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irrw or'their roots might be employed us filtercrs wound wclla suspected of impurity by the percolation of foul matters into the water within them.

I can Inform our friend "Bernardin," that ft few months ago I saw In a scientific and 3pticiMu'b shop nearly opposite Effingham. Wilson's, Royal Exchange, London, some recent photos of Australian scenery, including an "Eucalyptus/' *' Over Sixty '* had better invest in a " Macclesfield" tricycle, which is much cheaper aud mora easily worked by an elderly man than the "Edinburgh," -which, occupies a great space, and is actuated by the leg* aolaly. The steering, which cannot be clearly •oca flora a photo cr drawing, is managed by two broad, erossed straps attached to the from axles and the short levers on either eUie of the graceful vehicle.

1 congratulate you on the varied improvements in our

journal.

1*. France, Harrington-street, Liverpool

3IU. BEARDSLEY'S DYNAMICS.

Sir,—It appears that Mr. Vroctor and myself are at iv^ueon a particular subject—namely, upon one brunch of dynamics (or of the laws and properties of matter in motion), and he declares me to be "ignorant of the fundamental laws of dynamics." Cannot Mr. Proctor afford to be rather charitable than hostile? Cuunot be find more pleasure in convincing me 1 am in error, than in lighting me in the dark at (according to his own ahowiug) a rtlsadvantnge? Thousands of your readers cau ,-ubstautiat© my assertion on page 90, but it roust be borne in mind we must not tie ourselves hand and foot, as it were, to the so-called law?, brought into existence from necessity at the time other theories were advanced, and which I shall at a future time require to notice. I will not waste your valuable space further than to say I have done as Mr. Prjctor beseeches me not to do. hundreds of times, and find that the moment the feet touch the ground it is necessary to put the body in a alaotiug attitude to resist as far as possible the principle I named, arising from the forward motion of the train, and even after this precaution had been taken, found It necessary to put the feet into very nimble action. I must, therefore, '• beseech " lilm in turn, rather than adopt an uncharitable course Ju condemning me as ignorant, to prove me to he so, and I will at once '-lower my sword, and tender him my thanks. I shall albo thank him to point out when, where, and by what arguments Galileo laughed away what he is pleased to call my "puerile" objections about the earths atmosphere.

Joiin Beardbley.

THE "PHANTOM w WnEEL.

Sir,—Having examined Mr. Tydeman's letter at p. 385 of Vol III, in which, according to his further letter which appeared in the Mechanic, a fortnight since, he describes a wheel "of a precisely similar kind" to that made and advertised by this company. I now beg to offer that gentleman a simple denial of the Identity ; und, I think I may add, of the similarity of the two manufactures. The only point in respect to which the two wheels may be spoken of in the same connection is that both are "suspended" wheels. There ,i« so novelty, however, as to the suspension, and we have never claimed any. That is a'comparativeJy old alTair; Theodore Jones's patent "for it was issued In 1S20.

Your correspondent is emphatic upon the 'point that the failures and defects of the " Spider " wheel are inseparable from, and arc part of the suspension principle; and, whether Intentionally' or no, he leaves the impression on the minds of some, at least, of your readers—the two wheels being already rather dogmatically declared to be of a "precisely similar kind"—that the "Phantom" wheel must be certainly as useless as the Spider turned out to be.

The object sought to be attained in a suspended wh'd is to make it sustain a weight in motion In such n way as to lessen the degree of traction required ;on ordinary roads. This Is effected by hanging the axle in the centre of what 1 will call a continuous arch, or a circular spring, which, altering its arc, aud the portions of its abutments to a degree nicely adjusted to the weight of the load, the velocity of the mollon, aud the nature of the road, keeps the axle or load a» nearly ;is may be at a level with the lino of the road. To effect this, the material of the arch or circular spring roust be of an elastic, and yet very strong, nature*; something capable of receiving, distributing, and absorbing rather than of resisting concussion. The arch mast be made so as to bend iu as a whole, aud yet be unyielding in its parts. Its dimensions and substance should be well adapted to its work, and the principle of its construction should be such as to ensure the strain being distributed as evenly as possible over its whole area or circumference. A suspended wheel might be formed of a mere hoop of bamboo or cane, with lour strings attached to it at equal distances, and joined to a stock in the centre. Such a wheel, however, would not do for serious work, because it would fail to comply with any one of the conditions! have just mentioned. The bamboo or cane would not stand continued, concussion, and the weight oi the load could not be fairly distributed over the whole of the circumference from so few points of suspension; the stralu would be unequal, and would tend to pull the hoop Into a square »Uape by beading it outwards at the points midway between the attachments of the striugs to the rim. If, instead of only four there were eight suspending strings, the strain would bo better distributed, as it would tend to sake the circle into an octagon, and No on occoiding to the number of points from which the rim would be held In towards the centre of the wheel. The hoop could of course be made superior to anv strain whatever, even with only lour suspending strings; and, on the other hand, it might be made so light and springy, as to require to be held in at every inch «f its circumference by suspending rods. In either case the wheel would uot be elastic, aud nothing would be gained by the suspension principle so applied. The happy mean required is the adaptation of the material and the proportioning of the diameter and strength or the rim, aud the u umber and strength of the suspending rods to the work icquired of the wheel, Ho i hat each part of the atructuro shall have its fair share

of the load assigned to It, aud no more. The wheel, a* a whole, must be elastic enough to girt to inequalities of the surface of the road, and yet strong enough to recover and retain a perfectly circular shape where the road is good nod smooth.

It seems to me that Mr. Tydeman began badly by making his rim or arch In bad proportions, aud that he then failed to properly retain or keep It In shape by a sufficient number of suspending rods. A 1 in. stee. tuhf formed a circle Oft. in diameter, held in by wire1 rods niw. apart trom.eoch other on the ilui; thus what I will call tnescgmentsof his arch, the spaces between his suspending rods, were not far from tlat at starting. The tubular shape of the rim did not improve us elasticity, and whatever it had of that quality, must havo been soon destroyed by the "'aminer, 'aminer, 'nmraer, on the 'ard 'ighroad" which the cabman in Puueh\ speaks of. The rim was too weak and slender as compared wjth itsdmmeter,aud it7had far too little, or at any rate too widely separated,,helu from the very few suspending rods.

In a Phantom " wheel, of half the diameter of Mr. Tydeman's, we use a coutinuousrim of American elm,

3 lln. square. Iron eyes with stems, —in. thick pass

16 through this rim, and are fastened on the outside of It and tnmugh these eyes, which are only about 61 n apart, sixteen pairs of suspending rods are passed to be held in the stock in the way your readers may see by referring to our woodcut. The rim U, under any circumstance, such as that of being over-weighed, prevented from altering its shape to an injurious extent.

Mr. Tydemnn nays that the suspending wires of the "Sp'dcr " broke too icadily on being struck laterally.

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They wore only —in. black steel, in 10 The suspending rods of the 3 ■' Phantom " are in pairs,.each — thick, and only Ifllu.

16 long,; they are made, too, of a mild .tempered steel, prepared purposely for the job.

Further, the passing of tho steel rods through the steel rim of the "Spider," weakened it, and led to flattening at those points. This cau hardly be the true cause of tho flattening, I faucy. If the rim flattened in at'the rods it must have bent outwards where there were no rods; it would therefore, apparently, have been stronger at the rods. The flattening, however, was in all probability due to tho causes 1 have already referred to, and I can only emphatically deny that It Ib at all the case with our whecL

J. A.^iays, Secretary and Manager, the "Phantom" Veloce and Carriage Wheel Company, Limited, 10, King-street, Tower-hill, London, E.G., 21st April, 1*70.

THE KAKTHS FORM.

