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what be might have vaguely guessed from the aspect of the crepuscular curve. "T. A." founds hie views 0:1 the admitted difficulté« involved in the problems presented by the sky and its varying lights. But bliese difficulties need not cause ua to Dliud ourselves to clear evidence of another sort. As for "T. A.*e" explanation, I must say it is too wild for serious comment. Ii, indeed, he could show reasons for believing either—1st, that iron, magnésium, До., can combine chemically with oxygen apart from the conditions which have hitherto been found necessary for such combination ; or—2ndly, that these conditions exist in the upper regions of the air, he will doubtless be listened to gladly by scientific men—always supposing those reason*» to be founded either on observation or on experiment. 1 do not consider the ordinary employment of the

{»hoto graph er to involve **a series of very delicate nvestigatione concerning the nature and properties of light," so far as the subject " T. A.* has in hand is concerned. All photography can teach on that subject is that the light from such and such parts of the sky lias at such and such times a greater or less active power. The conclusions to be drawn from this are by no means necessarily such as M T. A." imaginée.

R. A. Proctob.

FAIRY WHEEL8.

Sm,—After having read the letter, p. 233, several times, I cannot discover of what kind of stone those discs are made. If they were not so great, I might have taken them for parts of fossil encrinites, but "Subscriber" says none of them were the same size or thickness; they must then have been made by man, cut. Ac.; but for what ригрове7 Two suggestions present themselves. They were intended for throwing with tbougs, or lassoes, or for stringing them as a necklace, or wearing as ornament. Very ofteu pierced objects are found in caves, tumuli, Ac. Slight not these beads, Ac, forming part of necklace», have become, later, objects of exchange —a primitive money? Might it not be possible to trace by that means the communication ancient tribes had one with another? The note of "Subscriber" affords me the occasion of communicatiug this idea to my brother correspondents. I hope some other, more acquainted with the question, will bring also his stock of information. Meanwhile I quote a few examples, briefly, Mr. Editor, saying all notes should be drawn up as accurately as possible.

Pierced objects have been found in many excavations in France, Belgium, Ac, among what are called the remains of prehistoric times. A necklace of human teeth was found In Belgium; in North America, in the tumuli of Columbia River, Walla Walla, many beads, dentaliutt. necklaces, Ac, were found. One tumulus In Virginia gave 1700 grains or beads; with the Celtic warrior found in England, Bear Salisbury, were two fragments «f fossil encrlnite and a bead of pottery; a Celtic necklace, made of shells, was found near Dijon, in France; many Indians, negroes, Ac, have their shell necklaces; remark among them the cowries—in many places at the same time a money and an oruameut. The Egyptian beads, necklaces, Ac, of so many different substances, are well known to all those who have visited the British Museum. The Chinese have yet pierced metal discs for their money; the English Hong-Kong coinage is another specimen of it. I have said a word, in another number, about the whampum of North America, also a necklace and a money.

Bernardin.

COLOUR BLINDNESS.

Sir,—Concerning the remarks of "Anldtpot," in your last impression, I have little to say. I have never met with a person to whom red appeared black, and I therefore thought it undesirable to dwell upon that particular form of the malady, though I know such an abnormal vision is repeatedly to be found described in books on the subject, though it Is generally allowed that such an anomalous vision is only occasional, notwithstanding Sir David Brewster attempted to show that red colour blindness is most frequently to be met with, and that a normal eye loses its sensibility to red more readily than to any other colonr, and that a defect in the vision of any person will be most strongly marked when examined by red light. Though " An Idipot" makes no mention of the fact, I should suppose that the combination of red with other colours does not produce the same sensation of colour that a normal eye perceives. For Instance, in a purple the red is not missing, but it appears black, whence it is to be inferred that purple appears as a very dark blue. I would invite "An Idipot1' to make some further observations upon his anomalous vision, for it must be admitted that a colour-blind person is better ad apted to form a perfect conception of his defect than a normal-eyed person, and can more readily colleothis facts-, for let him (the colour-blind) be the inquirer, instead of the witness, and he mny collect evidence about colours In every possible shape, from the scientific investigations of the philosopher to the artless remarks of the child. He need not go far for an answer to any question he may choose to put, however abstruse; and as to common facts, almost every one he meets is a competent witness from whom he may gather them.

Omicron.

EMIGRATION.-TO "F.R.G.8."

Sir,—I am glad to see "Cotton Clerk's" letter in

the Mechanic for this week. Let me also appeal to •' F.R.GS." Will he kindly tell me if there Is any hope lor me abroad, and where, and how ? Although a clerk, I think I knowaspade, a hoe, axe,prong, Ac, when I see one. I am fast learning how many beans make 5, and can already see nearly as far through a stone wall as some people. I am a clerk 37 years of age, married, with 3 children, eldest 10, youngest б (both boys). We have saved a few pound*, and could realise я few more. For the last 3 years I have lived 4 miles from my work, I therefore know bow to walk. I have

had 110 poles of garden allotment and orchard under my hand alone besides my daily work and law work, accounts, Ac of an evening, insomuch, that I have often seen the sun rise before I went to bed. Pigs, poultry, bees, Ac,have also had my attention. I kuow French and Latin thoroughly. I may, therefore, be said to know what work i<*. both mental and physical. It is not so much If or my own as for the children's sake I wish to go abroad. I should prefer the trade of '* earth tickling- " to any other, belüg the only one I know well. Will "F.B.G.S" either pat mo on the back or knock me down at once in the matter of hope?

Hmlway Clerk.

THE "GERM THEORY" AND DEDUCTIONS TBEREFROM.

Sir.—The preat interest attached to the "Germ Theory " in any of its relations is my excuse for asking your insertion of this letter. It is an acknowledged fact, that on elevated lands of high altitude, 7000ft. to 8030ft. end upwards, the Inhabitants enjoy a striking immunity from may diseases, particularly from phlhisù. It appears also to be the case that a sojourn in such elevated rigions is a sure means of arresting any further phthisical development which might have bad its origin at tower levels.

These facts 1 have always thought most interesting, and well worth of investigation, but although I have continually been on the lookout for a solutiou of them, 1 have never yet seen a logical, or even plausible reason propounded. A considerable amount of investigation and attention to the subject—all the pros and cous duly considered, but into which I need not enter—has convinced me very strongly, or I may say entirely, that the "germ theory " would be found to account completely for the phenomena.

Cold is a well-known arrester of germ development and consequently of their physiological, pathological, and putrefactive effecte.but I have never observed it advanced that a rarefied atmosphere may be so also— although of course from quite different reasons— simply from the fact that air of great tenuity will net suspend the germs mechanically and carry them about. If experimental research proves this bypotbisis to be correct, I think it may be logically inferred that those diseases which never appear amongst the inhabitants of high altitudes, or are arrested in others upon going to reside there, are really due to, and sustained by, the presence of animalcular life. This is particularly self-evident I think as regards phthisis, and suggests the trial of a simple means for arresting and curing that dreaded disease.

I propose 11might be done either by filtering the atmosphere thoroughly before inhalation—much in the way some of Professor Tyndall's experiments suggest—or otherwise, rîr-ч heating the animalcular air (to a degree sufficient to destroy the vitality of the germs, and consequently multiplying their morbid action) and then cooling previous to using for respiratory purposes.

Taking for granted that the practical correctness oi my theory Is demonstrated, let me by way of illustration, suppose that such a building ae the Palace of Sydenham, for instance, were applied for utilising it, when hundreds, nay. thousands of invalids could live comfortably and pleasantly together for some months, being all the time qntte eccluded from the—to them—morbid atmosphere of the outer world, and that thin air supply was treated, previous to introduction into the building, in either of the ways I have suggested. I think the same constitutional effects would be found to be produced—and for similar reasons—as already by a few months' residence at hig_h altitudes. A similar arrangement, and for a like object, migbt be carried out in hospital practice. Such experiments as would placo the correctness of my views beyond a doubt are entirely beyond my power.

This being во, my object in bringing the matter before your readers is that, perhaps, in the event of their thinking my ideas worthy of investigation, some of them will not only experiment themselves, and put the theory to the test, but also, it may be, advocate the matter amongst their scientific and medical friends.

With your permission, Mr. Editor, I beg to as к for a discussion and opinions of my proposal in the columns of your widely-known journal.

J M о.

BORING INSECTS, Ac.

Sir,—The notice on "Boring Insects," p. 170 of our English Mxchanic induces rae to forward a few lines on the damage sometimes caused by insects. I extracted them from several agricultural papers.

In 1832 the Hessian fly, Cecidomyia destructor, destroyed corn in the State of Maine, Vermont, and in North America, to a value of five millions of dollars.

In 1H46 another small fly, Cecidomyia tritici, caused In Belgium a loss of 92 millions of francs to the wheat harvest

From 1740 to '49 nearly all the meadows In Sweden were annihilated by the caterpillar of a pbalœna, Ска reas graminis.

In 178t> the small turnip fly. Halt tea »emorumt devastated in Devonshire to the value of £100,000.

It is said that in 1784, the wheels of a mill on the Severn were stopped by the abundance of cockchafers in the water, what may be the truth of that assertion, in our times, In 1866, In the Department of Keine Inférieure, France, the premium paid for the destruction of the larva? or grubs of the cockchafers was 18,000f., and the quantity gathered 160,000 kilog. In 18:5 the Department of the Sarthe allowed a premium of 30 centimes for an hectolitre, and 300 millions of cockchafers or larvsa were collected. In 1807, 6160 millions were killed in Switzerland.

