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[1831.]—MOTION "F WA.TEU.-Thu amount of water passing through a 9* pipe 12ft long, 1ft. hcail, is 1(15,877 gallons per hour* — Maty.

[1831.]—MOTION OF WATER,—I think that " A Subscriber from the First." will iiutl the following table useful to him, which shows tho velocity per second, due to different heights or heads :—

Height—Feet Velocity—Feet.

1 8.

2 11-314

3 13 85,6

4 16

5 17-8S9

8 lU5uit

7 21 llili

8 22-017

(I ai-
lo 25298

Tho height being 1ft., the velocity through his pipe will be 8ft. per second ; therefore when the pipe is9in. In diameter, nrea being 83-flin., the discharge per second will be 6107-25 cubio inches.—Striboh.

[1859.]—MATCH MAKING.—Mr. Ch. Mertons, at Lessines (Belgium), patented three months ago in that country, his lately invented dipping machine for matchmaking— Raihond Staeb.

[1805.] — WHITE METAL BEARINGS. — When the chair is cast, have it hollowed so that it will hold the metal, fasten the chair in its place, put In the spindle packed up, put somo clay round the spindle to keep the metal from running out, pour to the centre of Bpindlo, cut off any projecting metal, lay some strips of cardboard on each side of the spindle, put on the top part of chair clay round the spindle as before, and pour through oil hole. This mode requires neither fitting nor boring. I have seen lead used alone, and wear very well.—Milly.

[1887.]—PUTTY.— Let " Hurtus" got about 201b. of whiting, and pound it up line, then add enough raw linseed oil to make It iuto a stiff uniform dough. I found it took three pintH, and that was not quite enough. Then hammer it well out, as thin as it will HO, and work It well till it comes soft enough. I was told that one pint of oil wns sufficient for 151b. whiting, but found three pints hardly enough. This is the best and cheapest putty. He had better add the oil as he wants It—not all at once, and warm the putty before a Are—Augustus.

[1889.]-BELGIAN AND FRENCH PERIODICALS.—No journal similar to our ENOLisn MeChanic is published In Belgium or France. In no one, such variety of instructive matter is to be found, as they respectively and for the mist relate to Borne special branch of science. If my fellow correspondent "Argente " will communicate with me through our Mechanic what subject he more especially preters, or what branch of science, mechanics, or technology, he wishes to be Informed on, I shall be glad if 1 can to answer his demand—Raimond Staes.

[1894] -CHINA GRASS DIVISA.-I have also been puzzled by tba; name, and never could get any conclusive Information about the plant; the following article appeared in several French reviews :— "Dr. Grothe, director of the manufacture of Kammelsberg. near Berlin, employs with great success, for making figured stuffs, much in demand for England, yam of China grass, white or dyed in different colours. He produces the China yrnss dieisa {sic) in a plantation he planted, and which yields 60 per cent, dry fibre, and 30 per cent, long and very line filaments. In the mountainous regions where the soil and the severe temperature form a serious obstacle to cultivation of flax, the Urticacea; in genera], and the China glass in particular, resist perfectly. (?) The 1'russian Alining Office Ids taken into serious consideration a culture which feems tofui ulsh an accessory and very precious resource to the miners oi the Harz and of Hanover." I made several inquiries, but always failed. I even wrote to Dr. Grothe, but did not receive any answer. If later 1 learn anything, I will communicate it to our English Mechanic 1 supposed also thnt divisa might he a fault of impression for dioiea, or for diversa, different kind.—Behnabdin.