Sir,—It is no tempting task to take up and reply to the wretched stuff which Mr. Beardsley is inflicting; on your readers. In common with "Parallax." Mr. Hampden, aud all the others of his tribe, he sets forth as facts things which have no existence as facts ; he of course puts into the mouths of the orthodox, opinions which they do not hold, aud, as a uecossary consequence, his deductions from the one, and his ridicule of tho other, are both erroneous aud delusive. The " arguments " we have been favoured with, being within the compass of any half-trained schoolboy, win probably And plenty to answer them. My purpose Is to give onoor two on the other side—to set forth a real fact or two, which must first find an explanation before the globular form of the earth can even be doubted. J? irst, if the earth be uot round, how is It we manage to go round the earth; that is to say, if the earth Do one continuous plane, by what conceivable process is it that by going steadily on in a straight line we come back to tho point from which we started? Secondly, if the earth be a couifuuous plane, where docs it end, and in what, 'and what is it built on and supported by, as wo are invited to ubandou the theory of central gravitation, linked up with that of the spherical form of the earth?

To show that I (do not speak without authority, I may cny that I hold a certificate from examiners that "l'was a correct aud able navigator " aud that I have myself been "round the world," as well as up and down and round about nn many ways. I once, after being two months out of sightof land, sent amau aloft to look in a particular direction for au island, and in half au hour he called out " Land Ho." Now will any one in; his senses suppose that this would be possible ifj the doctrine on which we work were so fundamentally wrong that the world on which wo travel is utterly different In fwrm to what we suppose?

Wo do uot chatter nonsense, wo know that starting from Engluud, wo may sail west to America, cross that continent, go still west to Japan, China, India, and home, always westing, by the overland route. ".We know that we sail eastward to the Cape, to Australia, eastward still round the Horu, home again, coming north on our return as much as we ;went south on our outward voyage. We know also that if two people started a: the same time on such journeys, and returned on the same day, on comparing time, one would have lived two days longer than the other In the same time; for one, prolonging each day by accompanying the sun, would in the complete journey have thus dissipated one day; while the other, going always to meet the rising sun, would have seeu it rise"aud set,once oftener than if he had remained iu one spot.

It is true that in travelling over a wide plain, it is quite possible to keep going round and find oneself where arte started. I have done it myself on a cloudy day, but it would be impossible if one kept a straight line, or went by compass; for eveu If we imagine that the sun. Instead of following an apparent etraight path, due actually to the world's own rotation, winds roand the circumference of a great plane, a motion somewhat hard to reconcile with farts, and that we thus follow it aud return to our stnrtiug poing, we have still to get over the magnet, and explain how It guides u* in this extraordinary circular course, a thiug perfectly easy to understand by those who know the earth to be a

ball possessed of magnetic polarity, acted on, and being acted on by other magnetic bodies.

But it may be said that this only shows that the earth may be a long cylinder instead of a flat surface. Granted; but what sort of advantage would this idea be, having all the supposed evil consequences of the globular theory without one of its advantages. Nothing, however, is easier than to prove that the earth Is not a cylinder. If sailing east or west we carry an accurate watch with us, it will continue to show us the' time at the place \ we left; we soon llnd It does not. show us the time at the place we have reached. If we are ou the equator, we And that when we have thu» sailed viiu geographical mites, there is a difference of one hour, and this being one twenty-fourth of a day, is also the same proportion of the earth's circumference; or treating it ns an abstract circle, divided into 3ttti parts. It la 15 of these; that is, the difference of longitude is 15 degrees, the difference of time, 1 hour, the period during which this partof the circumference passes under tho sun. Rnt If we try this at another part, the cade is quite different; the more distant wo are from the equator, the less space we require to travel to make the difference of one hour; that is to say, the circles parallel to the equator diminish in actual length, and the cylinder on which they would be all equal passes Into a globe.

Hence, strange as It may soem, the nearest way to a place due north or south, is to follow that line; but it is not so with a place due east or west, except at the equator. In the north we must follow a curve tending first north for half the distance, and then sooth ; south of the eqoator, the reverse. This is what is called Great Circle sailing, and depends upon the fact that the shortest line between two points on a sphere is one which, if carried .through, would cut the sphere into two equal parts. This is called a groat circle. On the earth, akt tho north and south lines, or parallels of longitude, as they are called, though converging, are such; but of east and west lines, only the equator.

Time and space, the only realities or Infinities, bythe-bye, require me to conclude for the present.

Sigma.

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d = *J is x »4 = */ Hi =« 105 = 1—In.
10

Having shown d «= 1—iu., I now proceed to Rule 2,

wherein the multiple 30 should be 32. Thou the example b (by rule 2J will be

21 a

d -= ./ 32 x 14 *= J 44$ = — = 1 —
10 10

correct to the former rule, and not (as Mr. A. T. makes it appear correspond to his former erroneomt working) Uin.

To the converse operation make the application, and it will appear much more clear: a (by rule 1)

6a 36

— = — = 4J tons.
8 8

This is as given by Mr. A. T., and is correct Tlieu for proof with corrected divisor Z2. 0 (by rule 2)

12s HI 10

— = — = 4 4J tons

32 32 ' 32

4 correct answer as by rule 1, aud not 4— tons, as Mr.

A. T. shows it; for according to rule applicable to areas of circles, a chain twice the size Is four times the weight, hence a multiplier or divisor for 8ths being 8, muBt for 18ths be 8 x 4 = 32, proving the correctness of rule as applied in foregoing examples.

I am sorry to see Mr. A. T.'s remarks respecting ropes, which are also incorrect. I think he might with advantage have given us the modern experience of Huddart or Chapman in preference to Du Haunts 130 years ago. As, however, his remarks on this part of the subject seem unfinished, T forbear saying anything further at present, as mv desire is only to put matters correctly for the benefit of your numerous patrons, and trust this will be received" as given, \V. II. Laidlkr, Edward-street, Bow Common, K.

SILVEKIXG SRECULA.

Sir,—About three months ago I commenced the grinding of a speculum for n telescope of tho Newtonian form, and following the admirable directions given in your columns by your able correspondent Mr. Purklss, 1 believe I have succeeded, only 1 have uot been able to get it tried as yet. I have likewise made a diagonal plane of a piece c fine plate glass, as recommended by the same writer, This I have attempted to silver by the Rochclle salt method, described in the Mechanic some time ngo, but havo not been' successful as yet. I have attempted this method in preference to that one described by Browning, as 1 see some of your correspondents have succeeded well with it. Mr. Thomas Woodruffe, p. 17. Vol. IX., says it is "quite equal to Browning's at one-tenth of the cost.** I got the crystallised nitrate of silver used for photographic purposes, and dissolved it In distilled water, adding ammonia ns directed, and stirring with a glass rod uutil the precipitate formed, when the ammonia was tirst added was dissolved. The solution thus obtained

was clear alter settling, but there was a dark sediment in the bottom of the bottle. I could not get crystallised llocbolle salt, but 1 procured the powder, and made a saturated solution o/tt. and put it in a dUh to evaporate, when, in > few days,'.i got beautiful crystals. These I dissolved in distilled water for the reducing fluid. I used tor the plane 30 drops of the silvering solution, and 15 drops of the Rochello salts, and cleaned it with longe and wash-leather. I obtained a film, but so thin In the centre that the gentlest rubbing removed it from the glass, while all round the edges it adhered ttrraly and took a brilliant polish. As the film in the centre of the glass only appeared nearly transpnrent, :md cloudy when held betweeu the eye and the light, it occurred to me that the cause might be the gluts not being sufflcisutly clean. 1 procured nitric acid, with which I rubbed it, and afterwards wajhed it to remove the acid, but with no better result. I tred both the silver and salt solutions double the strength—viz., 20 grains to the ounce of water, but still the same result. I have sometimes kept on the Bolutlon for some hours, adding more when nearly dry. by this means getting a thicker film in the centre; but then there was always whitish, rough patches, chiefly about the edges, which, no amount of polishing would remove. I should lee) very grateful If any of your numerous readers would help me ont of my difficulty, and point out where lAm in error, and advise me what to do.

Would Mr. Purkles, "F.R.A.S.", or any reader, kindly inform mo what should be the size of the tliagonal piano for a speculum of fifln. diameter, and twin, focal length ; or rather, I should like to know by what means it is known, so that I might be able to find for myself the size of plane for any size of specula.

I very much admire the telescope stand of Mr. Rlacklock, late of Manchester, now of Aberdeen. I am making mine of the Bame form; would he kindly describe his method of mounting the speculum. I should feel obliged it he would ascertain if glass -ui table for specula Is to be got in Aberdeen, as the carriage from the south comes so high.

