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of onr conntrymen. You are becoming, if indeed yon ore not, as Mr. Ratty (of Manchester) says, already, "aii institution." I have been casting my eyes about to нее what other scientific journal you are likely, to absorb, bat as I do not know which are weak or which are strong, I will indulge in no speculation on the subject, and conclude by cordially congratulating yon on your deserved success.

A Benefited Subscriber.

THE LINK MOTION.

11041 Sin,—I find in your paper of July lstja 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 contradicts Mr. В., to carefully examine Mr. B.'s diagram of the link, in your paper of Juno 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.

to the soloist, enabling him, as they do, to produce those dashing and sparkling effects so charming to the ear. I know " personally" that the Boehm flute has them to a great extent—in many passages they are indispensable to its system; but tho Equisonant 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.

The 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—Revo d'un Bal," are enough to establish his fame, to say nothing of a host of original works of wliich his reviewers have said sufficient. He lived but to see tho only prize medal awarded to his flute " for improvements on the system of Herr Boehm," his early colleague.

Sable.

[graphic]

Throw of excentric .. .. .. .. 51"

Advance of excentric 1

Length of rod .. .. .. .. .. Б* 1"

Length of link .. .. .. .. .. 1' -1"

Lap of valve ¡"

Lead of valve J"

I send for Mr. H.'s 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 Щ inches. James F. Ryan.

P.S.—A great many of your readers are 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.

1105] Sir,—Pray suffer me to thank "Jnetitia," page 376, 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 »>'on enter the lists in. veritatis et jiutiiiiE сашат. "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 he inflicted on Mr. Clinton's memory. "Justitin" has left me little to add in favour of the Equisonant. Personally I know thU of it. Its tone is beautiful if it be /airly elicited; its notes are equal in strength, tune, and firmness, and its groat recommendation to flautists of the Nicholson school is, that its scale of fingering is natural, differing во littl.- 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 tho great value of " harmonics"

POWERS OF BLOCKS AND STRENGTH OF ROPES.

[106] Sir,—I enclose a few diagrams of blocks and tackles which might be of service to many of our readers requiring such mechanical appliances. This subjoct 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 single 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 the length suspending weight.

And further to illustrate the principle of gaining power by blocks, Fig. 1) 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 the line. The figures in the illustration correspond to the 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 :—

W. Strain
4*5 cwts.
6

8-1 % 102 „ 12-9 „ 18 22 One third of this sum in гоня is breaking strain. Say a pair of blocks two and three sheaves with lfc in. rope, what is the working power and breaking strain on blocks and fold? On table working strain is 10"2 x Б = 51 cwts. working strain on blocks, and divided by 3 is 17 tons, breaking strain on blocks, and this divided by 5, the rnunber of folds, gives 8*4 tons as breaking strain on fold. J. Hovell.

[table]
[table]

ACCUMULATING AND UTILIZING POWER. [107J Sir,—Will you allow me space to make a few remarks npon 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 means nf horse or wind, as to be available at some future time. I shall not attempt to answer such, but will btate what I heard in the River Plato (Buenos Ayros) in 1857. When locomotives were first introduced on tho 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 tho machine? where do you pnt them?" and when the eteam was issuing from the funnel, a cry was set up it was "white magic." There are such objections as your correspondent points out, attending the cost of coal* but to wait until the plantations are large enough to supply the fuel 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 accmimlrtte 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 such is not at all to be depended upon. I have crossed the "Somberombom" when my horse could skip across, and in a few months I have ridden fifteen miles through water before coming to the same river. Having spent several years in this country I am enabled to speak from experience.

I shonld 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, than coal.

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flOS] Sin,—Perhaps some of your correspondents will give mo their opinion respecting fast or moderato 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 you lose your colour, also your length. 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 I am hard of believing in. But, as I say, perhaps some of your more intelUgent correspondents may give me their opinion respecting it. Also, what length should yon have я silk for (say) six pairs of stones grinding (say) four bushels per hour.

A Subscriber.

THE SUN'S PARALLAX.