[1895.]-C0WR1E COINS.—The following letter from Lord Alfred Churchill, to tho Secretary of State for the Colonics, which I extract from the " Technologist, of July, 1805, deals with this subject:—" The Council of the African Aid Society have had nnder their consideration the necessity and advantage of finding somo metallic substitute for the cowries, hitherto in uso among the natives. A currency ought to be adapted to all the wants nnd habits of the people for whose use it is intended. Cowries, as a circulating medium, have been for a long time In use in the countries of the Bight of Benin and the Niger territories. Since the annexation of Lagos to the British crown, all the English coins have been introduced there. They arc coming Into ufo among the natives, but do not suffice for the general wants of that portion of the community. The loweBt English coin In circulation is the farthing. The value of this is 30 cowries, but a great manv articles of daily consumption are purchased much below that price. Unless, therefore, some smaller coin be Introduced, cowries cannot he abolished or replaced as a clrculatingmedium. In the interests of progress and civilization, of which Lagos is an outpost, It is desirable that tho currency should be solely metallic. The Council of the African Aid Society have had an opportunity of seeing the small coins—one mil each—now being struck at Her Majesty's mint In Loudon, for Hong Kong Those coins being each one-twenticlh of a penny, or one-fifth of a farthing, would be the vnluc of six cowries. As nothing worthy of mention can be bought for a lower sum than six cowrie", those coiuB would respond to all the minor wants of the native Africans, while their being perforated, so ns to enable them to be strung as cowries are now Btruug, would render them equally safe and convenient as cowries, while they would not be more than one-seventh of the average weight of the smallest cowries used in the interior trade. The Council of the African Aid Society beg leave, therefore, to suggest to Her Majesty's Government that it would be advisable, and of general advantage, to introduce perforated coius of a similar size and value, in the I


currency of Lagos, Cape Coast, Ac. The Council also beg leave to suggest that the perforation, in a similar maun. r. of other cuius iuiendod for circulation iu native Western Africa, would tend greatly to facilitate their nsu aud favour among the people." I send a sketch of the "mil" above mentioned; this may, perhaps, Interest soma reader. White cowries (cypiasa moneta), are extensively Imported in Western Africa from India; Hamburg firms, established at Zanzibar, send away blue cowries, whichseem to yield a great profit. A hole is made in the shells, and they are strung on threads of rulm fibre ; 40 shells = 1 string. Many merchants in Lagos occupy eight or ten girls stringing cowries. 2000 blue African cowries weigh 80 or 901b., the white Indian ones 35 to 401b.; 200t> = about it dollar.—Bernardin.

[1898.]—EQUATION-In the last number of your paper, page 640, C. II. W. Biggs announces his Intention " In a short time to commence" his " Notes on Algebra." Permit me to express a hope that "C. H. W. Biggs will first master the question before undertaking to teach others, otherwise those readers of the English Mechanic who put their trust in his "Notes," will be in danger of falling into errors, as, for example, that the square of — s/5a; + 10 Is — 5x - 10; or that

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See reply by C. H. W. Biggs to ri896] Equation, page 615. The reply by "Hugo" to same Equation, same page Is quite correct. -senior Op.

;i89fl.]—EQUATION.—If Mr. Biggs will consult Wood's Algebra, he will find ln;the chapter upon Quadratic Equation, page 118, tbe equation fully discussed In Its unaltered form: x + Jbx + 10 = 8.—H. C. C.

[1910.]—TURKEY STONE.—I cut a lump of turkey stone Into twelve oil stones when I was an apprentice, partly with a sheet of copper, and partly with a sheet of load, of course (IttPd to wood frame for convenience, in both cases with sand and water, but I cannot remember which cut it quickest.—Jack Plane.

[19l3.]-GAS BURNERS to burn common coal gas are not of much use to Illuminate dissolving view apparatus. I have tried several, including a 60-hole argand, but always found camphorated colza oil more effective. My experience led me to adopt the improved oxyhydrogen burner when I want more light than oil will give ; the apparatus is very simple and quite safe. —C. Ward.