I may mention that in grinding and polishing mv speculum, although I have followed the directions of Mr. Purkiss, I have not used a machine, but worked It entirely by the hand. I have, however, devised a means which I believe to bo original, as I have seen no notice of it, by which a regularity of stroke with careful manipulation Is insured. If my speculum turns ont well when tried, I shall be happy, with your permission, to describe It for the benefit of such of your readers who, like myself, are unable to spare much money for such a purpose.

James Goat, Beauly, N.B.

THE "VBL.OCIKERE."—Having read a letter from Mr. W. H. Reveley in your last issue. I am much surprised that the '• veloolfere" therein alluded to (a description of which was given in a former number of the English Mechanic) has not yet appeared before the public, as it it went only half as fast as described, namely, 15 miles an hour, with as little exertion as walking two or three, velocipede inventors need no longer rack their brains, as it ought to meet the requirements of the most exacting, and be invaluable te persons using such means of locomotion.—Tricycle.

EXTRACTS FROM CORRESPONDENCE.

THE BICYCLE.—" Veloce " says:—" PeBding Mr. Newton's decision at Worship-street Police-court, as to a case of a bicycle circling, I think it only fair to say that to circle about is a very dangerous practice to pedestrians. If a rider wiBhes to practise feats, he should do it In a lano, or some other place where there is no traffic. But it is not to that part of the Inspector's evidence I wish to call attention; he says, 'he confined himself strictly to roadway, but circled about and rode round at a great pace (eight or nine miles an hour).' Now, Sir, I wonder whether it is the eight or nine miles an hour that Is dangerous, or whether It is the circling about. I hope. Sir, that the magistrate's decision will not be unfavourable to the bicycle cause, for I think that as a means of locomotion, and a wav to vigorous health and muscular power combined, no "other machine can surpass it. If Mr. Newton's verdict will be a conviction, then I and others in the country will be open to conviction too. for it is only a nicecomfortable pace this fine weather to ride nine miles an hour. Sir, I see that in France a new paper^is begun, expressly devoted to the velocipede; why not in England? or devote a column every week in your worthy journal."

MR. BEARDSLET'S LETTERS.-Mr. J. Dyer ■ays ;_•< I lhave Been Mr. Beardsley's letters, but see but little in them calling for serious consideration. He appears to me to be objecting for the Bake of it, and seizing upon any circumstance wherewith so attack the truths of astronomy. Some of his statements^ire retailed from " Parallax." I will, however, attend to the gentleman, and if he advances anything worthy a reply, and no more able person should answer him, f will make some observations when he has finished his letters; at present it is difficult to getat what he believes, or what he is aimingat. He is an ardent advoc.-.te of the views of "Parallax." and has written a book entitled 'Theoretical Astronomy Examined and Exposed,' of 128 pages. It is made up of dogmatic assertion and most disrespectful speaking (in some places almost amounting to abuse) of some of the best and most learned men of the day. He is or was a printer at Greenwich, and has sold the copyright of his book to Hampden. Mr. Hampden has also bought the copyright of a book published by "Parallax," entitled the ' Earth not a Globe.'"

THE PATENT LAWS.—" Beaten," states:— " For watt of means to patent, I have for about two years nursed a loco-manumotive power. My ambition Is to patent this power in England, Franco, and the States, and here comes the rub: the wealth of England has had Hie making of England's laws, of course they are made for the benefit of the wealthy class; the i'ateut Laws among the rest, the A B C of which is, that if a man can muster £40 within 6 month", he may have a patent, and this Is exceedingly nteresting to an inventor, who deems himself a lucay fellow if he can muster the price of 401b. of potatoes when wanted, and with glowing admiration he contemplates the paternal, patriotic laws under which he lives, when he compares tbem to those of despotic France, or republican and Democratic America, in either of which he may patent his Invention lor comparatively an •old song,'be well protected in his rights, when obtained, and their defence and redress easy, if infringed. With reapect to the English patent, my difficulty is, how to satisfy a capitalist without Imparting the secret? Will any brother reader sugge el a method, I confess that In this I am fairly beaten.

/ REPLIES TO QUERIES.

[lOfiO]-SMALL FURNACE.-"C. R" can convert Napper No. 2 fire to answer his purpose if he hnB a fan, or by using Dorset liquid fuel. If "C. R." has not seen any of this fuel at work, I will send him a sketch of it.—Geo. Stuart.

[2270.]-GRANlTE POLISHING.— The granite must be first dressed as level as you possibly can, as that saves a deal of polishing, it being naturally a hard substance; then well rubbed with fine sand and water by an iron plane, until the tool marks are completely rubbed out, when it must be all clean washed off. Next apply No. 0 emery with water, the same as the sand, with this difference, the emery must be rubbed until it is reduced to a " sludge." It Ib beitei to have a frame about fiin. round the stone, and the joints closed with stucco, as that prevents it from losing: the quantity is Jib. to the square foot. Wash clean down again, and finish with putty powder (oxide of tin), applied on a felt attached to the bottom of the plane, taking care the felt do not glaze, else it won't bite. If the granite be very BOft, flour emery will be better than No. 0.—W. R. M.

[2408.— METRONOME.—For reply, see letter, page 161.

[2461.]-INHALATION OF IRON DUST.-Might not" Turner" contrive a kind of bellows with double tuyere to Wow all dust away from his lathe, similar to the bellows used by the.pointers in many needle mills ?—John D.

2502.—CIRCULAR DISC—This can only be done approximately, and in doing so, Bupposealine representing the radius of the orifice, the ends of which are the centres of the two ciroleB representing the orifice and disc. Raise a perpendicular at the distance of \ of the radius from the centre of the orifice, which will cut the circumference of the orifice in a point where the two radii meet. Let p be that perpendicular, which is also the half chord of two arbs, standing on the opposite aides of the Bame base. It alBo represents the Bine of half the central angles. From which we can find the areas of the two segments, whose sum is equal to the half area of the orifice. From the properties of the circle

f r \* 8

heat. I use an old jug and the oven of the kitchen fire after tea. This gives a powerful light, but would, 1 fear, be too expensive for general use.—C. Ward.

[2521.]-CUR10U8 AFFECTION OK TilK. TEETH. —The deposit is called tartar, and consists of salts of lime and organic matter from the saliva. To prevent Its formation the teeth should be gleaned twice a day at least with soft tooth powder ipVoolpitated chalk Is the best) and a little soap. When-tartar has accumulated, it must be removed by the scaling instrument* of the dentist.—J. M. K. E.

[2528.J-MUSICAL BOX.—The construction is very simple. A side-toothed wheel, on the axle of whicb l» fastened one end of the winding-up spring (which is enclosed in a small circular box on the left), is put in gear with one end of tho roller, on which are fastened the fingers or pins which lift the teeth of the comb, from whence the sound comes. The motion Is regulated by means of a small fly-wheel playing before the spring-box (which, by-the-bye, goes out of sljrlit

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the approximation to be nearly right. But in praotice, the whole amount of labour is reduced to tbis simple fact of adding to the radius of the orifice, l-6th of Itself for the radius of the diBC or more nearly as the JM-.JiS.—R. D., 93, liroughtouBtreet, Edlnbro*.

[2503.]-WEIGHT OF WATER.—A cubic foot of rain water at 60° Fah. welgh»997l37oz. avoirdupois. The average weight of sea water at tho Bame temperature is 1025ozs. ; that of the Dead Sea 1210oz. The temperature of greatest density of rain water is 38° 8, and between that and 02° It varies but one part in one thousand. It is generally assumed (for convenience of calculation) that a cubic foo*. of rainwater niss-'-S Fah. weighs luOOoz,—Brother Teh.

[2506.]—CAMPHORATED COLZA OIL is prepared by dissolving IJoz. of camphor, broken up lnt» small pieces, in one piut of colza oil, by aid of a gentle

during business). This fly, standing upright an* having a thread round the stem, is acted on by ti..ur wheels, which are lu gear with the end of the roller. "Omar" will find on the top of tho Bpring-box what is called a "Geneva stop," illustrated on page 53 (No. 12 being marked in the corner) ot'the preseut volume. The right end of the roller comes slightly over the edge ci the same, and is caught in a slit in a small lever (worked by a pearl button outside), which mover the roller up and down Its axle, thus altering thetune or position of the pins. The left button stops the revolution of the rolSer by the end of a lever turned like the letter L popping into a hole in the roller-wheel at the end of each tune. And uow I must beg our Edi. tor's pardon for taking up so much space in trying to explain the "gutsT" of a musical box.—Habry Bertram.