The Bostrychw typngraphus, or "printer," committed from 1665 to 1827 incalculable depredations in the forests of the Harz, In Germany, and caused the stopping of the mine works, and nearly the total ruin of some villages. In 17S:s alone, 1,60 >,000 trece were destroyed. There arc actually more than ¿0,000 oak trees attacked by the scolytus in the Bole de Vincennee. The common elm ecolytus, Scoiytus destructor

represented, I think, on p. 176. last number, is known iu many places, destroying the trees In the public walks. For more particulars see " Die Forst Ineectin," ven Dr. Ratzeburg. 3 vol»., in 4to ; "Entomologie Horticob*," by Alph. Dubois, Brussels, 1865, 1 vol., In 8vo, with fine plates; "The Farm Insects," by Curtis, Ac, &c.

Bernabdin.

THE EARTH AND ITS FIGURE.

Sir,—la discussing any matter with such gentlemen as Mr. ßeardsley, it is necessary to adhere to one point persistently, and have it distinctly settled before passing on to another. Arguing for victory, and w"~ with a sole aim at ascertaining the truth, suoh a wri acts very much like a small quantity of water taiued in a bladder; grab It as forcibly as you is sure to elude your grasp, and immediately position to some other portion of the receptacle, and can only be fairly captured when it is driven up lichtly into a corner. .Mr. Beardsley, like all men of his stamp, never recurs to a shattered argument, nor, wheu he finds that an argument has been crushed by a reductio ad absurd Km, does he either try to rehabilitate It or acknowledge his f lluro. Thus, with reference to the explanation of the sun's setting by its getting beyond the focal distance of vision, whatever that means, he declines to answer the question as to how It is that the sun does not appear to decrease in size as it, according to his crotchets, increases in distance.

I wish to ask an explanation of a passage lu Mr. Beardsley's last letter, and to state a fact which will be something new to that learned astronomer. I refer first to a vessel homeward-bound. In the approaching vessel "the upper masts " and sails are, according to Mr. В., in focus. If so, how comes the bull to be ont of focus, for it is as near as the; sai Is (In fact nearer)? Again, how come the upper masts and sails to be apparently growing out of the sea if the curvature of the ocean does not intercept the view? Are we "to believe our eyes," aud that the hull and lower sails are under water? Or lastly, are we to believe that the sails have left the hull behind?

The fact I propose to state is relative to the passage. "The sailor Knows by the chart the relative position of one country or island to another." Now that Is just what, but for the invention of a distorted chart, conetructed on the supposition of the earth being globular, the sailor never could know from a plane chart. Mercator's chart is во constructed that, In order to preserve the relative bearing the distances are distorted to an unlimited extent, so that a new scale of measurement has to be be used for every degree of latitude, and even then it la only an approximation. Had the true distances of the places been preserved on the plane surface, the sailor would have found the bearings all distorted and pointed wide of the true mark.

Then, Sir, when Mr. Beardsley has made acquainted with the Mercator chart in universal use, he will explain to us why it is that we cannot draw the surface of the earth on a plane without monstrously distorting either the bearings on the distances. I may have something further to вау on the subject, but certainly not before.

[It is better that this controversy should now cea.se. —ÜD. E.M.J

F. H. N.

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EXTRACTS FROM CORRESPOMJENCE.

RUSHES. — "Bernardin" say*: — "In reply to 'Camelford,' p. 207,1 think he might do better to Inquire at a paper mill in his neighbourhood, or to the Editor of the Paper Trade Review, 97, Newgate-süeet, London, as I am not able to give him the particulars he desires about price, Ifcc. I believe rushes should be cut and dried, aud packed, во as to present the leva bulk possible."

I. W. WOLFE'S "ORIGINAL" CONTRIBUTIONS—" Vibrator" writes:—"! was rather surprised on looking over a would-be rival to find my method of trisecting published In No. 264, p. 89 of the English Mechanic, copied and contributed without any acknowledgment by a Mr. Isaac \V. Wolfe. If he wished it to appear iu that paper he might at least have had the courtesy to acknowledge whore he saw it, and not contributé it as the result oí his own researches,"

INDUCTION COIL,—ANSWER TO "SIGMA."— "M. G. Cunningham " writes :—■' Permit m« to oiler my best thanks to * Sigma1 for replying to my letter,

C. 207, I was quite aware of the theory he propounds, utat the saine time not quite satisfied about it, and ан my plan only involves a slightly increased bulk I think 1 will persevere with it. Experience has proved that division oi the coil by ebonite discs intensifies the current, and the reason is theoretically explained as 'Sigma ' puts it. Why, however, it it be so, employ covered wire, which is expensive, and far more bulky than plain, the only object boiog to insulate the layers t Varnish, paper, tissue or other medium could be employed with greater certainty than any silk coveringata tenth of the price. My coll, now at its 12th layer, aud working with four quart Bunsen elements, gives well-defined improvement as each layer is finished, and I think it will answer well; should It not, however, I will not be so thinskimied as to keep my failure from those whom it may iuterest."

TESTED RECIPES— "A.Bonghey" write*:—" A "Morayshire Man " ¡s quite right in his remarks about the above. Some time ago a recipe was given in the English Mechanic for ' brillantine.' The mixture cost more than what Is sold In the shops, and turned out to be a very greasy mixture, with а—uertalDly not a perfume—which would effectually prevent any one from using it."

THE "PHANTOM" BICYCLE.-"Donald W. Preston " says :—" I can recommend the " Phantom" velocipede wheels to your readers as the best 1 nave ha\e seen, and as fully answering their description in the advertisement. J. Tvdeman's unwarrantable letter made me hesitate in ordering a pair ; but now I have them, and can say that his description of the glasses can be easily removed for cleaning, flic. A hot water tank in the bottom heated with a small pas jet underneath will make a tropical store on a small scale, or я hot water, pipe round the inside, and a small copper boiler underneath will do егев better. I have one, and for two years have grown with success the rarest tropical plants, orchids, &c- One year 1 had orchids only, the next I had caladiums, Egyptian papyrus plant, dwarf palms, tree ferns. &c. Now I 'have aquatic plants from the Amazons and Borneo, pitcher plants, &c. It costs шс little or nothing, as the plants always increase in value, and I have no difficulty in exchanging them. So far as treatment goes, he will learn more from the persons he buys his plants from than any one else, us each plant has peculiar habits. The case should have a reasonable amount of ven* tilation, so there is no need for care in fitting the glasses and woodwork closely-, mine is open iio. at етегу corner all the way up, and we burn a large quantity of gas in the room without the slightest effect on the most delicate plants ; if they are quite close they get mouldy.—A Dentist.

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[ЙЯЙ.] —MUSICAL BOX,—1 must apologue to Harry Bertram for too severely criticising his description, which, however, I said was well repeated us Гаг As the lesson was learnt. И« encan» that the end of the roller has a flange which mores in the notch oí right lever. This may be the case in very common boxes that only play two tunes, and I do not think would act for three: and it is had, as it enables you to shift the barrel while playing, which has a bad effect, or crea to shift the barrel when not playing, which is destruction to the box. In good boxes it is done by a wheel of the same number of teeth or rather spokes (and no rim) as the number of tunes to be played, which is fixed between the barrel and the first toothed wheel, only fixed eccentrically near the outside of that wheel, and every time it is carried round by the barrel turning, one of the spokes is caught by a fixed stud, and is held by it till the next spoke comes to the right place to be itself caught by the stud at the next revolution of the barrel. On the boss of this spoked wheel is a short piece of a screw or a carab which keeps pushing the barrel further and further until the end of the camb is reached, when a spiral spring pushes the barrel back ready for the first tune again. The music is not stopped by the L-shaped lever dropping into the hole in the end of barrel, but when it does drop in, the curved arm shown in the drawing, p. 164, on the opposite side to the hook, catches hold of one fan of the fly and stops the works. It is a fan-fly not a fly-wheel, as it is not a wheel at all.—J. K. P.