[1929.]—LACQUERING—In answer to "Inquirer,"

1 beg to send him tbe following method for lacquering brass-work. If he is going to proceed on old wotk he must first boil tbe articles in strong soda ami water, Bo as to get off the dirt and old lacquer; then scrub them with sand and rinse them. The next process Is the dipping, for which bo will require an earthenwaro pan capable of holding the articles, which he must fill with aquafortis, which he can obtain at any chemist's;

2 pails of clean water and a box of sawdust. If be has any means of keeping tbe sawdust hot all the better, and a nice clean brush. Now he will have to proceed as follows :—Tie the articles on copper wire, dip them in the acid, then rinse In the wster and well rub them la the sawdust till thoroughly dry, and then brush the sawdust off. If there are any parts that want relieving this must he done with a bright steel burnisher and a drop of stale beer, then the articles arc ready for lacquering ; but If the articles have tarnished, to restore their brightness he must dip them again, but he must dilute the acid with ten times its weight of water, rinse and dry as before. Now tor lacquering them he wHl want something to beat them on; a plate of iron with a gas-burner under it will db; but If he has an oven that will do as well. If he wants that red gold tint on his articles. It is best to get French gold lacquer and mix a drop of red lacquer with it; he must heat the articles so that he can just bear the hand on them, and then with n soft camel-hair brush lay the lacquer lightly on, care being taken not to lay it on too thick or to get the articles too hot. If there 1b anything else that" Inquirer" wants to know, 1 shall be happy to inform him.— W. Ssabrook.

[1931.]—LINCOLNSHIRE IRON.-I beg to inform "R. W. M," thnt the ironstone of this district contains In Its raw state from 30 to ."5 per cent, of iron of a very good quality. The average price for the ore in wnggons at the mines is from 4s. 9d. to 5s. 3d. per ton* and 5s. 3d. to 5s. 9d. per ton delivered at the nearest wharf. Should " R. W. M." require further Information, I 6hall be glad to help him.—Blast Furnace Engineer, Frodlnghnm.

[1934.]—LOGARITHMS. - To "Y. P. W."— Chambers' "Tables of Logarithms," contains seven figure Ubles.of logs., log. slues, cosines, Ac, and natural siiies and cosines, with a heap of other information; proper title "Mathematical Tables," gives a few' examples at commeiiomeut to explain the tables, has no treatise. Can be had anywhere for 3s.—Maty.

[1054.J-CEMENT FOR PARAFFIN LAMP-Let "Noodle" get twopennyworth of shellac and melt It by the firoin a tin cup, to which he may add a small drop of keep the shellac from burning. Whea melted he then may fill the brass socket aud slick in his reservoir; he will fiud ho has a good job.—Ling Fl9H.

[l'J(il.]-CAT!PENTERS' PRICES.-I have put up fencing of four railings and one stake post: have morticed the post aud pointed ttio railing* for Gd. iter length, but thoy were lort. long, that however is immaterial. The posts and rails had to be put up. but if put up at per chain it would make a considerable difteronce ; they were laid out ou the work ready lor use gratis.- Usleakmd Platelayer.

[1904,]—CARPENTERS* PRICES.—Posts, 12s. per 100 for mortising; Id. per pane of 4 mils for chopping

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From (7) and (8) by transposing and dividing-,
o - c a' + &» - <■ (a + 6) - (6 — c) *

e - b a* + c* - b (a + c) - (o - b) z'

whence, by multiplying up and reducing,

z(o5 + 6' + C-ao-tc-cao = a3+o>- <?J — 2 n'

c + 2a<l>-2b>c + 2bc'>-Abc

whence dividing each side by the co-effir/ene of » ft will be found that z = a + b - e. I should be g.'.d' to see a neater solution from some abler pen than mine —Sesiob Op.

CIMO.]-MOULDING MACHINE—If "Jonath" would visit any of tho undermentioned plices ho would see moulding machines at work. To *s one for half an hour will give him more knowledge iiVn..a "R1,*..10 hi» query. Houldwortu'B, QtittvliirlSuM T01?hs'S; Howard's, Bedford; fVwry' Enfield Lock; Royal Arsenal, Woolwich. It dm places are inaccessible to him, I shall be happy to afford him full details in the English Mechanic.

