light are seen by this arrangement in a ghostly kind of light on a dark ground, and if colour be wished the use of a thin film of selenite is needful. Those are commonly used of such thickness as will give red and green, blue and orange, yellow and purple, the latter being by far the best. To secure the best effects it is necessary to " set" the analyzer relatively to the axis of the selenite used— this can be got by experiment, by slightly rotating the analyzer as well as the polarizer, till the best effect be obtained. Some objects require a special "setting "of the prisms and it is usually advantageous to try all possible positions of both prisms, as much may in this way be learned, which otherwise would have remained unlearned. Of mere beauty I say nothing—polariscopists know what this is.—H. P.

[4127.]—MOUNTING CHARTS.—Any kind of cloth will do, but brown holland is, perhaps, the best. This should be nailed tightly and well strained on a drawing board and pasted. The map or print should be also pasted and damped till it lies quite fiat, then place it on the cloth and press out air-bubbles with a cloth, lifting the paper at the edge to let the air escape when needed, and when completed, leavo the whole to dry, and when quite dry, cut round the map with ruler and sharp knife, and the map will come off in a perfectly satisfactory state. If to be varnished, do so with mastic varnish, whilst on the board, sizing tho paper first with weak isinglaBs size.—J. B.

[4128.]—SETTING JEWELLED HOLES is an easy matter, practised by many a workman who possesses self-reliance and a steady hand; it ought to be particularly useful to those who live in country towns. Finishers, and English workmen generally, being accustomed to cut hollows in wheels and pinions, and hold the graver in their own hands when using the mandrel, will And it comparatively easy, and certainly not so difficult as learning to cut a clean hollow in a "best" pinion. Of course, it requires a little practice, and more attention to one or two important details. The holes are bought by the gross and half-gross unset for English jewelling ready t;ct in brass. I believe, by sending to the manufacturer's or tool-shop the size of any particular hole or holes, they can bo obtained in smaller quantities, or of different sizes assorted. I should recommend the first attempts to be made in odd pieces of brass and steel, till the hand is fairly into it, before attempting to operate on a watch plate; these, if cleasly done, will serve some future time in English jewellings. The more precision and accuracy possessed, the better one is likely to suceed. Those who work in an anyhow sort of fashion should certainly leave it, and watchwork altogether, alone. The first and most important requisite is to centre the plate perfectly tiue to the hole to be jewelled; not that this is anything very difficult, but the accuracy of the work entirely depends upon it—the depth of tho pitching is altered if not absolutely true. It must also run true in flat. The plate is chucked up on the platform P P of a tool (like Fig. 2) in wax or shellac, worked with a bow or treadle, or on a Swiss or Eng'l h maudre'. When properly centred, the hole is opened to A A (Fig. 1), leaving enough substance to support the stone; tho socket B B is next turned out to receive it. This is also essential to bo fitted as closely as possible to keep tho jewel properly centred; for if at all loosely fitted, besides being liable to get out of centre and upright, it will give groat trouble to secure the Btoue by rubbing down the setting, and will never make a clean j»b. Tho stone is held while being fitted with shellac on tho end of a piece of wire. Tho tool to measure tho depth to sink the jewel is shown in Fig. 1. I do not know if this Is exactly what professionals make use of, but am persuaded it is something of the sort, and kuow it will do perfectly well. E E are two legs, of a convenient length to rest on tho plate or bottom of the sink cut out for tho wheel, and F a screw or round rod, fitting so tightly in tho bar as to allow of its being set as a gauge, and adjusted to tho hole to bo jewelled or replaced. The legs and bar can be filed out of one piece, or a simple bar, if both ends are supported on the surfoce of the plate, with F to adjust to the required depth. Sinking thej ewel to the exact depth i tho most

difficult part of the wholo operation, as it is easily sunk too deep, or tho socket made wider, thus spoiling Unfitting in the frequent retouches. When it is done, the plate is turned out a littlo way, flush, or nearly so, with the stone, to allow the groove C C forming the setting to bo made. This rim or sotting ^should be just thin enough to be easily rubbed down—if left too thick, tho stone is apt to get broken in the effort to set it; on tho other hand, it is liable to be cut too thin, or spoiled. The two or three tools required for rubbing down are