£2639.}—OPINIONS WANTED.—Thanks to Mr. Harrison for his advice about the links and the eccentric. When the lever is in the centre notch the valve spindle end is in precisely the centre of the link, and the eccentrics are properly set, nut I think he is wrong when he eaye the link ought to vibrate on the centre without imparting any motion to either spindle or valve, for I have noticed several since, and they all work the valve a little, but not enough to open the perta, which is caused by the action of the two eccentrics one against the other. If our paper is an International Mutual /rtpeoccment Society I am surprised that the subject has not been taken up by more of its members.—John W. Brdpord. [ЙМО.]—GIRDER PATTERNS.—In "N.L.Vanswertomy query he says that making the pattern bent would not do much good, as the moulder would ram it ont of shape. Now suppôt« the girder to be 40ft. long, section as per sketch (Fig. b, bottom flange ft$in. thick, rib ljin. thick, how will he ram down the ends, and if he can bend it to suit his requirements is it not just as possible to make the pattern bent, and so save time, and with more surety, rar what is to prevent the ends from springing out again, as it would be moulded on its side? Again, a gutter of this section 28ft, long (Fig. 2), thickness at A Ain., and at bottom ¡in , which would be moulded on a block to fit the incide, how would he bend that, and what weight would he require on the middle to keep it down, as it would be

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moulded with the bottom downhill. And again a foundation plate 33ft section (Fig. 3) thickness of side А В С D Jiu., and the top l^in.,moulded with the top or round side down hill; «nd lastly one of a smaller pattern, a ule plate hearer for malt kiln floors of the same site (Fig. 4) section, thickness at point of web fin., A at ton В fan,, and thickness of top flange fein, and 4ft. 61n. long, which he might bend in the pattern with a Ы1 of trouble and some weights to keep it there ; hut which я -)ald he safest, his plan or to make the pattern bent? And tbsa be floishe* by saying that It is a question whether one

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¡KU er of practice is worth a pound of theory, but I think ¡ ran the manner in which he writes he has not got an ounce of к <iry with a proportionate less part of practice on that ■ ■ '>_:■ i. The above examples have all been cast, and the whole weal straight except one of the foundations, and then the pattern had tobe made a little more round. I hope this will be received, as sent, in a free open spirit.—John W. Bkdtord,

f2675.}-POLI.SHlNG РГУОТ8.—The ridges mentioned by it0*" ïTM Cftuaed uy the polisher having the side that polishes the shoulder too much inclined to the side that polishes the pivot. It ought to be nearly at right angles. Pressing too hard against the shoulders has also a great deal to do with it The polisher ought to have a side as well as a length motion given to it now and then, to cross the marks as it were. The bow takes long strokes, while the polisher move» very little-, and always contrary to the direction the pivot turns. "Cylinder " will do well to attend to the above; and I may add, in answer to his query, the conical pivot he marks В is used only for good and best work, in holes furnished with endstones. Cylindrical pivots with the ahooider bevelled off are for more common work, though I have never seer but once or twice a Geneva cylinder with

conical points, even in the beat work. Cylindrical pivots are the easiest to make, and in foreign work a Swiss pivoting tool and burnishers are used. Ail English pivots are made with a polisher. I have seen a brass centre used, the pirot laying full length' on it, but I prefer the point only supported. "J. A. E." uses the right word when he says 'catching " ihe centre. Ile must not file away all the broken pivot, but leave the mark where it was; he will find it much easier to catch the centre of that small ring than if he made the surface uniform. If he cannot mark the point exactly at once he must try to draw it afterwards to its proper place,— Nobody.

[3707.]—TWISTING POWER OF SHAFTS.—The relative strength of shales to resist torsion is as the cubes of their diameters, the description of metal being the same. The relatioe strengths of different metals are as follows :—

Taking cast iron = 1,

then wrought „ = 1-19

shear steel = 1*76

cast „ = 2 0;

and a shaft to he equal in strength to a cast-iron one, must

be. if of wrought iron — less in diameter, shear steel -85 'J

1 cast steel --.

8 Q. Q. R.

[3714.]—BOILER,—" One in a Fix," may stop the humming noise made by his boiler by getting twu sheet iron platee to fit each ash-pit. and having them drilled with a quantity of \'' holes ; the plates may be attached by hinges, or made to lift away when the ashes are got out; if he will try this I am confident it will cure his noise, having tested it frequently myself. Do not put too many holes in at first, but add them afterwards if the draught requires it.—J. B. CaossLEY.

[3786.]—AREA OF SAFETY VALVES.—The difference of the aieas of the flat and concave valves may be found as follows :—

Area of flat valve = 42 x -78¿4 = 12-5664 eq. in.

The area of the concave valve may be found by adding the square of the radius of the valve (-in.) to the square of the

depth of concave r°rt( —in./ and multiplying the result by

8 31416. Пспсе we have

2* + I _ | x 31416 = 13-0081 sq. in.

w

Then

13-0081 12-5664

0-4417, the difference of the areas of the two valves—William Moor, Jun.

[3717.]-COPPER COIN.—I beg to inform S. Smith that this isa coin of Emmanuel de Rohan, M.M. of the Knights of Malta. I am sorry I cannot give any particulars; should I be able at some future time I shall be glad to do so,—D. T. Batty, 9, Fennell-street, Manchester.

[3743 ]—SYPHON PIPES.—I thiuk "Calculus" will find that the quantity of water discharged by a syphon will be equal (or thereabouts) to that discharged by a plain pipe of the same bore nnd length as the syphon, and with a nead equal to the difference of level between surface of water in vessel or reservoir, and lowest end of syphon pipe. This ean be found by any of the ordinary rules for that purpose, and perhaps the following (I believe by Hawkaley) is as good as any :—

ft

С = 22БЯ V — x Г>з
С = cubic feet per minute L

L = length in feet —- ■ —

h =. height „ M D = diameter of pipe in feet. The dimensions and quantities are here given аз in feet, but will, of course, do just as well in inches, or any other unit of measurement—Q. Q. R.

[3744.]—SILVER COIN.—I think there are errors in the legends; the nearest approach to it is a silver penny of James 1st, which reads on obv. "IDG. ROSA. SINE. SPINA." andonrev.,"lVEATVR. VN1TA. I)EVS." If there is no mistake in J. Nash's description, the query must stand, but if otherwise, it had better be put right in your next.—D. T. Bavy.

[3745]-STEiM PIPE JOINTS.—I always úselos, of sal ammoniac to every lib. of borings, with just a dash of sulphur to quicken ¡tin hardening.—Anti-eqyptian.

[3746.]—TESTING BOILER.—It will beof no use of Thos. Edwards testing his boiler without he can see the surface and seams of all his plates. If his boilers are only single rivetted, he cannot work them at more than 161b. pressure. I had two boilers which I worked at 151b. pressure. I had my boilers tested to 1201b., indicated by Bourdon's pressure gauge; they stood it better than they could be expected, although they (the engineers) will not allow them to be worked with more than 151b. pressure, being single rivetted boilers.—Amti-Egyptian.

[3750.]—8ILVKR COIN.—"A Beginner" will see his coin in Ruding's Appendix, plate 39, No. 13. It is thus described, p. 300:—"Obv , BALDREI) REX. Head rudely drawn, Rev., + ETHEL..D MONETA. Double cross with an amulet in the centre. Bodlean Library." I imagine it to he at least scarce, if not very rare.—D.T. Batty.

Г3751.]—ASCARIDES.—"A Great Sufferer" should take half a glass of good port wine (not the cheap (!) advertised poison) every morning, fasting, for three mornings, then stop three mornings, after which repeat the dose. Tbis will cure him in a month, provided he is careful in his diet, avoiding fruit, and especially cake or pudding with currants. Proved. —F. H. ,

[3755.]- TURBINE WHEEL.—" Senex" seems to have asked me almost the same question as I have asked him, which was, what quantity of water and height of fall was necessary to drive an one-horse wheel. However, as near as I can get at it, the fall would be 20ft. through a pipe of Jin. internal diameter. 1 would also ask what height of fall or pressure of water is termed high pressure, as in some street mains ?—А. B.

[3757.1-A BOOKBINDER'S PLOUGH.—Enclosed is u Hketch on the scale of } of an Inch to an inch. A A ia the n.'.;h t hand oheek of the plough, lOin long by 4| high, i.'i thick; the left hand cheek 1* of the same di

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part is Ijln. In diameter, at the shoulder of the handle part It Is 2in., a groovea wide Is turned in the plain part, which allows the bolt D to pass through, and act asa sort of garterpln, to cause the two cheeks to recede from or approach each other ; the bolt D is of Iron £ square, and bevelled out to g square at the bottom, so as to grip the knife F, which has a iquaro hole, bevelled, to match the bolt. E le a nut, which screws down on a lozenge-sbapea piece of iron, so ns to grip the kulfe very tight. С С are two guide rods 13m. bug, i square, firmly fastened into the oheek A, the handle of the screw is Sin. long, as the knife cuts the handle should be gradually turned, so as to keep the knife to the work.—Ab Initio.

[3765.]—NAVAL ARCHITECTURE—" G. E. J." should write to C. W. Merrificld, Esq., (Principal of the School of Naval Architecture,) South Kensington Museum, who wilt give him any information he may ask for as to the evening classes.— R. M.

[3768.J—POISONING BY CANTH ARIDES.—I am very sorry to see "M. D." states in page 237, Vol. XI. that the effects of cantharides arc only transient, he. They are not so; in small doses it is an irritant of thebladder-, in larger or improper doses it produces serious bleedings often resulting in death. It is administered surreptitiously under the idea that it is provocative of physical love, for which purpose ■t is absolutely useless. No man conscious of his moral responsibility would ever administer it, exceptiug under and in strict accordance with the orders of a well qualified medical practitioner. 1 believe any person administering it for improper purposes is liable to a criminal prosecution.—E. Deacoit.

[3772.]—OLD COINAGE.—Old copper coins may he sent to the Master of the Mint, Tower-hilL London, who will, uo doubt, take them at, I believe, their full value.—R. M.

[8773.]—&-PLATE PHOTO CAMERA,-!/ "Snatch Block" will tell me whether he wants to make a portable camera, or one for the studio, I will tell him how I made mine. Of course, if the Editor, be agreeable, I could describe both, t-plate is not too small to begin with.—Mus.

[3774.]—LOOSE PULLEYS, Sec.—The best plan will be to bore the pulleys about gin. larger than the shaft, and sweat a brass bush in it, or one composed of the following alloy :— (Babbitt's metal) tin 10 parts, copper 1, and antimony 1. I have proved the latter to be a very good wearing metal.— Staem.