[2534.]—ERRATUM.-The diagram given with the 3rd solution of this query belongs to the reply of "Gregory," page 13U, Q. 1935.—X. X.

[2548.1-G1LD1NG BATTERY.—" One in a Fog" has charged his battery wrong, to commence with. 1 part acid in 12 of water would be better than 1 In^. The sulphate of copper should be suspended in toe upper part of the solution Instead of the bottom; but the main caUBe of failure Is that be is using cyanide of potassium instead of aurocyanide. The cyanide must be charged with gold before he will get a deposit If he persevered, this would be effected by the action of the battery; but his globe surface ought to be large.— Sigma. .

[25501-ETHERIAL GOLD SOLUTION.-Tbis is applied simply by brushing over the Bteel surface, or by writing with a quill pen. The steel req"<"» n<> preparation beyond its surface being clean and bright. The deposit is a mere film, which will bear little lrlctiou.aud canuot be thickened by this Folutlon.-SiGM v. f'558.]—SUN-DIAL.—The following is a good method of setting a dial :-Set the dial by the sun at mid-day as correctly as possible. At nine o clock on .-. bright morning set your watch by the dial. At three in the afternoon observe the difference between the dial and the watch, and correct tho dial for half the difference. Proceed in this manner day by day till they agree perfectly. Observe, however, that the equation of time must be taken Into account, and set your watch fast or slow, as may be necessary.— J. M. K. E.

[2558]—SUN-DIAL. — Tbo simplest method of obtaining a truo meridian line for a sun-dial is from, the Ordnance maps, on whioh the lines of longitude are accurately marked, and the Greenwich mean time, which is telegraphed dally to most towns and railway Btations. If you Bet your watch by the Greenwich time, aud then take your longitude from the map, adding or deducting 4 minutes in time for every degree, and 4 seconds in time for every second of longitude, as your place is east or west ol Greenwich, if the sun and clock are together (which is only tho esse on a few days in the year), you will readily obtain, your meridian. Thus, the place I reside at Is 0 48 west of Greenwich. This is equal to 3 miouteB aud 8 seconds in time; therefore, on a day when the sun ami clock agree, when my watch shows 12b. 3m. bsoc., tho sun will be on tho meridian. Of course tho equation table is necessary at all other times.—Anon.

[2559.]-ANTIQUE.-If "Vlvus Sperandum" will send W. Nelson Last, Bury St. Edmunds, an impression of bis cornelian ring per post, he will (through tho English Mechanic) give him the Information he requires. The art of polishing the engraving is not lost; but It is only the best engravers that attempt it. P>M5 ]—HERBAL OF THE BIBLE.—" Ixion" may obtain " Plants and Trees of Scripture" of the Religious Tract Society, Paternostcr-ruw.—W. C». Raybould.

[2595.] - HERBAL OF THE BIBLE.-" Bible Natural History, containing a Description of Quadrupeds, Birds, Trees, I'lauts. &c, mentloued in the Holy Scriptures." By the Kev. F. O. Morris Published by Grooinbridge £ Sons.—Worring Woman. [2566.]—TOOTH POWDER.—Armenian bole is thebost and cheapest tooth-powder to be had for keeping the teeth fresh and white. Twopeouyworth will last for Blx months. It is of a reddish colour, and sold at any respectable doctor's shop. Use the least quantity

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on tootb-braeh every morning with freak, ooId u ,\u r, and In a few daya it will make the teeth beautiful.— fraREttT Millar, Glaagow.

r2567.J-CHIMING CLOCK.—If "Toodlea" will take out the old cords of his clock, and put in stronger ones, or catgut, he will find this much better than nut tin*? a hay bag in the bottom of hia clock-caae.— D. 11. S

Li67t.J—iKOLIAN HARP—In answer to "R. B.," I have much pleasure in giving him all the information 1 can. It la constructed of very thin yellow pine. The length equals the breadth of the window, the depth about 4in., and the breadth about r»in. There is a bridge at each end of the box like the bridge of a violin, with screw pina in it. for relaxing or tightening the strings. The atrings are of the finest catgut, seren, ten, or more, all tuned In unison to the same note. There Is a circle Hin. in diameter drawn on the top ot the box, exactly in the middle, underneath the strings, which is pierced with small hole*, to act as a sound hole. Place the instrument in a window and draw down the aaah, which will force the wind over the strings and cause it t*» sound.—Valve. P.8.— Many thnnks for the insertion of my query, 2562, No. 2W. but there are one or two typographical errors in it which will make it rather hard to be understood. Perhaps you will be so kind as to inaert the following correction :—" Reed hibs" should be " ree*l holes," and "accident" should be "accidentals "—that is, sharps or flats that ocour in she course of a piece of music.

[•2579 j — MALLKT.—If "Anon" wants to make a. pattern for his millet, the following will give him all the information be requires:—Let him make a block of wood the size of the shell (outside size), and nail a piece of wood on each end the inside size of shell, about ljln. thick, and nail two pieces, one on ton and the other on under side, the size of hole reqi irei for shank, and about lin. thick, the top one being larger than the other, to form a taper. Those are culled prints; they leave an impression in the sand to boar the cores. He will nave to make & core-box the size of inside size of shell, composed of two aides and two ends, it being a frame the size of the core (inside size), with a hole cut through each side the size of small prints, one larger than the other, with a piece of tapered wood at through them, to project about l<Jin. through each side -, must be left loose to pull out. Make the core-box the eame length ae the block and the two large priuta. A diagram will greatly assist

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[25»i.]—BORING WOODEN HANDLES.-I suppose, from "A. B V question, that he has many handles to bore, and In that case a half-round bit, or a short piece broken off a carpenter's nose-bit, and soldered into a small brass chuck to fit into the centre hole of the poppet head, would be a good way ot starting the holes. The handles should be held either In a clam-chuck, or be supported by a collar plate. I always use a common gimlet, taking care, however, not to work it as you work a cork-screw—viz., holding the bottle still and turning the screw round, but holding the gimlet firmly In the right hand, and letting the tool handle shift at each half turn In the left

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hand, as by this means you can feel whether it is running straight down the middle or not, and with a common gimlet you can apply force sideways to scoop the hole when you find any tendency to running out The usual way Is to burn the tools Into ttieir handles, and I see no objection to the practice, provided, first, the hole has beeu bored deeper than the point of the tang of the tool will ge; nnd, secondly, that all the charred portion of the wood is filed or scraped out of the hole before driving the tool finally in. If the tool is thin, with a broad tang, like a Lancashire file, it will burn its own hole too wide in the narrow direction, so a thinner tool should be nsed to do the burning. A much better plan is to have two or three floats, or small taper flies, cut on one side, and one edge only, with a few coarse teeth, and one or all made to cut backwards, for getting out the holes to suit different dimensions of tangs. Almost any old tool that Is small enough will do to make them of, and the notches may be, and are better for being, as uneven as you please; and the tool need not be hardened, or If gardened, should be lowered to sawtemper, so that you can easily sharpen It with a file. The best wood for handles is ash. as it does not blister the hands. It must be well seasoned, or the ferrules will drop off, aud a dressing of linseed oil and yellow ochre, with alkanet-root to give a fed tiuge, should be smeared on, and allowed to dry on for a day or two, before giving the finishing rub-off—J. K. P.

[2598.]—LKVDEN JAR.—A charge might be given by means of a glass rod, but it would be a tedious bu»iness, and not much satisfaction to be got out of it when accomplished, by means of frequent rubbiugand application.—Siom A.

[26(M.]—PROBLEM.—To draw a olrcle passing through two given points and tangent ts a given circle. Let O ne the given circle, and A B the points. Through A B draw a circle cutting the first, hence C. D, and E. From E draw a tangent, to circle O, and the circle passing by A, B, and F will answer the problem:

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cumference In G, the point of contact for the required circle. Join E G and G F, each of which bisected aud produced will out In H. H G will then be the radius of the circle required.—H Attar G. Nbjvton.