[1091 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, аз 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, &c., &c, "Hugo," I submit, is bound in honour to give by actual calculation what he considers the "true" mean parallax of the sun, because he has said that wliieh has been given by " Veritas" is not " true ;" otherwise, how does he 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 FBOM COEEESPONDENOE,

GAS.—" J. G." says:—"Ido not heme vor agree with

vour correspondent's remark that, 'Carburettmg Gas'

w at present nut a practical process. The Com

misionera of Sowers fur the City were so alive to the

¿tcaefit derived by sach process that they ordered 1800 to

be titled to the street lumps according to the principle

of Mr. |J. Ridd finding a saving of about 30 per cent, by

thoir adoption. Mr. George Glover, the gas meter

raau of act are r, abo proved tue benefits to be derived by

their adoption, the illuminating power caused by their

introduction was about 43 per cent. Tue Midland

Railway Company have had them fitted to their pendant

lamps at the new station at St. Paneras, beside which

numerous private firms have adopted this improved

t-ysteui, thus proving that your correspondent's remarks

are not tenable."

CURIOUS QUESTIONS.—"J. B." says:—"In reply to R. Gould s first question (page 878), there will be no iifference because the ball, atmosphere, and all else on the earth's surface partake of th<- earth's motion, " orbital" andárotatory, which consequently in no wise affect the relative motions or positions of such objects and the ■earth inter ее. Secondly, if the word 'space ' is intended to mean • as measured on the earth's surface,' there will be no différence, but if it be taken in any other seuse the difference will be so much, plus or minus, as may be caused by the earth's motion during the flight ot the ball."

TRADE AND COMMERCE.—" Sigma" concludes a long and elaborate letter on this subject thus:—"Last and most crushing of all, we have had five-and-twenty years' 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 years agi*, what the total income or even the average income oí the nation? If free trade is a losing game, gradually impoverishing us, how were our railways made; where did the shipping come from which covers every sea; whence саше the capital sunk in establishing colonies for our extra numbers:' lu 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 the present and twenty-five years ago. Look ou this picture and on that, and verily if these results bo the inevitable consequence of aunual loss and impoverishment, then, bat only then, is free trade a failure."

POWER LOOMS.—"J. W." says :—" I hope shortly to be 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 view of exhibiting the machines and ot arrangiug some licensee."

EEPLLES TO QUEELES.

[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. Tbe reason being that the law of " maguotism" which seems to Ъа the only form in which it can bo employed is that thsforco varies invcmely tlu «qttare of the distance from the magnet, which obvioualy reduces its available power to within exceedingly narrow limits and consequently almost forbids its use as a mechanical power.—J. B.

[3642.]—FISHING RODS.—" A Young Tyko " requires hintshow 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. 1 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 Tyke" had any idea what it would cost him for the mandrels, or triblets, on which the ferules must be hammer hardened (or their mouths will become anything but musical trumpets), 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 them In a suitable wooden pillow-block, which I had to make for the purpose in the lathe), and the time it takes an amateur, who is seldom so much of au expert at such operations as even my humble self, to do this work he would thankfully receive my good advice, "ЛопЧ"—and not set to work on operations as little worthy his time as grinding specula, or lenses for O. G. s and eyepieces, would be worthy to occupy the time of an observer like our "F.R.A.8.", which I suspect might be more nobly uud worthily employed in rmewing "The Fuel of the Sun," or viewing that luminary himself. Some advice I tender. Don't make а rod, or have one made— unless it is tobe only one of several rods—so short as five yards. Make it seven yards while you are about it, and havo two extra short extra butts made to it, one to receive its largest joint, and the other the next joint. You will have, supposing the rod has five joints (never havo more), seven yards; six yards, and four and a half yards, quite sufficient variety for all purposes. The beet 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 sufficiently long and taper to make a first rate top a yard long.—Тык Habmonioüh Blacksmith.

[3643.] — IBÓN PRISM,—Original size of prism is 3ft. long by gin. wide, and deep plate required will be 54in. square by Un. thick.—J. B.

[2643.]—IRON PRISM.—If I understand the question aright a square prism of iron containing 2,916 cubic in ches ig to be flattened into a square plate of uniform thickness, containing the same number of superficial

inchos, requirod the size of iron plate. Therefore ,s/2916 = 54 inches =sidc of square plate 1 inch in thickness.—Habry G. Newton.