T^i.9?0.1.- 7ARNISH FOR IRON PATTERNS. The following is WUat I have seen used with success In several foundries In Glasgow; It is better than Deeswax :—When tho pattern comes from the finishing shop smear It all over with oil rubbed on with a bit ^ iWa-MCi p"Ut in tbe drying stove all night, so as the oil will burn in; if not in a hurry for tbe pattern repeat the dose. I can recommend this, having seen It done and having dono it myself pretty often.—N. L. „ t19TM-]—MQUID GMJE.-I have mads a strongliquid glue by treating Russian glue with a littlestrong acetic acid; add a small quantity to tbe powdered glue, cork tight, aud let It stand for some hours; you will find It soften; by adding more acid you can make it of the consistency you require it. A common recipe for ordinary liquid glue, and which I nave used, consists of 8oz. best glue, dissolve iu Jpt. water, add 2,oz. nitric acid; cork up tight.-J. Chebry.

[1981 ]-ENAMEL.-If Mr. Walker will try tbe following, I think he will find one or both answer his purpose :-No. 1. Oxide of tin 8, flint 3, b. rax I. No. i. Oxide of zinc 2, Cornish stone 8, whltlajrl.-forA. [19850-SIDE LEVER ENGINE— I bee to Inform

SulTold Amateur" that the aide lew engine was that which used to be almost entirely »*d for marine purposes. I think it was Invented by J«mes Watt, but I do not know if he patented it. The principle otttds engine Is similar to a beam engine, only the beams are down at the sides (of the engine,) sua tne>' are connected with the piston by means of a cross head and connecting rods. The other end of the beams or side levers is connected with the crank. The advantage of this kind of engine is that all the moving parts ar» balanced by each other. Tbe connecting rod from the beam to tbe crank Is very long, therefore motion is transmitted to the crank very equally aud with very little strain. The heaviest parts of the engine are brought very low down in the boat Tiio disadvantages are that It occupies a very large space, it is very heavy, very costly, and not applicable to screw bouts. —H. Chapman.

[1087.]—WHAT 18 IT?-It if B pedometer for counting the number of steps In walking, not mush Id use now. Time tells the distance travelled over, tor the walking rate Is nearly uniform forencb Individual, and is soon ascertained by counting a few mile stones ouce or twice.—H. W. Reveley, Reading.

ri«87.}—WHAT IS IT?—1 believe the instrument "Querist" has rot hold of Is a pedometer, which is worn in tbe waistcoat or other pocket, and measures, the distance walked. Each step taken causing a vibration of the weight, which acts In one of the toothed wheels.—Iota.

[1989.]—NUMBERING BOOKS. — A bookbinder would stamp the books In gold for a very small charge, or the numbers might be painted on the backs in oil colours, black figures on a white ground.—Iota.

[19S9.]-NUMBERrNG BOOKS.—Gum tbe Lack oi your paper, write your title numbers, Ac, in good ttw, but blot immediately with blotting paper; afew hour* after size with common size or gluo water, let this thoroughly dry. nnd then varnish with pale copal, cut up, and stick on in the ordinary manner. Of course wo suppose a sheet or a few sheets to be rone at the same time to be worth this amount of trouble, but when dono this mny be termed everlasting—S. T.

[1990.]—METALLURGY. — Tho most recent and complete work ou this subject is that by Dr. Percy. It is published by J. Murray, price 21s.—Bf.ta.

[19«1 ]—CANVAS CANOE.— I would persuade our friend against milking his eanoe of canvas on ribs; it is impossible to obtain good lines, or in 1«» technical words, no curve cau be obtained; tho outline boat would consist of straight lines as nearly approaching tho curves necessary as is posilile in lessening the distance of the point of attachment to the frame, but the result is in the highest degree unsatisfactory.—S. T.

[1901.]—CANVAS CANOE.—After laying down tbo keel and fixing stem and stern-post, let " S. F." make

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[4005. l-RAZORPA3TE.-Crocusandtallow,mixed with pestle and mortar. Obtain ut a watchmaker s tool warehouse— S. T.