[37741—LOOSE PULLEYS, be.—Wm. Corlett should turn the shaft end true, then bore out the loose pulley, and let the pulley work on a loose bush, bored and turned to fit the two, with a small collar and set pin at the outer end for fastening on the shaft; this would be a much better job than any composition, and is a very general thing nowadays; cast iron and cast iron would then work together, which is to be desired.—Mutual Improvement.

[3774.]-LOOSE PULLEYS, fce.—When worn in, the hole should be bored out sufficiently large enough to allow substance for the bush, which may be good gun metal, and will wear very well ; the bush should be pressedin tight, that it may not move in the hole, and when it wears out, whieh will not be for a htng time, if properly oiled it can be knocked out, and a new bush put in without doing anything to the hole in the pulley.—Jonath.

[3776.]—BOILER SAFETY-VALVE.—"One in Need." has not given quite enough information to enable me to answer his question exactly. Does the weight of valve and lever, as Btated by him to be 7Jlb., give the true pressure exerted by them on the valve when in place? I expect not, and should imagine their effective pressure on the valve to be at least 211b. Since the area of a 3-inch valve is 7 square inches, this will give Sib. per square inch. So the weight will have to balance only 571b. per square inch, and will be found thus;—

7 sq. in. X 571b x SJin

■ = about 56lb.

20in. + 3ttn.

[3776.]—CASE FOR FERNS AND MOSS.—The best form is to make the legs and upright rods which hold the glass m one length, with a light rod running round the top, in the underside of which is a groove, There should also be a groove on the top edge of the box which holds the soil, and the glass made to shde on one aide to allow the planta to be got a t

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[3779.}— BOILKR.—" One in Need," should give the effective weight of his lerer, and the weight of the valve; if he is unacquainted with any method *f finding the ваше, he may get it as follows :—Place the lever at the fulcrum on a three

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sided file, and fix the short end, at the centre of motion, hang weight sufficient to balance the long end, thus the effective wtight is the weight required to balance, and the weight of lever, to which he must add weight of valve.—Jonath.

[377»-}—BOIXER SAFETY VALVES—According to "One in Need's '* figures, the weight required on end of lever would be 671b. lOoz., but 1 am afraid the 71b. Hoz. weight of lever and valve does not include the effective weight of lever, in which case he is altogether wrong.—Mutual ImproveMent.

[S779.J-BOILER— A weight of 681841b. placed on the end of the lever will give the required pressure. This weight is not exactly correct, but it is as correct as can be calculated from his description of the valve. If he requires the exact weight, he must give the weight of the valve and lever separately; if the lever be of the same breadth and thickness through nut, its effective pressure can easilyhe calculated, but if tapered he must disconnect it, and try what weight will balance it, makingthepointin a line with the centre of the valve, the fulcrum.—Thomas J. O'connoä. [37S0.J—AREA OF SAFETY-VALVES.—The area of the t valves for pressure is not at all affected by the difference of form shown in the two sketches. They are, however, not good forms of valve, as when the steam is blowing off strongly the current is considerably impeded by meeting the flat or concave surface of the valve before escaping. The form of valve ordinarily used on locomotive engines is, perhaps, the best of be simple valves, and is somewhat thus, the

Beating being a ven small mitre, or sometimes a narrow flat ring of bearing surface.—Q. Q. К

[3786.1-ÀREA OF SAFETY VALVES—I think "Flat and Concave Valves " will find on a little consideration that there is no difference between the two, because if there seems to be more surface in the concave, the column of steam is only 4in. dia. in the pipe's neek. Did he ever hear of the man who made a corrugated piston bottom, so as to work the steam on a greater area ?—Mutual Imhovshent.

[3793.]—COOKING BY GAS—If the gas is not under the meat inside the oven, the meat is quite as nice as that done before the fire. We find the best way is to put a Bunsen burner under an iron plate and cover this with a large tin cover, which is cased in flannel to prevent loss of heat. The meat must be supported on a stand in the centre of this, with the gravy tin under it. By this arrangement the meat is cooked as before the fire by hot air, and the most critical person cannot tell how it has been cooked. The same burners

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coal at 28s. per ton, for less than 2s. per week. At present we hare four cooking burners and cook for seven people never using the fire for any purpose, and I estimate the cost for cooking to be aboutis, per week ; this, of course, includes boiling water for children's baths, washing floors, &c—A Dentist.

[3793.]—COOKING BY GAS.—I beg to inform "J. M.D." that 1 cooked by gas for several years for a large school. The flavour of the meat, &c., were not only preserved, but the process was cleaner and cheaper than the usual mode. There should be a pipe on the top of the oven for the escape of the carbonic acid gas, &c, which should pass into a chimney or the open air,—-J. Dyer.

Í37W.]-POLISHINQ STEEL.—'* Cylinder " must be sure this clock is good metal, that his stuff is good, and that his steel was properly hardened before it was tempered, and not etnpercd too much. He must have everything clean, and not dust flying about The block must be refiled before each attempt, the least quantity of red stuff used, and the polishing moved very little during the process. Anything more is difficult to describe, as it is by the feel he will know when he has rubbed enough. It all depends on leaving off at the right moment—Nobody.

[3797.]—TELESCOPE STAND—If Mr. Turton will call at Brunswick House, Tanner's-hill, New-cross, he shall see the stand and mounting of my ihn. reflector.—J. Dyer,

[3798.]—TUBE FOR9iN. REFLECTOR.—The thickness of the sheet iron of which the tube of my telescope is made, is rather over the 20th of an inch- The tube is 7ft. 5in. long, and the focal length of the speculum is 6ft 6in.—J. Dïer.

[3799]-BRASS COIN.-Ie a Nürnberg counter. As many of those legends hare no meaning, and some of the devices fanciful, it is next to impossible to gire further information about them than what has been given. A friend of mine laughingly said to me the other day, " I think the Nürnbergs have been pretty well worked or used up in the English Mechanic." I quite agreed with him, and I am

Eretty sure, Mr. Editor, that when you sec one again you will eable to say in your" Answers to Correspondeuts " what it is without giving us a woodcut—D. T. Batty, 9, Fennellstreet, Manchester.

[3801.]—LEVER ESCAPEMENT.—"Gracchus" asks for plain instructions to plant a lever escapement. This implies that all the pieces arc readr made, and all he wnnts to know is how to plant or pitch them off into connection with one another. But as he adds, "proper dimensions," &c., he evidently wants to be shown how to make a suit of clothes to fit anybody, "proper dimensions," of course. I must remind him that a knowledge of the escapements is acquired studiously and with great application by all who wish to know anything of their business. The subject will hear no trifling with, and "Gracchus " must not think to get off less easily. I could do nothing to help him without an accurate plan of what he wants, or at least the half containing the escapement; and then if he knows nothing on the subject, all my explanations will be double Dutch to him.—Nobody.

[3803.]-CnANGING COLOUR OF PRIMROSES.-I have about half a dozen differing in colour from vellow to a very dark purple. This change was caused by being yearly transplanted into richer soil. They first come au orange colour, then a light red, and eventually purple. Tbe following recipe will show "J, D. M." how to change other flowers-.—The colours of flowers may be changed by certain additions to the soil in which they grow. Powdered charcoal deepens and intensifies. The flower of the dahlia, rose, petunia, &c. Carbonate of soda reddens hyacinths; and superphosphate of soda alters in various ways the hue and bloom of other plants.—W. F. Наши.

Г3810.]—CYLINDER PATTERN-.—Let amateur make his cylinder model similar to sketch, the main feature of which is

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the valve box and thoroughfare cores. In the first place, pnt a good core print on valve box, then make a core box to suit the print, and inside this and from bottom side screw on three pieces of wood exactly where the ports want to be, and let them come through the top, and by making the core box for ports long enough to come through the valve box core, it all goes in together and prevents the moulder haviug to put studs in to carry the cores of the port By putting a thick print on valve box it gets a good bearing surface for the cores. —john W. Bedford.

[Зв13.}—POROUS CASTINGS.—This short query would admit of a very long answer; but I will try and make it as plain as I can. 1st. The sand is a very important thing; it it contains too much clay it is a great difficulty to oiake castings free from airholes. Clayey sand la only fit for light castings, where good impressions are of value, likewise avoid everything that will generate gas, euch as coaldust, charcoal, and like substances. Rani your mould regular, and vent or

S ierce it with innumerable airholes; cast or pour it with as ot metal as you can get, not forgetting to run it in the mould as quick as it wiU go in. The suflage must be kept back with a skimmer during the pouring of the metal in the mould, and the head or git must be made so as it will be kept up or kept full during the casting operation.—N. L.