[2643.]—IRON PRISM.—How cana superficies which consists of square inches bo equal to ¡solidity, which is а cubic measurement. Also what has the shapo of the prism to do with the form of the plate that has to be made out of it, which latter we are told is to bo square and of uniform thickness ?—J. K. P.

[2652.]— SULPHATE OF ZINC—Extract. "Sulphate of zinc, or white vitroL ZnO.SO* + 7HO is prepared by dissolving the metal in diluto gulp juric acid, or more economically by roasting the native sulphuret or blende, which by absorbing oxygen becomes to a great extent couverted into the sulphate of oxide ; the mineral is then thrown iuto hot water and the salt is obtained by evaporating the clear solution. This salt closely resembles sulphate of magnesia in appearance, it has an astringent metallic tnste, end 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 aud ammonia."—Hahky G. Newton.

[2668.] — SKETCHING FROM NATURE.—At Johnson & Sou's, 18a, Basinghall-street. Acetate of cobalt, 2s. 02.; muriate. Is. tid.—R. Sedöfield.

[2077.]—HYDROGEN GAS FOR BALLOON.—Many more details are needful to enable a truly correct answer to be given to this query. The weight of the ballon, thu height of the barometer and the purity of the gas must be first ascertaiued. lîut assuming the gas to be pure, its specific gravity is 0*50."> as compared with one of atmospheric air, consequently 1,000ft. of gas will support iu air 4l*3991b., and ii your correspondent will calculate on this basis the number of feet of gas which will lift himself and his balloon thö weight of which last he must assume or ascertain, the cube root of that quantity divided by 3*141 will give him the radius of the spherical balloon which will contain it with sufficient accuracy for his purpose^, which I venture to presumo are not practical.—J. B.

[2684.] —ENGINE CHIMNEY.—lam of opinion that a ohimuey 35 yards high having a flue 3ft. in diameter will do the work required by " A Subscriber."—K.

[3716.]— BEL ACQ ÜERING BRASS WORK.—Brass is dipped by passing it quickly in and out of the nitric acid. If the action does not takeplace during the first second the leaving the articles in longer only turns them black. The process should bo 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, aud immediately wash them in a pail of clean water or hold them under a pump. If not quite clean after the first dip scrub the part again, and put through tho process a second time, only remember that the oftener they are dipped tho 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. Tho quicker these processes are gone through the brighter and better the work will become.—Wai. Holmes.

[3716.]— RELACQUERING BRASSWORK.—In the first place, if the brasswork is jvery dirty, and not come clean enough for the acid to act on, it should be left in the acid for some time, then dipped in fresh acid; but before behiL; dipped iu tho fresh acid, he must take care that all the dirt is removed before being dipped again. The reason of the articles turning black is because they are not properly clean beforo dipping, tho old acid will make very good pickle.—W. Seabuook.

[3726.]— CHROME BLACKS.—" For 101b. of wool or woollen cloth," boil ono hour in a solution ot 4oz. chrome, 4oz. of bittartratc of potash (cream of tartar); then wash out of this solution, and boil in a solution of lulb. of logwood for one hour.—R. R., Rochdale.

[37S8,3766Y] — 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 tune might by their friction expedite the process. The tubos may be filled by inserting the mercury by little and little into the siphon end aud shaking it so as to allow the air to escape through it, or tho air iu the tube may be rarefied by heat, and if the lower end be then plunged iu mercury, the air as it contracts in cooling will draw it in and this process must be in either case repeated till the tube is quite full, when it should be held upright so as to allow the excess of mercury to run off. For philosophical purposes greater care, aud more adjustment and calculation, is needed than can be explained in few words.—J. B.

[8781.] —PHOTOGRAPHY.—There aro 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 to call at some maker's, and examine one. The vertical developing-bath is never used nowadays: it is a wastef ululan. If "P. M.*' finds a difficulty in getting tho developer to flow over the plate, let him add to each pint, from one to two grains of common gebitine dissolved in a little warm water. It will then flow readilv, without streaks and markings, which are sometimes difficult toavoid without the gelatine.—R. S.

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

[3832.]—BURNISHING PLATE.—The tool he requires is an ordinary steel burnisher, which can be obtained ai any tool shop. He must rub the ecratchos well with it, and he will soon find them disappear.—W. Seabbook.