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oasily made when thcirpurposo is known, tho shape M edgeways N, will be found one of the most useful; n< points or cutting edges are required, but rounded off, and burnished or polished at the acting parts. The gravers or cutters can also be made, just as finishers do, to cut any particular kind of hollow. To finish off the other side, the plato is turned to the other side, and the parts D D cut away to the stone without touching any part It rests on, either straight or curved, and polished. Tho above is for foreign work, where the jewels are set directly into the plates; the English jewels aro in separate settings, which arc fitted into tho plate, and secured by two Bcrews—G represents one. They are net in their settings exactly as above described, for which purpose the platform P P is taken off, and a piece of round brass fitted Into the socket S S, the screw T will hold it firmly, the point is turned to a convenient shape,and the brass to form thesctting waxed on. Tho continuation of the tool at R bears simply an English slide-rest; tho platfurin is adjusted after It is brought either outside, as represented, or in the socket S. It will sometimes bo found necessary, in foreign work, where the plate has Leen spoiled and a jewel cannot be found large enough, to set one in brass, and that as if it were a larger stone. The holes without endstones are set from one side of the plate, and those with from the other, or that on which the end-stone is screwed on. H is the tool for sinking the screw-heads, I and L tho end views, which, I think, can be made to cut sufficiently with a slittiug-flle; it can have a collet K fixed with a screw to sink any depth, or a shoulder turned on the drill itself. The magnetized balance is a sad job, and I can only confirm what H. Chapman has said, with the addition that it must not bo placed in a drawer with any tools, or any other parts of watch work. It is much to bo regretted that nothing has as yet been discovered that will demagnetize steel so completely as is required in horology. It wonld form a fair field of research for our electricians. I cannot understand why the watch should lose so much. If the hairspring were infected, two or more coils would adhere together, which would either make it gain or stop it altogether. It must be a horizontal watch, and both the wheel and the cylinder magnetized—if very strongly magnetized, would stop it. li* such should bo the case, there is no other resource but to replace the affected parts.—Nobody.

[4156.1— AQUARIUS.—Try a work by Sir William Fairbairn on water-wheels. I believo he is the best authority. Messrs. Spou arc tho pubUshers, price -is., sewed.—J. G.

[4156.]—BOOK ON WATERWHEELS.—Fairbairn's "Mills and Milhvork " is perhaps the beat.—As AssoCiate Op The Royal School Of Mines.

[4159.]—VINEGAR.—I submit the following method for the preparation of vinegar to "E. H." {No. 4159, p. 358), known as tho rapid process, now followed on the Continent to a large extent. A mixture is made consisting of 1 part of alcohol at 80 p. c., 4 to 6 parts of water, and 1-lOOOth part of a ferment, Buch as vinegar, honey, or the must of boor. A barrel with holes drilled in the middle and upper part, is then packed with twigs or shavings of beech, which have been soaked in strong vinegar. The mixture above mentioned is then warmod to 75- or 803, and made to tricklo slowly through the holes of the barrel upon tho beech twigs or shavings, thus exposing an immense surface to the air. The temperature of tho fluid rises rapidly to 95* or 106°, unless too small a quantity of air bo admitted. When the mixture has been passed through the barrel tlrae or

four time«' it will be found sufficiently rectified toiflat of decautfttinn. "E. H." could favourabh pars* -lta above process on a small scale, as from nparira*! find it yields a vinegar Admirably suited for doa^ and culinary \>aqm .- . Should the supply «i oxwnthat is air—bc| deficient, much alrfchtd* u profe which from its volatility ii carried off'a*'a vapour ir'-' lost. Any aromatic substance, essential oik or rwwood vinegar contaminated with kreo-ole, will un* the progress of ace till cation.—Waltfji J. KiaoLU'

[4160.]—KILLING MOTHS.-If "J. C. S," or » correspondent, p. 381, will try the following. I fodo» vinced they will at once abandonee chloroform, at! water, carbonic acid gas, and benzine methods of kfllifcmaths. Procure one ounce of cyanide of potawiiui.i little plAster of Paris, and a Bhort, wide-mouthed, w li'in. stoppered bottle, then mix the plaster of Pari* wiy water to tho consistence of thick cresm. and poor it ne the cyanide to the depth of Jin.; when set, cat oca; t». or three discs of thin note paper, somewhat largtr ;ir the inside diameter of the bottle, and press them don on the snrface of the plaster of Paris, and your appanis complete, compact, and in every respect c* veuient for killing moths and butterfles. It will ik remain efficient for a couple of years or more, ni the moths may, if required, be left in the bottle lot woeks' when they will be found in a relaxed state lot setting. I have just placed foar large flesh flies, Sfvtt earnaria, in my cyanide bottle, all of which were deadii twenty seconds, which is about the tune required to hi a large moth. Two of the flies returned to life aft^r re maining in the bottle ninety seconds. It is desirable, however, to leave moths in the bottle for a ampler hours before they are taken out and set. Entouioloci5t-. In their rambles, will And the cyanide bottle a moft'i ful companion.—Cyanide.