[3819.]—CHEAP GAS.—A great saving in the consumption of gas can be effected by regulating the pressure of gas on the burners. When more gas flows to the burners then they can properly conihust, the illuminating power of the gas is deteriorated, and, of course, the gas bill is increased. One of the best ways to prevent tbis waste of gas, is to hare a good regulator fixed near to the meter, whicii would regulate the flow of gas to all the burners. Another plan I have also adooted, that of placing a diec, with a Suihii hole in the centre for tbe gas to pass through, in the elbow or brass socket in which the burner is screwed. The whole in the disc must be made according to the sue of flame required at the burner. 1 have been able to save ¿5 to 30 per cent in the consumption of gas by udoptiog the aboro. With regard to

the carburisation of gas by causing it to pass through a vessel filled with some hydrocarbon, this plan has been tried under two or three patents for tbe last SO years, but nearly in alteases where it has been adopted, after a long trial it has been abandoned on account of the difficulties, and the absence of the economy anticipated. A word respecting gas regulators, and regulating burners:—Tbe best regulators for fixing near the meter that I know of (and I have tested several) are those made by W. Tices. 65, Bartholomew-close, E.C., and by W. Sugg, Vincent-street. Westminster; Sugç has also n good regulating burner. Nearly all the regulating burners offered to the public are worthless after they have been in use for a short time,—L. И.

rSSÎOJ-AQUATIC BOTANY.—Stratiodes Mtiedes. or Soldier plant There is no plant so beautiful and interesting as this for the above purpose. Tie it to a stone and sink to the bottom; it will soon seud up young plants on long stems reaching to the top of the water like so many juvcuile palm trees. After a time the stems decay and the young plant floats free, of a lovely transparent green. They will soon require thinning out; for this purpose a tank should be out of doors, in full sunshine, where those not wanted si be placed, when they will get strong and change toamahoj brown. Returned to the aquarium they will gradu through all the intermediate shades till they mra| green hue, A constant interchange of tint may thus be kept up. The plant may be grown of any size, according to thtt of the vessel, and increase abundantly.—Ajcatkoe

[3824.]—GOVERNORS.—I can recommend Porter's patent governors as being very sensitive and powerful. They revolve very quickly—usually from 300 to 400 revolutions per minute—and when properly proportioned will not allow a variation of more than perhaps 3 percent; so that a shaft running at 60 revolutions per minute would not vary more than 3 revolutions per minute. These governors arc ¡n±tlc by the Whitworth Company, in Manchester.—Q. Q. R.

[3827.]—NITRATE OF SILVER STAINS.—To remove the nitrate of silver stains, pour on solution of potassie iodide, then nitric acid twice diluted, and then wash with hyposulphite of soda. I have foand this succeed in removing stains from the hands, but care Im required.— Ohio.

[3829.]—SOLDERING.—Perhaps the tollowiog may be of use:—A lute for the joints of iron vessels may be composed of 60 parts of finely sifted iron filings and 2 of sat ammonite in fine powder, well mixed with 1 part of flowers of sulphur. This powder ii made into a paste with water, and immediately applied; in a few seconds it becomes hot swells, disengages ammonia and hydric sulphide, and soon sets as hard as the iron itself.—Ohio.

[»4.3—DUMB BELLS.-See "Physical Education." by A. Maclareu of the Gymnasium, Oxford. Clarendon Prosa Series, 6s.—Ohio.

[3836]-PITCH OF PROPELLER.—The first thing "T, J. O'C. ' must do is to bore out the eye of tbe propeller in the lathe, and fence np the outside end of the eye for too nut to bear properly that secures the propeller on u¡- shaft; then take it out and lay It down on the gTvund with that sideupthatis faced for the nut, and level it up all the four ways of that part that is faced; then puta centre into the eye of the propeller, and from the centre of the eye draw a circle with any radius ou that part of the eye that is faced for tbe nut, and divide that circle into 12 equal parta, and also divide the blade from the centre ot the eye to the point into feet, and draw tbe linee across the blade with a radius from the centre; then take a straight-edge that will reach from the point of the blade to over the centre, and lay the edge of the straight-edge on the point where one of the dirigions cuts the circumference of the circle and nukes it run into the centre, and keeps it in that position by laying a block of iron on it; then plume down from the edge of the straight-edge with a centre plummet to the divisions on the blade, and mark then with a centre punch; then measure the disttnee from the edge of the straight-edge to the plume point on the bladepresume that it is 6in.; then turn the straight-edge to the next divisions, still keep it running into the centre, and iikewise level, and plume down with the plummet again to the blade, and mark it, and then measure the distance down again from the edge of the straight-edge to the plume point— presume it is 20in. Now the difference between 20in. and Cia. is 14in. ; then as every inch of the perpendicular distance gives 1-12Ш of the pitch in feet, therefore 14in. would be a 14ft pitch to the blade of the propeller; and if the blade is not broad enough to take in a twelfth part, divide the circle into 2+ parts and the blade into 6in . and every im. in the perpendicular distance, in the same way, will give a twentyfourth part of the pitch, and so on. The most convenient way to divide the blade is to divide the straight-edge into feet or half-feet, as it is required, and square lines across the edge; then make one of the lines coincide with the centre of the propeller, and the edge with one of the points on the circle, and then plume down from these pointa to the blade and mark them ; then measure the distance- down.—G. B. D.

[3845.] _ BOEHM FLUTE.— In answer to "Another Flautist's" inquiries respecting the Boehm flute, I may state that the use of the rings is to stop holes which are beyond the reach of the fingers. On the old flute the holes are altered from their true position from the inability of the fingers to reach them; hence its notes are unequal in power, and are " out of tune." The latter defect is partially lessened by sltering the size of the holes, but at the expense of adding to the former. Boehm overcame these difficulties by placing the holes in their natural places, and by making them of equal proportions throughout (the holes being made gradually smaller and smaller through a regular progression upwards), by which means he obtaiucd uniformity of force and tune, and great increase of power in the whole scale of the instrument But these advantages were met by a great drawback, for he found it necessary to alter the fingering of many not«; and this involved to'those who already knew the old flute the unlearning of one system of Angering and the learning of a new. From this cause many, seeing the superiority of the Boehm flute, became dissatisfied with their old flutes -, but finding the difficulties of the new fingering too much for their patience, gave up flute-playing entirely. Some few years ago Mr. Clinton, the celebrated flautist, invented a flute called the "equisouant flute," which not only had all the advantages of the Boehm flute, but retained the old fingering, and with increased beauty and brillancy of tone to tbe instrument itself. The writer of this has had practical experience of all these flutes, and much prefers his "equisonant " to any other. Wbat 1 have said about ilutes will equally apply to В clarionets. It would take too mnch space to describe flute machinery thoroughly.— H. T. Lbftwich.

[If Mr. Leftwich desires to treat the subject more fully, space is at his disposal.—Ed. E. M.]

[38W.]—NICKEL.— The following extract may perhaps be «f interest to "Another Flautist'*:—" Nickel (Ni 2frâ7),*

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Uif ft greyish-while colour, wua rciinntnuic magnetic rtitt. wbxh it loses on being heated ta 660°- It is t tad malleable. A. Bavarian coin has been struck in octal, ami the impression of the die is snid to he very П. The sp. gr. of nickel varies from 8*27 te 8 40 when fand after being hammered, from 869 to 9*0, it has a /melting point, and is hat little acted on by dilute acid*, five nickel is found in the Erzgebirge in small quantities. jpfeniiekeJ, or copper nickel is an arseniuret, and is also tdersblv abnndant. The nickel of commerce is obtained '"'rtiiefly from kupfernickel, nickeliferous pyrites, and from the •piess obtained as a secondary product in the treatment of the nickeliferous ores of cobalt. As there has been a great demand for nickel in the manufacture of German silver, some improved methods of obtaining the metal have been introduced. They are, however, kept secret; but Mr. Phillips, in his Manual of Mineralogy suggests the following as the process likely to be followed:—" The roasted ore or spiess, after being dùaohed either in sulphnrie or hydrochloric acid, to which ejtber nitric ncid er nitrate of soda has been added to peroxidase the metals, is placed in large vessels, in which the insoluble matters are allowed to subside. The clear liquor, after it bas cooled, and the copper and lead which have been precipitated by sulphuretted hydrogen, may be decanted off and treated by carbonate of lime in the form of common chalk, by which the iron and traces of cobalt will be precipitated, whilst the greater portion of the cobalt and the whole of the nickel will remain in solution. After the oxide of iron thus preeipitoted has subsided, and the liquor has been again syphoned off, the cobalt may be thrown down by saturating the solution with chlorine gas, by the addition of hypochlorite of lime, and then adding carbonate of lime- The liquor syphoned from this solution contains the whole of the nickel, which may now be precipitated by ebullition with hydrate of lime, and dried and reduced in the usual manner -uauby G. Newtoh.

(3850.3—THERMOMETER.—" Thermo " had better place his thermometer against a piece of ice, which will have the effect of causing the mercury to recede towards the bulb; but if the bulb is not broken much, it will вооп settle of itself. —Skupkb. Pajutus.

£8851.]—HARNESS—* Equestrian " will find the best way to elean bis harneas is to well wash it in warm soap and water, (soapsuds would be better), dry it thoroughly, and then rub neat'sfoot oil on it; let it stand till next day, and if it absorbs the oil readily, give it another coat. This treatment is suitable for any kind of harness or leather; but if the bridle is a black one, 'he will find n great preservative in Harris's harness composition—Skmpkr Paratus.

[3852.J— BRASS INSTRUMENTS.—They fill the tubes with melted resin, and twist them about when cold with apparently as much ease as they would use in bendiog a piece or cord. No doubt a sharp loot out is kept for puckers, which they hammer in directly they appear on the inside of a bend of conree with a small round-faced hammer. Copper tubes may be filled with lead, but it is dangerous with brasj ones, as, to get the lead out, a (good heat must be used, which snakes brass brittle, and тегу likely to gire way with the weight of the lead. I saw Distin a factory once, and was quite struck with the tube bending, which I had supposed such a delicate operation. I believe it is very difficult to get bruises out of tubes, and that they have a sort of jointed metal mould to put inside a Ml which has a bent tube to it, and which has received any injury.—J. K. P.