[10050-RAZOK PASTE.-In reply to •• Dundreary r can safely recommend the following :-Reduce emery t, an impalpable powder, and sift through Hue gauze io catch any large particle; mix the powder with a. much spermaceti ointment as will form a thick paste, audlay on the strap— Gitcue M Anito.

[2005.T-PASTE FOR RAZOR STROPS is thus made :-Oxide of tin, levigated loz.. saturated solution of oxalic acid sufficient to form a paste. 1 his composition is to be rubbed over the strop, and when dr> a little wnter may be added Oxalic acid having a great affluitv for Iron, a little friction with the above pow dcr will give a fine edge to any raior.— 1 Autau.

r200fil-TO CLEAN STEEL ORNAMENTS. "Young Wife" may clean them by rubbing them over with some fine emery and oil to go. off the rust mid then removing allthe traces of oil and emery. rub them with a clean brush with some crocus ami w»«w; lastly, polish off with a little dry crocus-thls irfflTitaj.thMB if they arc not very rusty •, but If they arc it will be impossible to do anything with them.—A. A. A. [4007.1 -TEMPERING DRILLS.-IIeat your drill oa.lull red, allow It to cool slowly then rub thy

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Let Rand S Jc

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"r on a\rSt'orweY grindstone; now lav the point i vour drill on a lump of Iron previously heated red h-. and the moment your drill has attainedth«! colour W,m require, dip and stir it in cold water (or oil, If a .mall tool). The gradations of temper iire -mild, blue, hard, dark straw, very hard, pale straw.-S. T

[2007 1- TEMPERING DRILLS-Heat the drill II li^ no from the point until it become, blood-red; nen dip it in water about an inch, hold It to the light, and you will see a blue tint, which gradually descends, and vXnit 1. about l-16th of the point slack it


ram.!- Con Tents Of Iron Pans.-to find

the o7b c content, of iron pans with circular or rather spherical bottoms, you must ealculuto the body ot the pan and the bX/dUtinctly. The body of the pan fs a evlinder ■ to measure It multiply the square of the dUmUerby-rsM.and the product will be ho area ol fee bsse; multiply the area of the ba» bythe.height nnd the product will be the solidity. If the bottom is nTf of aP»phere, multiply the cube of Ito *£%«[.£ <MM and divide by 2 ; the quotient w 1 ^tl.e.olidi > If the bottom is the segment of a sphere to I times no smmrc of the radius of the base of the segment RddX«uarc of It. height; multiply the sum by the Se gh ana the product by -SUM for lb<■ .olbdlty , add the solidity of the cylinder to that ol the bottom for

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tlie total contents. If the measurements .re takeu »nd calculated In iuches. divide by 277-474 (cubic inches in 1 gall.); the quotient will be the

contents in galls. If in feet.

multiply byOJJcubicg.Us. in

lft. nearly), the product will

be also galls. Example—

A circular pan 14ft. diameter, height of body 8ft..

height of the bottom, being a segment of a sphere, 4ft,

J2 X 12 X Wrt x 0 = 678-58Wft.

0x6x3(+4)x2x -5530 = 1174864

Cubic contents in feet .

in gals ..

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Do. da Jennings

[2003.]—WHEEL CU ITING.—In answer to " Burslem," special machinery seems Indispensable for a speclsl job, and it is absurd to rig up au apparatus for a few wheel, whon you can get them cut for you for a trifle. What you must have for the purpose is a division plate, containing all the numbers you want, and a cutter framo to carry the cutter, on a vertical spindle. I have seen patterns cut, or rather plaued out of white metal In a lathe by means of a single point tool of proper form held horizontally—J. K. P.

[20121—MULTITUBULAR BOILER.—The way in which the tubes are fixed Into multitubular boilers. Is a. follows:— They arc put loosely in first, and whilst in their place a conical plug of steel is driven into the ends so as to open them a little, nnd so fasten them into the tube olaUs. If they arc not perfectly watertight they have to be caulked a llttlo to make them Bo, —H. Chapman.