[3843.]—STEEL WIRE.—I did not answer " J. R. T." (3842) for tho worst of all possible reasons—i. e. because of mine incompetence to do so. I may 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 small bells only cost a fow pence each, and what he calls wire gongs have a very disagreeable tone.—The Harmonious Blacksmith.

[3844.]—ENTOMOLOGICAL QUERY.—Larva of Cosmia trapezina is of a dirty green colour, with its dorsal, subdorsal, and spiracular lines white and spotted with dark green. Let "E.N." bowure of the larva of Seopelosoma katellitia also. It ¡a 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 lino.—Automedon.

[3841.]—ENTOMOLOGICAL QUERY.—I send for "E.N." tho description of f.*. Trapezina(larva), as given iu " Stainton's Manual," vol.1, page258, " Larva greenish with the dorsal, sub-dorsal, and spiracular Нпсэ white; the spots black or dark green. On oak, birch, Ac, especially fond of other caterpillars," appears in May and June, abundant everywhere.—A. S. O.

[3840.]—STUFFED CANARY.—"Excelsior" can clean his canary by nibbing it with a piece оГ clean white wadding. Afterwards he 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 bhade with dry whiting.—Ig No Raht.

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

13358.]—HOLE IN EARTHENWARE JAR.—A hule may be bored by a common blacksmith's drill used lightly, aud it had better be not more than ¿iu.. after which the hole can be 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 u>t to strike so hard as to cause a crack, audthe point to bo kept moving from placo 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 вате acid, about oue part acid to eight of water, into which he must put some piceos of iron wire; he will find them turn a red colour. After leaving them about two hours, take them out, dry them, and lacquer them with red lacquer.—W. Seabbook.

[3873.]—BOOKBINDERS'GLUE.—The best method of making the above is to break the glae into small pieces; then put it iuto 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. Plast Ans, 55, Dale End, Birmingham.

[3875.]—BLEACHING POWDER.—Bleaching powder is made as follows :—It is a mixture of calcium hypochlorite, or chloride. It is produced by the actiou of chlorine gas upon moist slaked lime. The gas is passed in rooms, on tho floor of which is laid the lime -in. thick, which absorbs tho chlorine, and the powder Is formed. "When treated with a small quantity of a diluto acid, hypochlorous acid is liberated, and may bo 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 be 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 chlorine in the fibre of the cloth. The bleaching effect is therefore only visible after the goods have been 'soured,' or dipped in acid." (See Ujscoo's "Chemistry.")— 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 in 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 Seabbook.

L3J4LJ—MARKING.—The best way to apply printers' ink is аз follows:—Get a little cotton wool; tie it up in a little soft leather; put a little ink on it, and dab it on a fiat surface, either iron or stone, till it is spread even. Then dab it on tho type till it is inked all over; then press the typo on the article 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 wator, and so will leather, but if only a small size is required vulcanized India rubber will be found cheapest.—H. U.

[ЗЭ8Э.]—SCREW ENGINE FOR CANOE.—What docs "A Young Subscriber" moan by wanting 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 it, and what is the width? He says in his query about 2jft.—Я. U.

[3993.]—PASSAGE TO NATAL.—"A Cornishmau" will find that tho " best " way to get to Natal is to take a first-class berth on board tho mail steamer; the " cheapest" is to work a passage out. Seriously, there is a regular line of traders to Natalleaving London, and homight find a captain willing to take him for his labour and a money consideration.—H.U.

[3996.] — BOOKBINDING.— Brass type would be best for " Au Amateur ;" it requires great care, aud a deal of practice, to use single letters. Leather is all prices, from 2s. 6d. to 12s. per skin; calf aud morocco nre very dear; bookbinders' cloth, from 8d. or 9d. per yard.—J. Plastans.