[2000 ] -DAWN, Ac—The periods of day and night are caused by the earth's rotation on its axis. 1 he change from day to night and from night to day takes place iu the following manner:—The sun enltghteus only that half ot the earth's surface which Is turned towards blm; and as the earth successively presents different parts ot its furface to and trotn the sun, these parts must iiave alternately light and darkness. At the Equator the day and night are of equal length during the year—t. r., 1J hours each. At the Poles the day and night are of equal length during the whole of the year; but there is only one dav and one night, each being six mouths in duration. The dreary winter

of the Polar regions is relieved by reflected light or twilight by auroras, and by the full moon. Other reasons for these cbauges are, tho earth's annual motion round the sun, and the earth's axis being Inclined to the plane of Its orbit. Hence, Hudson's Hay Territory, Greenland, Lapland, Siberia, will have the longest starlight.—R. Wilson.

[2604.]—PROBLEM.—(By the kindness of a Professor of King's College^London). A is the centre of the given circle; B and G the two given points; bisect iJ C and draw li G perpendicular to B C; then the centre of the required circle lies somewhere on the line H G (produced if necessary). From an arbitrary centre H, draw a circle through B and 0, cutting the

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given circle in D and E; produce C B to F, and draw E D produced to F; draw F K tangent to given circle, and from A draw A G perpendicular to F K; then G. the point of intersection of II G nnd A G, is the centre of the required circle. P.S.—Supplementary. —If the tongent F K is drawn to the lower side of 'fie given circle, and the diameter drawn at the point if contact, and produced till It cuts G H produced, then the required circle falls outside and embraces the given one.—J. K. P.

paoo.l-OLD COIN-—Roman. Readi VESPASIANUS and JUDAEA CAPTA.—Collector.

[5619.]—OLD COIN.—The pioce found by "X. I. D." Is a coin of Vespasian, Emperor of Rome from A.D. tH) to A.D. 79. On the obverse there is the bust of the emperor, with his name and titles. Reverse, a foraale figure, seated, weeping, under a palm tree ; a Roman soldier, standing, behind. Inscription: IV DAK A C APT A i.l ud.Ta taken). Tho letters S. C. appear upon nearly all the Roman brass coins. They stand for Senotiu Confute (by decree of the Senate), because all the brass coinage was under the control of the Senate. This coin was struck in commemoration of the subjugation of Judaea by Vespasian and Titus, and of the total destruction of Jerusalem, A.d. 70. It is rare, and the market raluo would be between 10s. and 15s. It Is a very famous and interesting piece. —Henry W. Henfrey, M.N.S., Ac, Ac.

[2631.]—CUTTER BAR.—In reply to "Foreigner," I made one of these to the design of "D. H. G., and had to make the same complaint of it that he has. "D. H. G." very kindly told me that the cutter is shown In the drawing projecting far more than it would be In use, for that it was meant for a lathe whose centre line is 9-10th inch above top of slide-rest. I think the crank might be a little longer without doing harm.—J. K. P.

[2621.1—PROPORTIONS OF SPACE.—The volume of a sphere = volume of the cube constructed on its diameter x 0-5236. The weight of lead shot that can be packed In a given case must necessarily vary according to the diameter of that shot.—B.

[2624]-PROPORTIONS OF SPACE.—TO "MECHANICUS."—One single sphere is 5236 of the surrounding cube; but if you have a number of spheres, and put three of them together in a triangle, or four in a rhombus (not a square), and go on packing others roand them, each ball will stand in the middle of twelve others equidistant from it and from each other. It may be proved that each ball occupies ou an average -707 of the cube of its owu diameter, while the ball Itself is only the -52.10 of that cube, or what is the same thing, the ball would occupy only '5236 of the -'hole space If we started packing with a'square in the middle instead of a rhombus.—See Denlson's "Astronomy without Mathematics," 4th edition, p. 266.-J. K. P.

[2629.]-THE QUEKETT CLUB.-Aliow me to inform Ed. H. Jones that the "Journal of the Quekctt Microscopical Club" is published quarterly, price one shilling, by Mr. Robert Hardwicko, 192, Piccadilly, London, W., from whom your correspondent can obtain information as to the means of obtaining the journal in Bristol.—W. H. G.

[2631.]—SPHERICAL FORM OF THE EARTH. —The reply to "Ajax's" question depends upon the form of the bottom of his cistern. If it was a true flat, such as an instrument would make, or a level would show, it would apparently be hollow in the middle, and water would remain there long after it had run off the ends. In that case the water would be deepest in the middle; but if the bottom was a level like a billiard table, on all parts of which water would alike rest, It would be a curve, and the depth of wator alike In all parts. The extreme idiocy of tho arguments, as their utterers call them, set forth on this subject is really too much for people who know anything of the matter. No intelligent human being who really has examined the subject could entertain a doubt about the spherical form of the enith. It cun be measured even in a long building. If the two ends are truly vertical, a measure taken along tbc- top is longer than one along the ground hue.—Sigka.

NOTES AND QUERIES.

[26373—ELECTRIC LOCOMOTIVE.—Will some kind brother inform mc how to construct an electric locomotive engine, to run on rails by electricity 7— K. F. D.

[46.18/)— MAKING BUTTER,—I Ьлте heard there is an easier way oí mäkln? butter than churning-; can any reader tell me how It le dune?—Cambridgeshire. [2639.]—OPINIONS WANTED— Perhaps -some of your numerous readers will be so kind as to give me their opinions about the сайке of the following :—A short distance from here are four horizontal engines, which are used for drawing coal; one steam valvo is common to them all four, likewise one lever for reversing them. In lowering down the pit they have full steam, about one-third of the distance, then it is shut off, and the lever brought into the centre notch, which ought to close the ports, but the pair of engines to the right baud still continue to exhaust, and those to the left do not. If some of our Intelligent men will give their opinions as to the cause and its remedy, it will! perhaps benefit others as well as myself, for I know that when the engines were made, It was intended that they ehould not exhaust at all In lowering after one-third of the distance, as It is a shaft where they have only oue rope going—John W. Bedford.

[2640.]-GIRDER PATTERNS, Ac—In makln« patterns for girders, gutters, Ac, that are stronger at the bottom than the side*, the pattern has to be made round, so that when the casting cools, the contraction draws it straight. Will some practical man be so good as to give a rule for calculating how round to make nny girder, gutter, backstay, or anything else of a similar character ?—Johk W. Bedford.

[2641.] - MEDICAL COIL.-(Page 513.) -Will "Sigma " kindly explain what he means by saying, "solder 2 to N.battery pole," and further ou he says, "load 2 and 3, and any other euds, to screws at the other end of board." Is this correct, and if so. please say how it is to be done, that is 2 at both ends of the board and different screws, and also the best kind of battery to use.—Unlearned Man.

[2642] - FISHING BODS.- "The Harmonious Blacksmith " says he has had consideraba experience in making Ashing rode; I shall be very pleased if he (or any other practical gentleman) will give me a few hints how to make a useful rod, about 14 or 15ft. long, the best kind of wood for each piece, how to put the ferrules on, and any other information that he thinks would be useful.—A Young Tyke.

[2643]-IRON PRISM—A equarepriem of malleable Iron, whose leDgth is equal to four times that of one of its sides, Is to be rolled (or flattened) into a square plate of uniform thickness, such that its whole aupcrfices shall just be equal to It« solidity. Required, the sise and thickness of the plate, the solidity of the said prism being 2916 cubic inches, allowing no waste in the metal—A Middletonlan.

[2614.]—ADULTERATION OF TURPENTINE — Would some oue Inform me how I can best, or at all events easily, ascertain whether turpentino is adulterated ?—Basis.