[4041.]— MAGIC LANTERN— Inanswerto"George," I would say he will get as much practical information on the construction of magic lanterns In the back numbers of tho English Mechanic (Vol. VI., paues 3'J.">, 444,441, &c, &c.l as any work on the subject that I know of. A. to J-plato photograph lens being suitable for a magic lantern, I know by experience that thcro is no lens more so If a long range Is required with a4lln. condenser. The lantern requires to be 45ft. dl.tnnt to cover an 18ft. screen, and will give a clear nnd distinct picture with oxy-hydrogen light. A }-plate lens will give the same siic picture at about 28ft. distant. Condensers for magic lanterns are of various forms.No. 1 plano-convex, No. 4 plano-convex and double convex, No. 3 two planoconvex, which I think gives the best results. No. 1 being only used for the common construction of lanterns. Distnncc between condenser nnd front lens is &4ia Condensing lenses may be had mounted almost from nny optician. The price of'a4Siu. is £2 2s.; 3}in., 18s.-J. V.. V., Edinburgh.

[4021]-MAGIC LANTERN—The price of double condensers 3Jin. brass cells is from 14s. to l<s. Any optician will supply them, but Cox, of 56 .Ludentuhill, or Pumplirys, of Hiimlngham, may be rolled on for quality and pTlae. I have seen a J-plato portrait lens used with good effect, but " Uucrnsoy " writes from personal experience, thereforewkh authority on the subject. "The Magic Lantern, aud How to Use


i. done in klers of wood or iron heated by steam, ffhe 1st require, about 4 to Bcwt. of lime made iuto thick cream, aud freely .prlukled amongst the waste as it is thrown in the kicr. The washing requires plenty of water and is done in ordinary dash wheels. After being w.Bhed the waste Is Bteeped iu a solution ot muriatic acid In water (4 to 3 per cent, of acid) then drained and sweetened by placing under a shower bath using plenty of clean water. The 4nd bowking is done with soda ash, and takes from 3 to 5cwt. ol ash per ton of waste. The drying Is generally commenced In an hydro-extractor, nu.1 then finished in a stove or the open air. which is preferable. If «3° desires further information I shall be happy to give it to him.—Feu Follet

[2042 1—VENEERING.— Soak yonr glue until It rrelatiuises in old water, carefully boll In proper gluenot warm your veneer; all the rest depends on three points of detail- cleanliness, close contact of the Surfaces, and the expression of all excess of the glue -i.e as small a quantity really between the Burlaces o be united as Is prsctlcable.—B.T.

ftfrn ]-AM ALGAM—Kill some mercury with pure fin foil; when It has lost Its quickness apply with small quantity only of clean tallow.—8. T.

[40211-AMALGAM.-Mix your amalgam with as much lard as will mnko a thick paste and spread it on the cushions with a knife.-gitche Maxito.

[20*31—AMALGAM.—"T. O'Connor" will find tho following useful :-Melt together 3m. of tin, Sox. of ziuc an<f Ooz. of mercury; when cold, powder ana mix with 4oz. of lard, and lox of bees-wax.—Beta.

r*0Ul- MENDING GUTTA PERCIIA.- Doe. J i.a'u'd mean an india-rubber ball ?-lf Bo, wo can tell him how to repair it. A gutta percha ball soems to present no difficulty. A patch could be hua ed and put on, unless, indeed, the ball be very ok: then tho material will b! found perished, and very difficult to deal witb.-S. T.

f2020.]-PHYSIOGNOMY.-Lavoter [» the best authority. There are cheap aud dear edition, of his work.—Briefless Barrister.

[40*J]-STAMPING IN COLOURS.-Presses for this work mav be bought by auy one. and with practice any mav do it. A prepared gummy Ink is spread on a steel die in which the dovic- is sunk ; the surface is then wiped clean with the ball of the thumb, leaving the ink in the device. The paper to bo stamped is placed on the die and a leather " matrix is brought down on to it by moans of the press, and is by it forced iuto the cuts, the ink ndheriug to the paper forms a coloured Impression In relief. This process is caUed •' relief " .tamping.—Iota.