[8999.J— CYLINDER.—If "Ixion " gave the sue and weight of his steam carriage he might expect some one to give him tho dimensions of cylinders for it. How it is possible to say what size they ought to bo without knowing tho work required of them I do not comprehend. —H. L\

[4007.]—CURING HERRINGS.—I do not imagine Mr. Baskerville islRkely to find a book containing any authentic directions for the process he requires, so I will tell him what I know about tho matter. Tho method of curing 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 11 bloaters" and "high-dried." Tho bulk of bloaters for the London market are simply taken from the boats and laid in barrels or troughs, with salt between each layer. After remaining in pickle 24 hours, they are hung up to dry in the smoking-honses, but they are not subjected to any large amount of smoke. They are ready for packing in three or four davF, and are little more than fresh herrings dried, with'just sufficient salt to keep them a week or во. The proper bloaters, although they are not kept in salt much longer, are really smoked over tires made of oak saw-dust (at least that is what should boused). They will keep some considerable time. The "high-dried," as their name implies, are kept iu pickle till they are thoroughly Impregnated with salt, and are then taken to the < smoking-room, and allowed to hang there till they are, so to speak, "tanned," in which con lition they will last a voyage round the world, and then be good. The Scotch herrings, and those canght ¡n St. George's Channel, are made into "kippers" in large quantities, or cleo are treated to rather too mach salt. The reason ot this is, that the fish having spawned, the roe would only act as a predisposing causo of putrefaction, although, strictly speaking, this does not applyto Scotch herrings, which aro turned into " kippers" lor convenience in packing, especially as they are then worth as much commercially as the others, and farmers buy up the "offal" for manure.—Saül Rymea.

[4012.] -WORM-EATEN ORG.«.' 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 erdinary price is 6d. the oz.—Saul Rymea.

(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 da not know that I can give " John Barleycorn " any hints which will be of any use to him, as he doubtless is already <m /ait at so much of chemical analysis as applies to testing for acetic acid. Cryitalt of acetic acid, like most, if not all crystals, will polarize, but only in the form of crystals. If "John Barleycorn" can.pcrsnade 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 orin fluid (glycerine answers well for many objects), and the two glasses (that of the elido and cover), should be thin. Tho polarizer must bo 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 be cut off twice in each revolution. This is polariscopy in its simple form. Most of the objects commonly viewed by polarized light are seen by this arrangement in a ghostly kind of light on а dark ground, and if colour be wished the nsc of a thin film of selenite is needful. These arc 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, bv 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, tho best. This should be ¡tailed tightly and well strained ou a drawing board and pasted. Tho map or print should be also pasted and damped till it lies quite flat, then place it on tho 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, leave 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 Tarnish, whilst on the board, sizing the paper first with weak isinglass 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 nseful to those who live in country towns. Finishers, and English workmen generally, being accustomed to cnt hollows in wheels and pinions, and hold the graver in their own hands when using tho mandrel, will find 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. Tho holes arc bought by the gross and half-gross unset for English jewelling ready set in brass. I believe, bv sending to the manufacturer's or tool-shop the size of any particular "holes, they can be obtained in smaller quanti

difficult part of tho wfiolo operation, as it is easily sunk too deep, or the socket made wider, thus spoiling Unfitting in the frequent retouches. When it is dono, the plate is turned out a littlo way, Hush, or nearly so, with the stone, to allow the groove С С forming the Betting to bo made. This rim or sotting ¿should lie jnst thin enough to bo easily rubbed down—if left too thick, the stone is opt to get broken in the ofiort to set it: on the other hand, it is liable to be cut too thin, or spoiled. The two or three tools required for rubbing down arc

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tics, or of different sizes assorted. I should recommend the first attempts to bo 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 jewelling*. The more precision and accuracy possessed, the better one lslikely to suceed. ТЬовс 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 the 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 Eug'i h maudre'. When properly centred, the hole is opened to A A (Fig. 1), leaving enough substance to support the stone; tho socket В В isnext turued out to receive it. This is also essential to be fitted as closely as possible to keep the jewel properlv centred ; for if at all loosely fitted, besides being liable'to get out of centre and upright, it will give great trouble to eecure the stone by rubbing down tho setting, and will never make a clean jeb. The stone is held while being fitted with shellac on tho end of a piece of wire. Tho tool to measure the depth to sink the jewel is shown in Fig. I. 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 eink cut out for the wheel, and F a screw or round rod, fitting во tightly in the bar as to allow of its being set as a gauge, and adjusted to tho hole to be jewelled or replaced. The legs and bar can be filed out of one piece, or a simple bar, if both ende are supported on the surface _of the plate, with F to adjust to the required