[2645.]-IMPERFECT TWO MANUAL ORGANS. —I ehould be obliged If any of your readers would enlighten me upon the following:—I have a two manual organ, and am sorely troubled with the reed stops being so often out of tune in the swell organ. The reod stops are cornopean, clarion, and oboe, but the clarion is the one that gives me most trouble. The oboe keeps pretty well in tune, but Is very slow In »peaking. The reason of the reeds not keeping in tuno is, 1 am informed, that the pipes and tongues are nut made iu proportion to each other, and that to remedy this would he almost as expensive as having new pipes. I wish to know if I am correctly informed as to the cost, also what would be the cost of a set of flute pipes to replnce the clarion, and the cost of applying them ?—Anti-discord.

[2040. ]-G IL DING PLATE GLA88.-How do glass sign writers gild the back of plate-glass, after the letters are written, and rice vena f—Blackburn.

(2647.]-COLOURED PRINTS FOR DECORATION.—\V here can I buy those coloured prints which, when steeped in water, may be laid on to any smooth work, and the paper on which they are printed slid away, leaving the print firmly attached to the article operated upon 1—Blackburn.

[26-18.]-CARDING E.NGINE.-Would " B. W. R.,'' oreóme other brother reader, please Inform me, through the medium of our highly-esteemed journal, which, lu his opinion, is the best carding engine at present in operation, and that has the most modern Improvements? И accompanied with a drawing, perhnps the matter would be rendered still plainer. I believe the carding engine in general use In tho Manchester and Bolton district, is that to which tho American pateut automatic movement is applied. Would he also «ay what, in bis opinion. Is the best appliance for grinding the main cylinder and dofTer.and what is the difference effected between using the ordinary grinding strickle and the patent grinding pulley, which is worked from end to end of the engiL« by means of a spiral groove in the shaft ?—Excelsior.

[2649.J-FIANOFORTE.-WI1I the "Harmonious Blacksmith inform me of the following questions viz. :—1st. How are the holes that the lever wire works through, which lift the damper, bushed? 2. How are the same holes bushed In the hammer butts' —.4. L. Moffatt.

[«MO.J-fo "F.R.G.8."-MAP PROJECTIONS —I shall feel much obliged if you will tell me the method of projecting a map on the gnomonic projection, having any given place, say London, in the centre, or if the J

[ЯЦгЛ-SULPHATE OF ZINC—Will any correspondent Inform me how the sulphnto of zinc of commerce Is manufactured ?—Telob.

[2653.]-CIIKMICAL SOLUTION—I have a solution composed of sulphuric acid, tea «alt and water, in which a quantity of zinc has been dissolved. Will an) correspondent tell me what the precipitate, which hacheen formed. Is ?—Telos.

[2554.]—METRICAL ACT,—Of what date is it? Does it not give the exact reduction of English weight* and measures into metrical? I pronoec to querists to employ only the letters A. K. W. for "A kind answer will oblige," or rather to add nothing and always (which is the case) suppose this phrase understood ?—John D.

[2655.]—ARCHER V.—I am about to purchase a selfyew bow. Would some brother archer kindly give me his advice as to how to choose a suitable oue, as to strength, Ac.? I have shot for two seasons with л hickory backed lanccwood bow, of 461b. tension, which has an unpleasantly sharp pull, but is not too stron" for me. Ought a self-yew bow to be stronger, If so, how much? Is there a good modern book on archery!

—YOUNG TOXOPHILITa.

[2656]—BOOKS—Can "Sigma," or any other of our numerous readers, recommend a good book on practical electric telegraphy? I have made inquiries at several booksellers without success?—Much In Want.

[2(W7.]--FORBES KNITTING MACHINE—Might J ask, through the medium of your journal, Forbe«, Bros., and Co., of Glasgow, to give a more detailed account ot their knitting machine, illustrated in No. 2ol of your last Vol., feeliug sure that many of your readers would like to see the same ?—VioiE.

[2658.] - OBJECT GLASS. - Would any of my brother readers kindly give me a little information whether 1 could get a stronger object glass for my telescope, which glass is lin., and if I could see distinctly without altering the other glasses in the inside > —Ignoramus) 2.

[2659.]-ABTHONOMICAL BOOKS—Would some reader kindly inform me where I could obtain tho best aud most authentic elements of the planets' orbits including the asteroids, with price ?—D. Jenkins.

peeeo-LEO'S VELOCIPEDE,-Will " Leo." whose velocipede appeared In the Mechanic, No. 218 Vol IX, gives a description of the lndiarubber springs which bring the pulleys back to their first position • how are they fixed, what size ehould they he and will he give a description of his ratchet work 7 Can

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[26, >.]-DRAFT WANTED.-We are short of a draft at our works to keep our stenm up and there is a large chimney, distant from boiler Si yards Will «..me one of your numerous readers inform me of the be» means of carrying the flue underneath the ground thatdistance, and if it would be an effectual means of attaining the desired end ?-П. Gregorieff

[267* ]-CASTING SILVER BALLS—Could any of my brother readers Inform me of a better method for casting silver into small ornamental batt them in sand fas I do) they come out so rou-'lT want to avoid. I have tried plaster of Pari» 'but 4 part ones come; is it tor want of ventilation' or wh and how is it to be done ?—Castor.

[26-4]-CLEANING WHITE CORAL.-Can « reader inform me how to clean white eoral, and restorV it to its original beauty, after being exposed to th.. dust, which has made it almost black?—Inquirer. . [2675.]-POLISIIING WATCH PIVOTS—In polishing a pivot with a square shoulder, what is it that Dtoducee those cuts or ridges in the shoulder ? I have hear-i t attributed to several causes, hut never could lean, the exact cause or motion which produces them • ш>г haps some practical watch pivoter will give the W Plan for preventing ridgy shoulders, and so help« young beginner ?-C. R.'

[2fi70.]-MODKL STEAM ENGINE.-Some time¡ÜT.1 ,a1w1.edTm,»ed, » «TM»11 model vertical engine with a spirit lamp underneath to raise steam - accord' tng_to the drawing_ there seemed to be a cylinder and piston that turned a »mall fly wheel on tie top • thprice, I believe, was 4s. 6d. ; can any brother subicrrtJr give a drawing of the model in question. Hhowin? nowmotion is produced by steam in so small an enpae?"

[2G77.]-HYDROGEN GAS FOR BALLOON.Mould any reader acquaint me how many cubic ten of carburetted hydrogen gas is required to float a hum« being of eleven stone weight, in our atmosphere ■ al" ga^-HENRvTuTT "* to «»"У'01« diurne of [207Ч-ТНК "HIGH PEAK" VELOCIPEDE-Can any brother reader give me dimensions, Ac., to em ble míi£h'Л.* th"*-wheel velocipede, known as tie • High Peak velocipede (an llluetratlon of it appea-ed n the Mechanic some time ago). Perhaps some brother reader wonld also kindly give hisexWwo as to the capabilities, Ac., of thf iboîeSTM

[2(179]-UNANSWERED QUERY -CLTRLIV«

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[2661 1-GALVANI81NG CAST IRON.-What is the bath composed of for cleansing cast Iron for galvan Is ng, and of what is the galvanising bath itself

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be description would be loo lengthy, I should be glad to know the name of nny book where 1 cuuld Und an arcount of the method ?—J. M. К. E

[2651.] - LECLANCHK BATTERY.- Will auy brother subscriber till me how to re-churgc the porous cell of a Lecbnehe battery. Those in ray possession are patent cells, made at Silvertown by the Gutta 1 erchu aud Telegiupb. Works, Co., Limited—Tilos.

'VE*B' i ¿an any subscriber give a goad practical rnl-*fnr*iwn!'

[2.-321-WATER METER-Will anybrother reader I Pl"K »mule? A drawing of the rail would be of ïooi
be kind enough to give me a full description of a high | service in pointing out parts of the rail likely to effect
pressure water meter, Its construction, and the action »be shape of the cop ¡ for instance, if I bad a rail this
of the water in passing through it, how it is measured,
ate.? The one the water company furnishes me with
registers four and five times more one quarter than
another, and I can affirm that tho quantity used is ae
regular as possible ?—Fines Achates

[2663 J-O.UIÇKSIL VER. -Will a brother reader
furnish me with a solvent for quicksilver? I acci-
dentally epilt some over some watch wheels, and want
teclean them; and If what will do for the above will
it do for plated jewellery ?—Fidus Achates.