[2038.1—8US DIAL—" T. S. H." to ".Tuplter. — The hour angles for a horizontal suu-dial In latitude 5«°, beginning at the 14 o'clock line, and reckoning eastWuru and wostward. are U° 20-, 25° 15', S9° 14', 51°

45' 71° 50' 90° 'T S IT

[4012 i-CLERK OF WORKS.-A clerk of works is a man placed on the bulldiug by tho architect to watch the Interests of the proprietor. He must be "•<•''<»<:nuainted with all kinds of building materials and thofoiK'lily understand where and how each article ought to be used, whether wood, Iron, brick or, and has power to allow or reject anything he consider.not according to contract.-jack Plane.

[S0421-DUTIESOF CLERK OF WORKS—I think •• Aspiring Mason " will find the following the duties of a clerk of works :-He will have to look after the workmen, see the work is properly finished, point out to the nr.hitect any Improvements he may thinx nt, make op bi# weekly report, and send to the architect, drawnijst of the w:orking drawings, and measure up all extra work; In fact, ho is nothing more than ttie superintendent of the work in the absence of the architect—Delta.

[2043.]-FILLS — "'Wry Face" finds it a difficult matter to take pills in the ordinary way. Nothing is better than an oyster; it is a capital thing to carry a pill to toe stomach Use it in this, way:—Slit the tliick part of o native oyster and put in the pill, then swallow the whole. Children who are fond of oysters, and who cannot be made to swallow pil *, may be thus effectually deceived. Another mode of taking- offensive pill-*, or nauseous medicines, is to prepare the mouth beforehand by seme aromatic substance; for instance, chew a clove or a piece of orange peel or lemon p*el, or in lieu of this first put Into tile mouth a bit of alum.—Tactap.

[2043.]—PILLS—In reply to " Wry Face," there are several plans for rendering pills tasteless. Some of these plan* aro patented, some not. The principle aimed at in all la to cover the pill with a film which shall resist the action of the saliva during the short time that the pill is In tho mouth, but that Bhall bo removed in the stomach. This lilm may be either metal, as gold or silver leaf, or a varnish composed of balsam of tolu, or some similar substance dissolved inspirit, or a costin^composedof mucilage of tragacanlh and sugar. I have repeatedly been told that coated pill* have passed through the whole length of the intestinal tube, and have "been pnssed unaltered through the system Under these circumstances I leave your correspondent to Judge what good they had done. A plan which I myself have found very efflcociom Is to screw each pill tightly up In line tissue paper or cigarette paper, cutting off the superfluous material. A similar plan Is adopted with balls for dogs and horses Tho English Mechanic improves, and I am glad to see the quotation from " Montaigne" restored to the head of the Correspondence columuB. —Arthur W. Blacklock, Newbridge, Uardgate, Aberdeen.

[2043 ] — PILLS. — Fir=t see that your pills are thoroughly dried, then stick each with a pin the head of which is bent down liko a pot-hook f ; now dip the pills one at a time in a strong solution of gum arable and hang on a string to dry in a warm place. This will not only render the pills tasteless, but prevent the deliquescence some kinds arc subject to.—8. T.

[2043.J-PILLS.—If " Wry Face " will apply to any chemist, he will Hnd that his grievance can be remedied without much trouble or expense.—Heta.

[2046 ]-GYMNA-*TIC.S.—The following works are recommended:—" Gymnastics." by Chiosso, price Is. 6d., Walton and Maberley; "Course of Gymnastic Exercises." by Holland, price Ss. Oil., Oliver and Boyd; "Roth's Movements or Exercises," price Is.; " Ling's Gymnastics," by Roth, price 3a. Cd., Groombridg?.— Beta.