[3852}-BRASS INSTRUMENTS.—The bends of brass instruments are made by first filling them with lead, and then bending them; after that the lead is melted out. The reason they require filling with lead is to keep them from bulging ont at the sides. The lead would, however, be inadmissible in the case of tine tabes, as they would melt wheu the lead was run out. I am told resin would do instead, but this I hare not tried, 1 should advise "Clutha" to try it, and report progress.—Skupkr Pabatcs.

[ЗДбО/J-COPPER COIN,—Is of Cathcrioe II, Empress of Russia; no value.—Bkrnakdin.

[3663-3—PASTILLES.—Take 8drm. of cascarilla bark, 4drm. of gum benzoin, 2drm. of styrax, 2drm. of olibanum, 601. of charcoal, l|drm. of nitric, and a sufficient quantity of mucilage of tragacanth. Powder the substances and form into a thick paste with the mucilage, and divide into small cones; dry them until quite hard in a slow oven.—Minnehaha.

(38d3}-pastilles.-"w. R, C." asks for some recipes for fumigating pastilles; I send the following, copied from a book which 1 believe can be relied on, but not proven on account of the difficulty of obtaining one or more of the components:—Pastilcs á la rose Essence of roses 1 part, nitre 9 parts, gum 12, tears of otiuanam 12, tears of atora* 12, powder of roses 16, charcal 64); powder the solids very fine, and make a paste with giro tragacanth, 2 parts dissolved in rosewater3S— Pastilles à In-Vanille: Gum galbanum 25 parts, tears of olibanum 2ó, tears of storax 'Jó, nitre 2b, cloves 25, vanilla 35, charcoal 115—make paste as above—Orange Flower Pastilles: Neroli 1 part, nitre 9, galibauura 13, tears of olibanum 12, tears of storax 11, pare orange powder 12, charcoal 70, reduce to fine powder, snd make paste with gum tragacaath 2, dissolved in orange-flower water 15, and rose water 17 parts.- Lastly, but hardly fit for a sick room, Etplofiive Pastilles: Make a hole at base of pastille and fill with gunpowder. I am afraid the queer names of these fragrant resins will almost frighten the querist; but 1 believe all except tears of storax and neroli can be bought in pennyworths at the druggist's-, if one shop does not keep them, try another. They say that tears ot storax have not been in the English market for vears, but 1 believe the liquid storax wül answer the purpose. By the word "tears *' is meant the drops of resin in that simpe, but of course the lumps will do as well. Orange and rose powder I take to гцечп powdered orange and rose flowers. Neroli is the essenti4l oil of orange flowers. I will now give a simpler way lor fumigating, but which has this objection, that everybody does not like the perfume. Dip brown paper till quite soaked in я sti*>Dg solution of nitre; then, when perfectly dry, rub over it n Tarnish made by dissolving either or both gum olibanum {franktncease), and gum benzoin this soon dries und is reudy for use; this last I have done myself, and succeeded in getting u strong fumigan*, -H W. Bishop.

13071..] -THROTTLE VALVE—1 Bend for "Grocer's" benefit a full size drawing above of one 1 put to an engine of *t' cylinder. The same ihing reduced to J gns barrel which measures aay ¡ inside and the casting bored to I" would do tor a 1 h.p. engine. The lower section uf pipe is screwed and brazed into wrought irou Jiangs and faced oif in the lathe bring & short length jiltogetUer, the upper flange casi iron sp|»ed for barrel, which is screwed, in with white lead. The intermediate piece, и like u pulley with large hole through, aod*cry dc-i'pgro ,#v with ■» piece el иск ш the pattern atuue

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side to be bored out to make stuffing box, and a small boss opposite side to pre veut spindle hole coming through, all bolted together with 3 bolts. These are prevented from turning by three flats filed on edge of moulding on casting as shown on plan, Fig. 3. The valve is cast with two tails for centering in the lathe, and a finishing cut taken with the slide rest to exact diameter of valve case. See Fig. 4. To get it out in case of wanting repair, slack nuts 4 turn, and let a little steam on, theu take out bolts, und all comes asunder. You need not cut off the tails from valve if they are not long enough to gain when valve is full open, which it would be by moving 3ü°—J. K. P.

[3866 J—LATHE AND ITS USES—For the information of G. Flackburn, the universal cutter epindle of which he sneaks works or rotates m two internal hardened steel cones, the two ends uf the spindle being external. The square bar which fits into the receptacle ofslido rest of a б-in. centre lathe Holtzapffels standard is 9 l-6th square and 4J long. Perhaps I might add that I have arranged and now make a far superior instrument for simplicity, effectiveness, and durability than the one represented in Vol. V., p. 202, Fig. 256, and do hope before long to give the English Mechanic a representation and description of it.—Edwin Baker.

[3867J-LATHE DIVIDING PLATE—If " R." requires a ready reckoner to as&iat in working the above, I shall be happy to make him a present of one for that purpose, if he will let me know his address.—Edwin Bakes, 13 and 14-, Mount-street, Grosvenor-square, W.

[38871-LATiIE DIVIDING PLATE—If you look at p. 12 of present volume, you will see a counting index figured and described in connection with the wheel cutting engine. It is not very troublesome to fit up, and need not be self acting,—J. K, P.

[S868.1-WATERPROOKING CLOTH—Make a solution ofindui rubber ш naphth.i, and apply it to the cloth; this is the article used for waterproof coats; add a little linseed oil to it. If this is not suitable to '* A. S. A." I can send a few other recipes.—Srmfkr Paratus.

[3869]-WEIGUr OF WATER. -The reply to " Countryman's" query is very simple. By a rule in hydrostatics, any body immersed in water is pressed by the weight of ¡i column of water the height of a perpendicular drawn from the centre of gravity of the body to the eurface of the liquid, and in breadth equal to the cross section of the body. A rnle to calculate the pressure on the bucket may be stated thus: for every 7ft. of depth allow 31b. pressure per square inch.— A Bodohey.

[3869.]—WEIGHT OF WATER—It is said that any heavy body 201o. iu weight, taken to the top of a mountain 8 miles high, loses but $ог. in weight ; therefore the difference in weight of a bucket of water ut the top and bottom of a well 90ft. deep, must be indeed slight. The apparent difference is, I thiuk, due to the weight of the rope when the bucket is at the bottom.—Harry G. Newton.

[337Я.}— BOOKBINDERS' GLUE—Bookbinders use the same glue as curpeuters und joiners, but breuk up the cikes into small pieces, and souk them in water for 8 or 10 hours, then thoroughly melt them in an iron or earthenware pot before using in the glue p)t ; some add treacle when using it for cloth work; euinr. iidd paste. There is a M'ork called "Bibliope^ia," I thiuk it is by Ar not t. I do not kuow the publisher, but if " Aristotle " will insert his queries in " our" Mechanic, they will receive prompt attention from—An Initio.

[:W74.] — CONSTELLATION—The group "Aristotle" sketched is the Pleiudcs, as he will ut once perceive ou a

closer look at the group on page f>3 of " F.R.A.S.V maps. He wauts a sketch of the Pleiades; I refer him to his own on page 238 of present vol.—H. W. Bishop.

[3876.J-TOOL FOR TURNING PIVOTS.—The latest tool for turning pivots is the French turnbeuch, with 3 centres and a small slide rest. They are from 10s. 6U each and upwards.—S. Tanknbxrq, Leeds.

[3878.]—DAILY TEN O'CLOCK TIME SIGNAL—Yes; all wires from Imin. to 10 o'clock to lmin. after 10 are in connection with Greenwich clock, when all working is suspended forthat time.—A Teleorapu Clerk.

[3879.]—GINGER BEER, —White sugar lolb., lemon juice 9o£., honey lib., bruised ginger lloz., water 9gaL Boil the ginger in Hgal. of water for half an hour, then add the sugar, juice, and honey, with the remainder of the wuter, and strain through a cloth. When cold add the white of one egg and ioz. of essence of lemon; after standing 4 days bottle. —(Extracted.)—Minnkh Aha.

[3897.]— NAPOLEON,—I beg to inform "H. В.", p. 231, that his coin of the French Republic, 1848, is not worth much more than its weight in gold. If it is, as I suppose, a 20 franc piece, its intrinsic value is 15s. lOid. in our moner — Henry W. Henfrey, M.N.S., be., Stc.

[3900.] —ASPHALTE FOR ROOFING, &c. —I would advise " Dublin Printer " to try the following; he will find it useful in stopping many a crack besides those in his roof :— Take 2 parts by weight of common pitch with 1 part of gutta percha, melt together in an iron pot; it forms a uoraeg eueous fluid much more manageable than gutta percha alone. Now to repair his gutters, carefully clean out of the cracks all earthy matters, slightly warm the edges with a plumber's soldering iron, then pour the cement in a fluid state upon the cracks while hot, finishing np by going over the cement with a moderutely hot iron, so as to make a good connection and a aoiooMi joint. The above will repair zinc, lead, or iron gutters, and is a good cement for aquariums.—Patience

AND PE RS EVE RAN CK.