,2664.]-ARM CHAIR.-I have an arm chair, the
leather covering very much faded, but in good con-
dition; can any one tell me how to stain it a maroon
colour?—Excelsior.

..r^O-INDICATOR-I should feel exceedingly
thankful if any one would kindly give instructions for
constructing the Indicator used with induction colls ?—

[2Ü66.]-COPPER DEPOSIT ON CAST IR0N-
I want to get a deposit of copper on cast iron; will
-ST Ves Г У 1Díorm me wnat «hemicals to use?

[26670-PAINT TO COVER TARRED WOOD.Can any of your readers recommend a paint or coatinir to cover tarred posts? It would have to adhere to tlVe tarred surface and to resist the tar oozing through it In summer. Colour must be light, as it is to make

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shape, A, and I altered it to this shape, B, what would be the result iu the shape of tho cop »—oldham.

[2082.]—TO THE REV. T. W. WEBB,—In theEnglish Mechanic of April 15. Mr. T. W. Webb mentions, that he was successful In separating Z Cancri, so recently as the 31st of March last. Will you permit mo to ask him to give, in an early impression of your paper, the observed position, angle, and distance between this close double? I ehould also feci much obliged to him, if he could uive me the result of any observations he may have made on £ Hcrculis during the last six mouths ?—О ч Ron.

[2083.]—IRON PALLISADINUS. — Will any reaJer kindly inform me how leng Iron .... I Headings, painu>d_ varnished, and bronzed, stand th ■ weather ?— W. A. J.

[2684.]— ENGINE CHIMNEY. — Perhaps some of your kind readers will give us the proper size of an engine chimney fora boiler, 2.1ft. in length, 5ft- in diameter, as the one we have is far too small: also, if we should consume any more fuel with a larger one. and is there any rule for calculating the size of such chimneys? The furnace is 6ft. by 4ft. Oin., with a flush flue? —A Subscriber.

[2685.]—AMATEUR TURNERS' CLUB.—I and my brother have just heard with pleasure that there I« an amateur turners' club come into existonce: will some subscriber give us all the information respecting it they can l- M. H. Hi Me.

[2686.]—ARNOLD'S CHIMNEY VENTILATOR— Can any of your numerous readers inform me how tobalance Arnold's chimney veutllator? A sketch will much oblige ?—Ironfounder.

[26870-DUST1NG BRASS MOULDS.—What is the best thing to dust brass moulds with, and why should not charcoal do ?— Ironfoundbr.

[26880-RENDERING WOOD INCOMBUSTIBLEIs there anythlag that will prevent wood from taking fire, and if so what, liquid or otherwise?—IbonFoundeb.

[a*«.]—TURBINE.—Can some reader give в sketch and explanation of the best form of turbine to work horizontal shaft, which takes about i h.p. to drive, siae ot inltt uud outlet, or makers of sameí—SiMPLETom.

[26*.\]-ALGEBRA.-Mnn.v thanks to kind and «Mo Mr. Honfrev, for Ins response to my query »bout tno planet Neptune. Whatever you do, don't weed your

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straight. I hive hung them in hot rooms, but they buckle, and arc dried very irregular; and 1 have also tried them In я baker's oven, betwixt »lutes »f galvanized iron, but that would not do, as it only dried the edges. Or if you could inform mo If thero are any books published on the manufacture of pasteboard? I know it can be done, for I have seen pasteboard perfectly straight and hard, but I cannot discover lu what mauner it Is done. Any information on the above subject, will be thankfully received ?—Thomas Gris*.

¡3704.]-TO "BUSY ВЕК."—In your reply to my inquiry for waterproofing paper, it states, lozi of gum nitric. 1 have Inquired at several houses for it, and the answer le, that the article is not known, and tbey think it mnst be a misprint. Can you inform me as to the above?—A. Speight.

[3705.1-COLOURS FOR GLASS PAINTING..-I shall be very grateful to any of your readers who will tell me of a rich transparent permanent pigment, in crimson, brown, i е., port wine hue; also, a pure bright yellow. Crimson lake, with the admixture of burnt sienna and umber, yields tho colour in all depth and brilliancy, but the crimson lake is sucha vanishing colour, that I doubt if the browns would render it permanent in continual 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 art of wiidow painting, I do not mean the modern staining and mosaic patchwork. Ihave been a paluter of dissolving view» for years, but I ehould be thaukful if you could assist me in the former matter ?—Sable.

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USEFUL Aim SCIENTIFIC NOTES.

Пгусееоп, Bros., under «rand-board. When the bellows ore blown in a jerklug manner, or whon the iustrument 1» played, these move backwards and forward» Very quickly,—W. J. RATBOUbD.

rî*9î.î-BOTANY.—Wanted a plain description o' the hedge mustard and cuekoo flower г—Nom Alumni. [MM.l-KEEPING COPPER PLATES FLAT.— \Y ill you, or any of your readers, iuform me how to keep thin copper plates perfectly flat, in continually passing through cillender rolls; they pass through about 15 together, and the average size is 24in. square. -C. H.

[2ЙН.]—GREATER PTHAH. —Can any of your readers tell me what is meant by the " Greater Pthoh 7 —Jiihoiaim.

[2095.j—GEOGRAPHICAL.—Will «ome one be so good as to tell me what is the meaning of key in the words, netherset-key. key-house, key-spink, in the neighbourhood of Madeley, Staffordshire ?—MINNEHAHA.

[2в!РЛ.] — CLEANING FLAGS.—Can any of your readers suggest a way for removing tar off flags, placed there by street advertisers ?—Minnehaha.

[2OT.]—CANARY.—What Is the belt treatment fir a canary suffering from " wheezlness "?—Minnehaha.

WMl-MfLL AND FORGE WORK.—ROLLING. —Would some of my brother readers inform me of a hook treating on mill and forge work; alsi, if some kind friend, who understands rolling, would tell me what speed per minute the following rolls should runviz. -. guide rolle, merchant ditto, and forge ditto ?—

A SlBBCuiBF.K FROM THE FlRST.

[2aW.-CROQ.UET RULES—NAPKIN RINGS,— AVherecan 1 obtain the latest rules for croquet; also, how can 1 mark boxwood rings so as easily to distinguish one from another ?■—W. F.

(ЯГИ).)—DEVELOPERS.—What are the best developer» to use for photoGTaphingdesfgns and paintings« also far portraiture ?—W. Crawley.

.iroi.J—KOLA NET.—Will "Bernardin;" kindly Inform me where the kola nul Is to be procured in London, and the price? I am reading up for a stiff examination, and shall be glad to try Its restorative powers, after fais plan, described in the Mechanic of March 12.—GADonA.

ri:«.]—INLAYING FANCY WOOD—Will some brotlicr reader describe fully tho modus operandi of Muting fancy wood, such as Is don« on desks, &c—

A Kl.eCttI.BEH.

[ i;05.]_ PASTF.HOARD,—I shall feel greatly obliged of some contributor could give me some information In pasteboard making. I have tried sercrul methods ot drying, but tl can't find out how to dry them

WHAT IS WANTED IN MODERN ART.-If tho Arts are to flourish among us, says John Ruekln in one of his Oxford lectures, we must recover for the mass of the nation three requisites which they at present want: 1. Wholcsomeness of food. We must no longer allow them to eat aud drink poison instead of food; everything provided for their daily sustenance must be good and pure, as well as plentiful, iü. Wuolesonieness and decency lu dress. It must be such as becomes their rank - serviceable and good, and, at the same time, becoiniug aud in good taste. 3 We must improve the lodging. All ecclesiastical architecture is developed for civil and domestic building and its highest achievement may be eaid to be a " glorified rool." Now. in this our modern architects are straugely at lault ; they seem hardly to know what to do with the roof. Roofs ought never to bo built of iron, but always of wood or stone. And we must remember that the little roofs must bo built before (he large ones. Wc must see that the poor have houses suited to them, built as strongly as possible, and daintily decorated.