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easily made when thcirpurpose is known, the shape M. edgeways N, will be found one of the most useful; no points or cutting cdgeB are required, but rounded off, and burnished or polished at the acting parte. 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, tho plate is turned to the other side, and the parts D D cut away to tho stone without touching any part it rests on, either straight or curved, and polished. The above is for foreign work, where the jewclB are set directly into the plates; the English jewels oro in separate setting«, which are fitted into the plate, and secured by two screws—G represents one. They are set in their settings exactly as above described, for which purpose tho platform P P is taken off, and a piece of round brass fltted into the socket S S, the screw T will hold it firmly, the point is turned to a convo nient shape, and the brass to form the setting waxed on Tho continuation of the tool at R bears simply an English slide-rest; the platform is adjusted after it is brought cither outside, as represented, or in the socket 8. It will Bomctimes be found necessary, in foreign work, where the plato has been spoiled and' a jewel cannot befonnd largo enough, to set one in brass, and that as if it were a larger stoue. The holes without cudstones are set from one side of the plato, and those with from tho other, or that on which the end-stone is screwed ou. H is tho tool for sinking the screw-heads, I and L the end views, which, I think, can be made to cut sufficiently with a slitting-tile; it can havo a collet К 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 be 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 would form a fair field of research for our electricians. I cannot understand whv 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. IÍ such should be tho case, there is no other resource but to replace the affected parts—Nobody. [4150.]—AQUARIUS.—Try a work by Sir William 1-airbairn on water-wheels. I believe ho is tho best authority. Messrs. Spon are tho publishers, price 4s sewed.—J. G.

,,¿4í?6]_?9OK 0N WATERWHEELS.-Fairbairn's Mills and Mill work " is perhaps the best.—An AssoCiate Op The Royal School Op Mines.

[4159.]—VINEGAR.-I submit the following method for tho preparation of vinegar to "E. H." (No 4159 p. 358), known as the rapid process, now followed on thé Continent to a large extent. A mixture is made consisting of 1 part of alcohol at 80 p. c, 4 to 6 parte of water, and l-1000th part of a ferment, euch as vinegar, honey, or the must of beer. 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. Tho mixture above mentioned is then warmed to 75- or 80', and made to trickle slowly through the holes of the barrel upon tho beech twigs or shavings thus exposing an immense eurface to the air. The temperature of the fluid rises rapidly to 96" or 105r unless too small a quantity of air bo admitted. When tho

four times it will be found sufficiently rectified to allow of décantation. "E. H." could favourably pursue the above process on a email scale, as from experienc« I find it yields a vinegar admirably suited for dometli.aud culinary purposes. Should the supplv of oxr«n— that is air-bej deficient, much aldehyde; is produced winch from its volatility is carried off as a vapour ал J Inst. Any aromatic substance, essential oU, or even wood vinegar contaminated with kroosote. will arre,the progress of acetiflcation.—Walter J Nichoi Ls • [4160.]-KILLING MOTHS.-H "J. C. S." or vomcorrespondent, p. 381, will try the following, I feel convinced they will at once abandonee cluoroform hot water, carbonic acid gas. and benzine methods of killinc moths Procure one ounce of cyanide of potassium.* little plaster of Pans, and a short, wide-mouthed ai Ijin. stoppered bottle, then mix the plaster of Paris with water to the consistence of thick cream, and pour it over the cyanide to the depth of {in.; when set, cut out two or three dises of thin note paper, somewhat larger than the inside diameter of the bottle, and press them down on the snrface of the plaster of Paris, and vour apparat ш is complete, compact, and in every respect convenient for killing moths and butterfles. It will also remain efficient for a couple of years or more, and the moths may, if required, be left in the bottle for weeks when they will be found in a relaxed state for setting. I have just placed four large flesh flic. Vuwa carnarta, ш ray cyanide bottle, all of which were dead in tw-enty seconds, which is about the time required to kill a large moth. Two of the flies returned to life after remaining in tho bottle ninety seconds. It is desirable however to leave moths in the bottle for a couple of* hours before they are taken out and set. Entomologist--, in their rambles, will And the cyanide bottle a most useful companion.—Cyanide.