[4160.]—KILLING MOTHS, Etc.-I notice several brethren of the "net and pin persuasion" have (pfeo "J. (..'. 8." information on this head, bat neither seemto have used liquid ammonia. I find it has the gru; recommendation of leaving ita victims beautifully p laved for setting after death. My plan is first to stapef', specimens with chloroform and then transfer them for :.n hour or two Into a jar (in sejwrate chip boxe*) into which has been previously dropped s piece of filter paper saturated with the liquid. For green insects it M ill not do, as it bleaches them. Pru*sic acid sod chloroform make specimens too rigid /or easy setting,—

AUTOMEDON.

14171.]—BEES AND BEEKEEPING.-" Payne's Bee Book" is published at SO, Paternoster-row. price id. 1 don't have any entrance in the hide ot the cap of the hive. Let the hole in the top of the hive be aboat Siu. square ; placo on this a piece of perforated zinc, holes 3- 10th H of au inch; no other tised holes hi the zinc Mid be used. I use old tea ehesta for caps 9in. MiusTeand llin: deep ; cut a hole in the top aboat tin. sqanre; m thin place a piece ol Rum. ^o difficulty will be tond in removing a cap or box ot honey, as no broidmu M there. Follow Pavne's instractioT»,_p8.Rt 16.-*. l»«

[41780 -MALLEABLE CkST IWSN.-CmflutPmj^ "Metallurgy," vol. ii., on Iron andalecl Also UwiW*ciflcatlona of pateuN takeu out under th\shead; tae^> may be seen at the Patent Office. To tender caA-iw* malleable the articles are imbedded in powdered BUM (i.e„ iron ore) or hammer scale, andheated lor awrmj time; a reaction between the oxvgcn ol the ore ana «■ carbon present in the cast iron is set np, cart-nun *iu>;dride is formedand escapes. The cast-iron is tho* tmr«\e*s decarburized, a more or less soft Iron.»!■•••£ it is not truly malleable, it will not weld, but nay" dented bv a blow from a hammer. lB*^rjTjS made in this way are termed "run steel" article*. ■ Associate Of The Royal School or Mises

[4194.]—PHOTOGRAPHY.—STAINS, ir.-''^^ can remove the stains produced by the silver "JVjr by means of hyposulphite of soda or cyanide M^ shim.—An Associate or The Royal Bcbw* Mines. , . . . *,

r419H.]— GAS COOKING.—There is ft mistake »w statement of quantity of gaa consumed. It sh'ittw -■ for a small fruit pie, from 2ft. to 2$tt. tor a urge paaj potatc.es, or other vegetables, 2It.—not 2ft. per II *"as stated.—Thos. Klktcheb.

[4204.1—DRAWING PENS.—In reply to "T. jt,"» failure in tho use of his drawing pen may resui' i ■ three causes—viz., first, from a bad pen; M«JK the ink being too thin; and thirdly, by ■"■"JaT, much space for the flow of tho ink. ** vJSed beginner, I would advise him to purchase a ••EL liquid drawing ink, which will cost only one sfiu^ this will save him much timo and trouble.it beinRw ready for use when required. Now, as to the 'J**.1' t pen. When you are goinjf to work, sec that '■'vS of the pen is clean and bright (remember, if " j*T'j the ink will never flow properly), then open ***'£, t very slight extent, and with a pen, or still D***^ camel-hair brush, put a small quantity of ink H* pen, then close it till the points just touch. **5K is ready for use. After a little practice he will"V difficulty whatsoever in using it. When he eomi^ to study the proportional compass, diagonal L^' universal scale, Ac, let him, if ho can, call on Q"; A I shall be most happy to give him all the instruct^'may neod.—Thomas S. O'connor, Wrexham.

[4204.]— DRAWING PEN.—As I understand "£,[, his fault lies is using too much liquid Ink, in*U' .