A NEW PLANISPHERE,—Mr. John Love, Royal Bank, Greenock, read a paper on the 25th Inst, before the Roval Scottish Society of Arts on "A new planisphere for showing tho altitude and azimuth of the sun or star." The object of the contrivance, it appeared, was to facilitate the etudy of nautical astrouomy by illustrating mechanically the observer's relations to the path of a celestial body, and more especially to the suu's path ; and tho means employed for this purpose consisted of two stereographic proj ections of the soliere, ono of which was to Ho symmetrically upon the surface of the other, and to revolve upon over It on their common ceutro. Both projections were drawn on the plane of the meridian—the oneon an opaque disc, being a representation ot the sphere with reference to the lines of its motion and the divisions of its rime; and the other on a transparent disc, being a representation of the sphere with reference to its Unes of altitude and bearing. The arrangement showed the systems of circles which respectively belonged to those two aspects of the celestial sphere ; and ft was the intersections of the two systems, read through the transparency, which were to give the Intended information.

A PROCESS FOR RE-SHARPENING FILESM. Werdermann has exhibited a very interesting and economical process for this purpose, before the Société d'Encouragement of Paris. Well-worn files are first carefully cleaned with hot water and soda: they are then placed in connection with the positive pole of a battery, In a bath composed of 40 parts of sulphuric acid, so parts of nitric acid, and 1000 parts of water. The negative pole Is formed of a copper spiral вигroundlng the files, but not touching them; the coll terminates in a wire which rises towards tho surface. This arrangement is the result of practical expeilence, When the flies have been in the hath ten minutes, they are taken out, washed, and dried, when the whole of the hollows will be found to have been attacked In a very sensible manner, hut should the effect not be sufficient' they are replaced in the bath for tho same period as before. Sometimes two operations are necessary, but seldom more. The files, thus treated, are to all appearance like new ones, and are said to be good for 60 hours'work. M. Werdermann employes twelve medium Bunsen elemente lor bis batteries.

SILVER.—The tenacity of silver has been etudied by Matthiessen, aud can be state»! for comparison as follows :—Alloy of tin and copper, 1 ; gold, 3-е to 4-.Ч; copper, 4 3 ; silver. 7 2 ; platluunl, 72 ; iron, 13 ; steel, 31). It is so ductile that a grain of it, can be drawn out 4<>0ft., and it can be hammered into leaves so thin that it would require 10O.00O of them to make a pile an Inch in height. Its conductivity for heat is to copper in the ratio of 100 to "3»; and for electricity, as 1000 to 951. Cast silver expands, according to Calvert, between 0" aud 100* per cent., 0-0"l!)91; and its specific heat 1» 005701. Although silver conduot« heat remarkably well. It» power "f radiation is very smnll, so that a silver vessel retains the heat of a liquid contained In It longer than any other metal Pure silver. If highly heated iu oxygen, will absorb Ö-15 to 7+Г volumes of th:it «ras ; aud under tho same eircumstaoros, will take up 0-3 ■" to "ИГО volumes o( hydrogen, 0488 to 0.515 earbonic acid, and 0 12 carbonic oxide—iu property differing considerably fi ou» palladium.

MULBERRY LEAVES,—The Science and Art Department of the South Ken-ington Museum 1ms placed at the disposal ol the Silk Supply Association a room for the purpose ot rearing silkworms during the ensuing months of May and Juno. The Association being possessed of some very rate and valuable eggs, or "grain," imported by the Hon. Secretary from Siberia, Mantchouria. Szechucn, Sbang-tung. and other ploceswhere there exists no disease, will be enabled to demons trole, for the information of eericiculturists in this country and in the colonlee, the simple practicability of silk production. Tho subject Is one oí national Interest, aud, it is hoped, will stimulate our Colonies to turn their fntteutlon ;to silk cultivation. Fcraous interested ta silk culture at home or in the Colonies, may have the opportunity of studying the entire procese by application to the Hon. Secretary, 05, Morgate-street, E. C.

THE GUINEA AND THE POUND.—It is among the things geuerally known that the guinea obtaiued its name from the gold from which it was made having been brought from the Guinea coast by the Africau company of traders. The first notice of this gold was In 164°, during the Commonwealth of Englaud, when on the 14th of April of that year the Parliament referred to the Council of State a paper presented to the House concerning the coinage of gold bronght in a Bhip lately como from Ouiny tor the better ad vanelng of trade But It was lu the reign of Charles II. that the name was first given to this coin. It is among things not generally keow that when the guinea was orriglnally coined the intent ion was t > make it current as a twenty-shilling piece; hut from an error, or rather from a series of errors, iu calculating the exact proportions of the value of gold and silver, it never olrculatod for that value. Sir Isaac Newt in, in bis time, fixed the true value of the guluea, In relation to silver, at 20s. 8d , and by his advice the Crown proclaimed that for the future it should be carrent at 21s. A curious question arises out of the fact alluded to; how many millions of money has the Englisu public lost by the payment of a guinea whon a twenty-shil ling piece would have sufficed had the costly error never have been fallen into?

THE PRUSSIAN NEEDLE-GUN.—A contributor to the Allgemeine Militar-Zeitung writes :—" As you know, two Improved models of the needle-gun are ом trial, which both aim at increasing the rapidity of firing, with as little waste as possible. From fifteen to twenty shots may be fired by them in a minute, so that the apprehensions of those may be quieted who are alarmed as soon as they hear another army can load more quickly than ours. I and many others are inclined to shrug onr shoulders when we hear the nonsenso so current on this subject. All who have any experience know that two, or perhaps three, wellaimed shots are the most we can obtain from Infantry iu the field."

EXPANDING BRILLS.—The inning Journal reports that Mr. E. P. Gleason has invented u drill applicable to rock-boring purpose*. He proposes a drill whose cutting parts are attached toa bar by a joint, and formed with a round back taking against an incl in», so that as the drill is dropped or projected the cutter nets laterally, aud finally forms, bycoutiuual working, a chamber with an inclined top and bottom surfaue surrounding tho drill-hole. This chamber can be enlarged by successive cuts above or below the first chamber. The cutting ports are easily sharpened or replaced when worn ; aud by using two cutters, acting on opposite sides, one forms a means of re-actlon for the other, so that the drill-bar remains central, or . nearly so, In the drill-hole.

MUDDY WATER CLEARED BY ALUM.-A comparatively sinaU quantity of alum will clear muddy water. A piece a» small as a hickory nut, or even less, according to the impurity of the water, will precipitate the dirty colouring matter in a pailful of water. It haselmply to be dissolved, stirred, aud left to settle. This method is frequently adopted along the Missouri and Mississippi rivers. In the manufacture оГ lakes used in palptlug, the dissolved colourlug matter is precipitated by alum. All this rests upon tho peculiar property of alum to combtue, when In solution, with the most foreign particles in suspension or even solntion.

TORTABLE MOTIVE POWER.—A correspondent of Nature draws attention to an Important discovery made by on Atnerlcau, which bids lair to supply tun want of a portable motive for machinery. At the lost expedition of the American Institute, it seems, thero was shown an elliptic lockstitch sewing machine driven by an olectric englue small enough to fit into a common hatbox. A series of eight migúete are sot on the periphery of a circle, and around these revolves an armature of steel which is continuously propelled by the magnetic aotion, aud thus operates the machinery that moves the needle. Connection with this motor Ib had by mutins of a email slide withiu reach of tho operator, at whose will the current may be cut off entirely or tho steed of tho ueedlo graduated, as may be desired.

DR. ANGUS SMITH ON ТПК CHEMICAL EXAMINATION OF AIR.—Dr. Augue Smith read a very important paper at a meeting of the Association of Medical OfficeTM of Health hold last week. The subject, says the Medical Times ami [Omette, was the "Examination of Air." and the most striking feature was the announcement tint he had detected and measured tho nitrogenous orgaulc matter iu different kinds of air, and thnt between couutry air and the air of towns or of close rooms there was a most marked difference In this rc-peet. The process adopted by Dr. Smith was very novel and Ingenious. It consiste in Bhaklngup a small qtrautity of perfectly pure water with a measured volume of the air to bo examined, by which operation the organio impurity of the air is transferred to the water, wnieli is nlterwards analysed by the ammonia process invented by Wanklyn, Chapman, and Smith The authorol tie paper expressed great conti.letu-e iu the result» he had obtained, and said he would not sctuple to ask for tho demolition of all crowded courts in towns, the atmosphere of which presented tho characteristic signs of contaminated air.

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