[4160.]-KILLING MOTHS, Етс.-I notice several brethren of the "net and pin persuasion" have given .7. С. S. information on this head, but neither seems to have used liquid ammonia. I find it has the ereat recommendation of leaving its victims beautitullv relaxed for setting after death. My plan is first to stupefy specimens with chloroform and then transfer them for au hour or two into a jar (in separate chip boxes) into which has been previously dropped a piece of filter paper saturated with the liquid. For green insects it will not do, as it bleaches them. Prussic acid and chloroform moke epecimens too rigid for easy settinn—

AUTOWEDON. =«.n.iuB.

[4171,]-BEES AND BEEKEEPING.-" Pavne's Beo Book is published at 20, Paternoster-row. prise 4d I don t have any entrance in the side of the cap of the hive. Let the hole in the top of the hive be »boat Ota square ; place on this a piece of perforated zinc, hole» 3-10ths of an inch; no other sized holes in the zinc ehouid be used. I use old tea chests for caps 9in. squire and Uto. deep ; cut a hole in the top about 4in. square. ■ on this place a piece of glass. No difficulty will be found in removing a cap or box of honey, as no brood will be there. Follow Payne's instructions, jage 16.—J. Lee.

[4178.1 -MALLEABLE CAST IRON.—Consult Percys "Metallurgy," vol. ii., on iron and steel. Also the specifications of patents taken out under this head: these may be seen at the Patent Office. To render cast-iron malleable the articles are imbedded in powdered mine {i.e., rron ore) or hammer scale, andheate.l for a certain time; a reaction between the oxygen of the ore and the carbon present in tho cast iron is set up, carbonic anhy-' dndo is formed'and escapes. The cast-ironisthus more or less decarburLrcd, a more or leas soft iron is produced; it is not truly malleable, it will not weld, but may be dented by a blow from a hammer. Inferior tools, Ac, made in this way are termed " run steel " articles.—An Associate Of The Royal School Of Mines.

[4194.1—PHOTOGRAPHY—STAINS, Ac-" W. О. С can remove the stains produced by the silver solution by means of hyposulphite of soda or cyanide of potassium.—Ax Associate or The Royal School Of Mines.

[4198.1—GAS COOKING.-Thcro is a mistake in tho statement of quantity of gas consumed. It should be, for a small fruit pie, from 2ft. to 2Jft. for a large pan of potatoes, or other vegetables, 2ft.—not 2ft. per lb. weight as stated.—Thos. Fletcher.

[4204.]—DRAWING PENS.—In reply to "Т. M.," hie failure in the use of his drawing pen may result from three causes—viz., first, from a bad pen; secondly, from tho ink boing too thin; and thirdly, by allowing too much space for the flow of the ink. As he is only a beginner, I would advise him to purchase a bottle of liquid drawing ink, which will cost only one shilling; this will save him much time and trouble, it being always ready for use when required. Now, as to tho use of the pen. When you are going to work, see that the inside of the pen is clean and bright (remember, if it is <lirty, the ink will never flow properly), then open the pen to'a very slight extent, and with a pen, or still better, a camel-hair brush, put a small quantity of ink into the pen, then close it till tho points just tonch, when the pen is ready for use. After a little practice be will find no difficulty whatsoever in using it. When he commences to study the proportional compass, diagonal scale, universal scale, &c, let him, if ho can, call on me, when I shall be most happy to give him all the instructions he may need.—Thomas S. O'connor, Wrexham.

[4204.1— DRAWING PEN.—As I understand "Т. M.," his fault lies in using too much liquid ink, instead of buying it in cakes and rubbing it for himself as required. The ink sold in bottles is gummy, and will not make fine lines. "Т. М." must expect to nave to replenish his pen continually (using a camel's hair brush for this purpose 1, as tho great merit of Indian ink lies in its power of drying quickly.—R. P. T.

[4204.]—DRAWING PEN.—The difficulties of which "Т. Ы." complains, and many others that he probably knows not of, will be removed by reading the second course of Binn's admirable work on " Orthographic Projection," and its application to mechanical and engineering drawings. See advertisement in the columns of our English Mechanic—A Draughtsman.

[4204.]—DRAWING PEN—Take care to keep the pen clean, drawing a bit of paper between the points when the ink fails to flow; and never let the ink dry upon it; there will then be no difficulty.—J. B.

[4214.] —SALMON TACKLE.—" Doncastrian " will find a rod of 18ft. or 19ft. the nioet convenient, although for very broad stroams 21ft, or ¡Bit, may be requisite; bnt

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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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