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tho smaller rod ¡sonough for any average man to manage properly. A reel about 4in. in diameter, with about tiO or 1U0 yards of eight-plait dressed silk line; a gaff, with a handle Git. long, a few different kind -i of flies, and a basket into which to put the fish, will complete his ■equipment. As to his own wearing apparel he should

?rc: a pair of waterproof boot» with tups tu come above he knee. I would not advise him to make his rod: he can boy one cheaper and better, becauso the wood will be mora likely to have been properly seasoned; indeed, I doubt very much whether he can buy the wood in a fit 11'iulitiou. One bit of advice I will give him. When the fish has taken the fly, don't strike till he has really got it,or till he has turned to go off with it; then strike, anil strike hard, so as to be sure to drive the hook in over the barb. 50 рог cent, of fish are lost through neglect of this point.—J. McF., Stobo.

[4229.]— WASHING MACHINE.—I herewith sendyou a sketch of the most simple washing machino I have веоп. I think perhaîH it may be the kind of thing your correspondent ■ J. W." wants. I shall be happy to give any further information on the subject that may be required. Tho cost if inado by a carpenter would be about ¿2 10s.

Description.—Fig. 1 Is a section through tho middle of machine. Fig. 2 Is a Mide view. In each case tho dotted lines represent tho beater. Figs. 3 and 4 are front «ml side views of boater. The bearings are cast in gun metal, and the heater is made of ash.

HAND PLANING MACHINE.

[4233.]—KANSAS.—The faro from Loudon to Liverpool is 12s. Bd.: from Liverpool to New York, by steamer, £0 6s.—by sailing vessel, £4. Passengers can also bo booked from London at the same rates. Railway fare from New York to Kansas City is Ü3 lös. ßd.f While on this subject, I wonld say the society mentioned in my letter, the "Working Mens* Co-operativo Emigration Company," whose office la at the Mission Hall, Darlingplace, Milo End-gate, will be sending out a party about the middle of August.—3. D. Rogers, Hon. Sec.

14211.1 — OIL OF BRICK.—This is obtained by soaking common bricks in oil, and afterwards di.-tilliun tho oil from them at a red heat iu an iron alembic.—Hahby G. Newton.

[4211.J—EQUISONANT FLUTE.—If " S." can cull at 8o, Percy-street, Tottenham Court-road, he will obtaiu the information he seeks; or he can write to Jno. Clinton, Esq., at the above address. If he is an advanced player, and aims at proficiency, no matter what flute he selects, I strongly recommend the dally practice of \, .chin's " Twelve Grand Studies."—Sable.

[4348.1 — SILKWORMS. — Tho length of filament usually produced by a cocoon is about 300 yards, although iu somewhat rare cases this has been doubled. For one pound of silk eleven or twelve pounds of cocoons are required, about 250 of which go to a pound, therefore an ounce of silk would inquire about 130 cocoons. The other information may be obtained at Covent Garden Market. —11л кк Y G. Newton.

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Of Use.—Place the beater in its place and aolothes in each side with enough soap-water to » machine, then work tho beater backwards ■ -F. M.

[4351.]— HAND PLANING MACHINE.—I send encraving cut out ef Cook's catalogue. It is described thus :—•* To plane 12in. long, Bin. wido, and 61u. deep, self-acting croes elide; screw clamps; screw keys ; and six tools ; mounted on a cast iron buso for handwork, only £3S lus. Without self-acting cross slide, loss £7 10s. Parallel vice with circular plate A'7 10s. Ditto without circular plate, A'5."—T. K. P.

[4233.:— BICYCLE BREAK.—The ordinary furra of hreik is the proper one for rubber tires. It does not appear to wear or injuro tho rubber in the slightest tlogree.—Thos. Fletcher.

[4234.]— SEWING MACHINE IRONWORK.—Reduce with tho file any very rough parts (such as what I would call the " seam " of the casting), and give it two or three coats of coach-painter в' varnish. Price, Is. Od. per pint. Proved.—Aqon.i.UH.

[4387.1—VINEGAR.—I,rt "Grocer* do nothing so simple as to try to turn wine intu mult vinegar: oneumftlt* mont in your columns would secure him sufficient orders to álepOM of a large quantity of his genuine white wiue vinegar.—W. H. C.