[.Ï907J-UNIVERSITY EXAMINATIONS—London, 1871. Special subjects;—Ist B.A., Latin, Tacitue, "Annals," Book I.; Virgil, '.Kneid," Books VII. and VU I. English, History of English Literature during 17th Century; Bacon, "Essavs ;" Shakespeare, "Julius Ciesar; '* Dryden, " Annua M irabilia ; " and " Absalon and Achitophel ; " French, English, prst and preaeLt. If "Xanthos" will write to me, 1 will give him any information he may require upon this subject. С H. W. В.

[3908.J-OLD COPPER COIN—In answer to Mr. Nash, p. ¿39, tue inscription on his coin is FAVST1NA AVGVSTA (Faustina Empress). I cannot say without seeing the coin whether it wua struck hy the elder Faustina, wife of Autoninun Pius, horn A D. 105, died A.d. 111. or by the younger Faustina, wife of Marcus Aurelius, died A.d. 17¿. The bron/e с uns ni both are common, and worth very little.—Henry W. Hkverey, M.N.S.. &c.

CHINESE VACCINATION—It may be new* to some that the Chinese commenced to practise vaccination for the Mii!ill-¡) >x at Canton forty years ago. There are naff public vaccinators at f'ekin with regular day« and hours lor scarifying iufants brought to them, just As In London. Wheu their supply of vaccine lymph falls short, ir is renewed from the RngUsh missionary h ispítul. ..^^.t

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»OTES AND QUERIES.

[3910.}-CONICAL WINDING DRUMS. - Will some brother reader kindly gire «orne partirai»!« respecting the construction and working of conical or »piral drams, a» applied at collieries for drawing coals, and »tat« what conditions are to be obier?ed in order to ensure the» safe working 7—W. M., Junr.

[39U.]-GALVANIC CELL.—I have a galvanic сеП, composed of a stick of what I suppose to be carbon (it is black, about 5in. long, and lin. square) in a porous cvlinder »urrounded by a line cylinder about Sin. in diameter, all in a lasa vessel. Will any of your readers kindly inform me what „quid or solution I should uae to excite it ; also the name of the combination, and whether it is best adapted for streng! h or constancy r—Hsuur.

R912]-REVOLVING FRAME FOR SHOP WINDOWS. —I wish to construct a revolving frame to show picture» in a shop window, and find the ordinary meat-jack clumsy; it revolves too rapidly at times, and require» winding up during the day; I should like also to avoid the return motion. Can any of your correspondents help me?—Pitman.

[3913 ]—TO A. STRINGER—In No. 2(19 A Stringer writes 6n velocipede construction ; will he kindly, for niy own and the information of others, insert a plan with the details of the three-wheeler he speaks of steered like a boat -, will he also say where I can purchase an "English" velocipede?—ConStant Subsckiber

Г391*.1—WOOD ENGRAVING. — I shonM feel greatly obliged if any brother subscriber can tell nie where to obtain the best book of instruction in the above art, and the price? —K. T. Z.

[.4916.]—NAIL BAGS.—I have a large quantity of nail bags which are worn out, for what purpose will they serve; will they do for making paper, or must I consign them to the rubbish "heap?—W. Cat-tell.

[3916]-PAINTING BOILER—How can I mil a good green paint to paint the boiler of an engine so as the heat may not effect it ?—A. W.

[S917.J—ICE CHEST. — ICES.—Perhaps some of my fellow subscribers will tell me the best plan for making au ice chest (a few sketches would be a great assistance); also a few instructions for making icesf—Brighton Sub.

[3918—ENAMEL.—Can any of my numerous brother readers inform me how to make white English glass, or the tin enamel, as made in France, that given a few weeks back was not white or good: also where I could obtain a brush for painting figures and letters on clock and timpiece dials ?— Anxious Inquirer.

[39190-GALVANIC BAND-TO "SUFFOLK AMATEUR."-1 have very carefully made a galvanic band after the plan of " Suffolk Amateur," p. 11, last vol.,I have tested it with a small galvanometer, hut cannot get the slightest current from it I have made it as follows :—A strip of copper and one of zinc, 16in. long, lin. broad, and l-32th in. thick, arc united at the ends by small copper rivets, I have lapped over theso riveta with thread, and varnished over the thread with shellac in alchohol, the ends are left hare ljin., the copper and sine are lapped* spirally round with a piece of cotton list lin. broad, and covered in a bag of oil akin; I tried all strengths of vinegar, but to no purpose. Would "Suffolk Amateur" kindly aay where I have failed?—W. A.

[39S i.j— MEASURING LIVE STOCK,—Will some of your learned correspondents inform me if theiris a bookjpublished on mcaauriug live stock, aay an ox ; or give a rule, through the medium of our Mechanic, to measure a living fourlooted animal so a» to find its weight?—A Countryman.

[3921.]—BRASS COIN.—I have a brass coin the aiie of a penny, on the obverse the bust of a man, on the revene a female in chariot drawn by four elephant» with LIE over them, there is an inscription round the bust, but the only letters I can make out are ALT—PAIANC I should like to know of what coin it is, and of what value ?—Том С. HolloWay.

[3929.}—REMOVING PAINT—Although aome answer» h ave appeared in reply to inquiries for a good alkali or each method for removing paint, still not one effectual mode has been suggested. If any brother reader could advice a ready and effectual method of softening the old paint on dorrs, fee, when it becomes thick and hard, so as to remove it speedily (without the use of charcoal fire), and enable the operator to clean off mouldings with credit, it would he a very useful enlightenment?—Носах Paintïb.

[3923] — GEOMETRICAL DRAWING. — A method of drawing the ellipses that represent circles—N.B.—When the dimensions are not reduced to geometrical proportion ¡ if one can also recommend a good cheap work on the above ?—Cael J. H.cottbesson.

[39J4 J—SILENT FANS,—Can any of our readers tell me the diameter of the blade of one of Messrs С Schiele and Co's SOin. Excelsior silent fan», patented 1863 ?—One Who Wants To Know.

[3925.] —POSITION OF MAGNETIC POLE — Can any of our tenders inform me whether, as the declination of a needle is the angle made by the magnetic and Seographical meridian» of any place, and the magnetic mtriian passes through the magnetic poles, when the declination alters does the position of the magnet pole change with it ?—

VIBRATOR.

[39263—FORCING WATER.—An engine forces water through a 9in. pipe, perpendicular, to a height of 30ft, will it require the same power to force it to the same height through a !Mn. pipe, but auch height being 180ft. away, with a gradual ascent of 1ft in 6ft. ?—B. S. M. G. H.

[3957.}—WINDOW PAINTING—I shall be very grateful to any of your readera who will tell me of a rich transparent

Ïiermanent crimson; also a pure bright yellow? Crimson ake is such a varnishing colour it will not hear continued exposure to daylight, the colours are to be used with oil and varnish for glass painting. Amongst all the varied and valuable information contained in your journal, I have never noticed any on the old act of window painting, 1 do not mean the modern process of staining, I have been a painter of dissolving views for year», but I should be moat thankful if you ojuId assist me m the former matter—Sable.

[ЗУ28 ]—RE-MANUFACTURING INDIA RUBBER,—Will some reader kindly tell me if india rubber of first-class quality, in sheets of Jin. thick and under, could be re-manulactnred, and what it would be worth per pound?^J. T.

i*ei"9."— EMIGRATION.—I should be pleased to get all the information I could respecting New Zealand and Tasma

nia, as plAces suitable to make a home in, particularly as to
peculiarities of climate, soil, productions, reptiles, insects,
fcc if any insects to give much annoyance like the mosqui-
toes or gallinippers of the Southern States, U.S., which
1 have suffered considerably from, I reckon. I do not wish to
g о where it is very hot, but »little milder winter than our
own with it» cold dull weather and piercing easterly winds.
Perhaps our kind friend "F.R.G.S." would oblige—Tas-
Mania.

[3930.]-rWINES, JAMS, PICKLES AND PRESERVES —
Can any of your readera inform me if there is any practical
work on making wines, and also a book on manufacturing
jams and pickles. I have one, but it is of little use for a new
beginner.—Francs» Brown.

[3931.1—INDIA RUBBER SOLUTION. — Will any of your obliging correspondents, "Sigma,"for instance, tell me of what the india rubber solution for mending waterproof clothing is composed, and the proportions of each material. Also whether there is any »olvent for »ilk, which on evaporation leaves the thread without decomposition?—Alecia Brown Inq.

[3932.]—BICYCLE RUBBER TIERS—I intend fitting an india rubber tier to the driving wheel of my bicycle, conld any brother subscriber kindly assist me in the fixing? Ido not want to remove the iron tier; should also like a practical opinion of the merits of the rubber tiers, best shape, depth, fee.?—C. Mortimer.

[3933.1-HYPOPHOSPHITE OF IRON AND QUININE.WiU any brother reader kindly inform me of the medicinal properties, doses, and cost of the above preparation of iron and quinine?—May.

[3934.]-ORGAN ACCORDION STAND.—Will any fellow subscriber furnish me with a diagram for the construction of the above, so that it may be played with both hands—the feet, by means of a pedal, giving necessary action to the bellows ?—Siomatau.

[3986.]—DISSOLVING SHEEP'S HORNS.—Could any of your numerous readera inform me how, or in what way, I could dissolve sheep'» horns to make them into glue, sue, &c , or for any manufacturing purposes ?—Very Old SubScriber.