[4248.]—SPARK FROM INDUCTION COIL.—The only way to find the length of spark It will give is by experiment.—Thos. Fletcher,

[•1250.]— ALGEBRA.—I wiH endeavour to give A. Pavios as little work as possible; but he must understand that he will now and thon como across passages, which he must omit through not understanding the principles to which they refer. This will not often be the case however, and if I knew the edition of Todhunter's differential calculus which ho intends to ом, 1 could easily point out anything which wonld be better passed over on a first encounter. It is only necessary to know algebra as taras quadratic equations, with a fail' knowledge of the theory of indices. The student must abo be able to use tho binomial theories, though he need nol trouble himself with the proof of it. He must also read the chapter on exponential and logarithmic series In trigonometry, ho muy omit tho chapter on the proportiOMl part*, and chap, xvii., &c, to the end of the bonk. Conic sections he ought to be well acquainted with. I moan analytical conias of course: geomotric conloe will not help him at all. As almost nil the ap!>!мч1 example* of the calculus are taken from oonlfl lions.he will find R almost impossible to proceed with out a good knowledge of this branch of mathematics. I must warn him that be will find it exceedingly difiicultto

read such a subject as the calculus wiihetut assistance —R. P. T.

[4350.1—MUSHROOM CULTURE.—After the horse manure (or droppings) has been kept in a heap for about a week or ten days, and heated to a certain extent, have it spread out in the open air to sweeten and drive olF the ammonia. If there is a hot sun and nice drying wind, three or four hours will be sufficient. You may then pat it together to make your bed, treading the manure thoroughly all tho time (you cannot make it too solid), until you got a depth of 18in. to 2ft.; upon this place your spawn. Cover this spawn with good damp mould to the cxten t of about 2iu. Again tread this, and make it tolerably solid. By this simple method on a bed 7ft. by 3ft. in an ordinary atablo or outhouse at a temperature оГд5Г» to 60°. I cau produce and cut mushrooms of the finest quality.—T. Pearson.

[ 12 Л.]— TODHUNTER.—Todhuntcr says (page 10) "If r denote tho circular measure of four right angles, tho circumference is 2 w r .: the circular measure of

four right angles is ¿JlTthat is 2 w." Hence we seo that

r the circular measure of two rigbt angles is тг, that i* 8-14159265 Äc. Ac. The symbol w is used to oxpro-ts the ratio of the circumference to the diameter, because tho value of тг cannot be stated exactly. It will now be seen that 3*14159 &c. (огтг), is the circular measure of two right-angles, and that Todhunter is perfectly consistent. —J. R. Kendall.

[4353.]—TODHUNTER.—"The constant ratio of the circumference of я circle to its diameter is usually donoted by tho symbol ir; hence the ratio of the semi-circumference to the radius will also be denoted by *, and

the ratio of the quadrantal arc to the radius by —,■

—Hymer's Trig., p. 4. Note: The Hemi-ciroumference is 180°, or the measure of two right angles.—Anon.

[4256.]—NEW VELOCIPEDE SADDLE SPRING.— "T. L." in your last issue speaks of a bicycle be has sceu with the saddle spring carried beyond the guide socket, about 6in. over the front of the guiding wheel, the hind wheel being very small. I beg to inform him that it is not patented. The makers are Orme Brothers, Wolverhampton. The advantages are that the rider cau sit directly over the crank, and so obtain very high speed with loss exertion than when the saddle is further back, the small hind wheel dispensing with the drag which larger ones have for fast riding, I believe it to be the host principle of construction yet adopted. — Thos. Smith.

[4264.]—MATHEMATICAL.—Multiply together the height, the breadth, and the moan depth, which in this case is half the height. Multiply again by 62$ (tho ■lumber of lbs. in 1 cubic foot) and divide by 2240 to reduce to tons, thus :—

18 v 11 x 9 x 621 ШП78

Ш) = »ST ««4 toas.

What is called the''centre of preseure" is at 9 th-> depth, or 6ft. from the boltom; and is where you should apply a beam across a sluice to support it in the purely theoretical case of having that beam and nothing else for a support, and it is actually the place where so mi sluice gates uro hung on horizontal pivots, so as to turn over of their own accord when the depth increases beyond a certain point.—J. K. P.

[4371.]— TRIGONOMETRICAL DIFFICULTY.

3(8log. 8-1) +■ i (4 log. 3-2)- 5.(2 log.) + 1J
5 4

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