[SS30.]—FAST COLOUR FOR SHEEPSKINS.-Will one of your reader» kindly inform me how to dye the wool of sheepskins (fast colour) without injury to the pelts?— W. С S.

[3937.] — CHEMICAL QUERY. — ÎOOgrm« of liquid nitrous oxide are gradually warmed to a temperature of 0°C.,tlie barometer standing at 760mm. What volume will the gas occupy? Will E. G. Davis, " Urban," or aome other friend kindly answer the above, and also »how the way in which the answer is got?—Zeta.

[3938 ]—AMERICAN CLOTH BAG.—Having to use in the course of my business a large light tight bag, made of American cloth (being light and cheap) I find it answer when the weather is warm, but when cold the enamel chips or peels off, and is soon useless, will any reader tell me how I can prevent this?—Pbterboro.

[3939.]—ELECTROTÏPING,—Will any one please inform me how to take electrotype impressions in brass or in any other inexpensive metal harder than copper ?—Herbert.

[3940.1-THREE-WHEELED VELOCE.—I am making a ... ... .

three-wheeled velo« for two to ride, and to drive off the of tee,h should the back gear whaels and pinionbe ,■

[ЯМ6.]—SYRUP OF HYPOPHOSPHITE — Ifauy medical correspondent will inform me of the medical uses and coat of syrup of hypophosphit« of iron and quinina, together with the doae for ailments in which it is beneficial, 1 »hall feel greatly obliged?—G. Твлсж.

[39*7.]—REMKLTING UARD WHITE PAINT.— How shall I remolí bard white paint, shelled oft, composed probably of white lead boiled oil. and litharge.—

[3948.]—INDIA-RUBBER TYRES.—If some correspondent, who has had experience with india-rubber tires, on velocipede wheels, would answer a few questions respecting- them, they would oblige a nuruber of readers who are interested In velocipedes Where they can be obtained, and price? The beat way of fastening them on, and should they be used with iron tires? How long they last? How are they astened on the " Phantom ' wheels ?—G. K.

[3949.]—GUYANA.—Where is sitnstod the Republic of Guyana? A few particulars will oblige.—Jobs D,

[39.W.]—GOMUTUB FIBRE.—1 find in a Dublin paper that the bristles imported for the purpose of making brooms for sweeping the'streets, come from the Arenga or G4mutr> palm. Is this not an error?—GoMUTO.

[39äl.]-BAMB<JO NUTS.— I wish to know what kind of nuts are the " Bamboo nuts," I find mentioned in the circular of Messrs. Mandy, Horley and Co., last number of our Mecuanic, and what is the use of those nuts ?—Georgia

[3952.]—LOAM PANS—Having some of these to atactoccasionally, and much annoyed with them veining ¡aside, I shall feel obliged if any of our brother readera. having practical experience in moulding the same, will inform me the cause and remedy —inquirer.

[3953.]—COIL—As I am afraid I have annoyed Mr. A. E. Tucker more than 1 ought, perhaps " Sigma" would kiadly answer me one or two queries. I quite forgot to state formerly that I intended making my coil in four sections. What wnitd be the best way to connect them at the discs. I can almost fancy from " Sigma's" note inltbe lastnumber|of the Mxcu Asic that' there is a possibility of doing without so much gutta percha paper, as 1 see recommended by evervons. I only hope he raav show me how to begin, I'll be a willing pupil. Ihaie taken ' Mr. Tucker's advice, and intend putting 61b. No. 36 wire instead of 41b ; will " Sigma" also say if I should gst the new double mercury break instead of Mr. Ladd's spring break. 1 may state here that my old coil had a care i instead of jiu., as put in mv note. (This is in reference to Mr. E. Tucker's reply to my last query, which I have to thank him for.)—D. Forbes.

[3954] - SCREW AND WHEEL CUTTING LATHE.—Would "J. K. P." or any of your numerous correspondents kindly give me their opinion on the following :— I am going to have a 4iin. back-geared »elf-acting »crew and wheel-cutting lathe made expreaaTr for me, and I want it to be aa near to perfection aa possible without being too complicated. 1. Would a 8ft ein. bedaiu. across be the sixe i please give all the other dimensions) ? I should like it that length. 2. What »lie and rate should the ecrew be which goes inside the bed? it,««/ be inside. 8. What six« should the mandrel be, and what length ; is a i thread the right sixe to be as strong as necessary? 4. What sise and numuer

front wheel as in bicycles, and of hind axle with levers. I
am ata loss to know how to make the hind wheels loose on
the axle in turning a corner, as I am afraid if both fast on
one axle it would be very bad to turn. Will any reader give
an opinion on the following method, or suggest a better oue?
a if the back end of the nave, b is the axle, a section of, с is

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a projection on that axle, d is a projection on the end of the
nave, so that the projection on the axle will drive the wheel
by it on going round a corner. I think d on the ou'side
wheel would leave с on the axle going at the speed of the in-
side wheel. It is on the principle of a lathe driver.—
T T M

[S941.Í-MARKING INK.—Can any one tell me how best
to use printers' type and press with marking ink, for marking
linen, clothes, be. My difficulty is how to get the marking
ink on the type neither too much nor too little.—Daisy.

[3942.]—MAKING BUTTER—Will "Scorpio," or some other reader be good enougli to explain more fully the method on p. S13. Docs it not involve the digging of a pit, then , filling and then re-digging? Has any condition of ground to be attended to. What materials are the sacks made of ?— Omio.

[3913.]—BEES.- -I have a hive of comb in which a swarm | died last winter. Can any of your readers tell me is 1 may safely hive a coming swarm into it this summer, 1 may mention the hive is a common straw one with a wooden box under it quite full of comb, and is 3 years old. I feel doubtful in consequence of the comb being apparently dirty; it appears on the outside quite black, though I see no appearance of mould. Would it do to remove any of the comb to make room for the new swarm, as it is quito full. Some hints on the general management of bees by a practical bee keeper might prove interesting to many of your readers, as they would to me.—S. W.

[3944.]-ARITHMETICAL QUESTION.—Will Mr. J. Sharp, who answered query No. S710, p. 213, kindly show how it can be proved that a circle is equal to a parallelogram whose length is equal t« half the circumference, and breadth eqnal to half the diameter. If he cuu prove it by geometry, will he kindly do so ?-T. J. О. C.

[3946.]—PAINT KOR BOATS.—Would any reader inform

The slide rest must .have self-acting surfacing motion, what length should the bottom slide be, what length the top one, and what is the best form of tool holder for the slide real r 6. What is the beat wheel-cutting apparatus to fit in theahde reit to cut wheels up to SJin. in diameter F The moat spproved plan I believe, for dividing the head is a tangent wheel fixed to the mandrel, and the screw which turns it to have a band and dial; or is the rows of holes the best after all.—F. >. Hasluck.

[3955.]—SCALE PARAFFIN.—Can any of your readers inform me how many tons of scale paraffin are produced m Scotland in one year?—S. P.

[3956.] -CHEMICAL.—Will Mr. G. E. Davis be so kind as toshow how I could calculate the weight in gramme» of 1 hue of methvl gas at S0°C. and 760mm. preasure; and alio how to prepare acetic acid from the following : C,li,l. ttjU, CaO, II,SU4, K,Cr04, NajCOa?-R. Tbrsri.

[8957.]—POWERS OF NUMBERS.—Will Mr. Biggs, or some other contributor to our valuable paper, be kind enoorl' to inform me how numbers are raised to their 3'6th aua to their 17th power». Take No. 10 for instance, to theMili power = 8983. how is it done?—Economy.

[3958.]—NAMES OF PARTS OF BELLOWS.—Would any maker оГ Reverte's bellows and hearths, be kind enouib to give me the names, separately, of all part» of bellow», sud as is used in a ship building yard ?—E. Fowlxr

[S»59.]-THE "EDINBURGH" VELOCIPEDK^-Wul any brother aubsenber give the address of the maker of tsr "Edinburgh" velocipede ?—С. T.

[3960.]—THE BLOOD.—I beg to ask throughyoor valuable journal, if some kind reader would give nu a recipe (cheap) for purifying the blood?—J. G. Jackson.

[WeiO-BISULPHIDE OF CARBON PRISM.-WiU any hrother reader atate what cement will resist the a«u* ot bisulphide of carbon? I have made a prism, but the bisulphide dissolves all the cement» I have tried f—E. С Morrat. [8962]—WHITE LEAD.—I bought some stuff for " white lead genuine," but find it has all dried up. like old putty, although at first it looked like ordinary white lead, »»d has been kept covered up in water ; how is this ?—H.

[3963]-OAK, WALNUT, AND MAHOGANY STAINS. — Would some reader supply me with recipes for making oak, walnut, and mahogany stains?—Zembla.

Г3964.]-СА8Г IRON FOR TURNING.-I »hoald be much obliged to "J. K. P." If he would give me а few hints about preparing cast Iron for turning and filing, whether by chipping or pickling it. If 'he former, I should like to know the shape oí chisel, and mode of using. If pickling be the better way, I wish to know the »trength of acid, and time of duration of using It. I should also be much obliged by advice as to rctoronsinif a medal. It is one of a ease ot Napoleón medals, and the colour has been taken ofT by my attempting a oast In wax for eleolrotyptog, leaving It a dull leaden colour. I should like to know ho w to g«t a cast from it for eleetrotyping, as wax stick» to the metal and breaks. Plaster of Parle makes a pretty

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