[2049.]-LANTERN LENS.-A single plano-convex Jena would do, but the result would not satisfy you. Many cheap lanterns are nearly useless on this account; go to a little more expense to purchase a double condenser, or If you have a good flint planoconvex, get an optician to adjust another to it. Write to Cox, of Ludgate-hill, or any practical optician.— C. Ward. *

[2049.]-LANTERN LENS.-If " Lime Light wishes to have good results from his magic lantern, I would recommend him to use the double combination 3jln. oondenaer.—J. E. V., Edinburgh.

[2053.]—BEECII.—Expose the wood to (he presence of steam in a oovered vessel for a few hours, then withdraw it and allow it to dry slowly. It should be under pressure of some degree, even if not moro than 1 or 21b. to the inch.—S. T.

[2054.]—HYPOCHLORIC ACID.—Such an acid has not yet been discovered. The only oxygen acids of chlorine are:—Hynochlorous acid, HCIO; chlorous acid, HCIO,; chlorlo acid, HCIO,: and perchloric acid, HC10.,.-KnNE8T.

[2055.1-CO1N.—The piece, as per engraving, la a weight of the double crown of James 1st There are others of various weights according to the denomination of the gold coin, the unit 22s.. the crown 5s. 6d the thistle crown 4s. 4id., the half-crown 2s. 9d. I have standard weights of all tho above, as also those issued in 1018. The wcightswereissued by Royal proclamation from the Royal mint, nrd the chief officers in all cities, boroughs, and town corporate of England and Wales were commanded to provide such weights and scales as provided by the master of the mint, and all persons were forbidden to have or use any other weights for the gold coins. Vide Kuding'a '• Annals of tho Coinage," page 374.—D. T. Batty, 0, Feunellatreet, Manchester.

[2054J-TJOIN OR COUNTER -In answer to Mr. Smith, the engraving represents a card counter. I nave a similar one in my possession, with Vs. VIn., instead of XIs. English coins were made of tin and copper, and now are of branze, but brats ones were never struck.—HeNry W. Henfrey, M.N.S., Markham-bouse, Brighton.

[2057.]—ZINC PLANT.—Form a feeble solution of acetate of lead, suspend In It a piece of zinc and some brass wires, tho latter represent the branches of the tree.—Ernest.

[2057.]-ZINC PLANT.-The zinc plant can bo made by "A Late Subscriber, K. S." by twisting a piece of wire round a lump of zinc and inserting one end In the cork of the bottle; then attach other plecea of wire to the zinc and twist them in any form he may think proper; some put a little chins doll in between, and beads of various colourB, which has a curious effect; then fill the bottle up with water so as to cover the zinc, and put a little sugar of lead in, and lot it stand perfectly still; the tree will begin to grow. A pennyworth of sugar of lead may be obtained at any chemist's—enough for 3 or 4; It will cause a white cloud, which clears off.—A. A. A.

[2057.]-ZINC PLANT.-Thia la easily prepared by suspending a piece of granulated zinc in a strong solution of acetate of lead. In a short time beautiful plates of lead will form upon the zinc, and increaae till the solution becomes exhausted.—Beta,

[2057]-ZINC PLANT.—"A Late Subscriber,E. S," Is mistaken In supposing that it Is merely water in the bottles in which zinc trees are made. It is a solution of acetate (sugar) of lead, in water that is used for that purpose. Apiece of copper wire is attached to the cork of the bottle long enough to reach to the liottom, and if you want branches to your tree put pieces of wire across, you Anally fasten a small lump of zinc on to the top part of the wire, take care that it Is im racrsed In the solution, c-irk up your bottle, and in a few days yuur tree will bo comple;e.—Iienhy ChapMan.

(2 50 ]—AQUARIUM.—Tho great bugbear in aquarium manufacture consists In having a rabbet for the glass Instead of a groove, the former entailing trouble and vexation without end. Take, then, a groove, and make the putty of red lead and copal varnish ; In a few days all is hard, sound, and iusoluhle The putty must bo usud as made, as it sets very quickly.—S. T.

[2039]-CEMENT FOR AQUARIUM.-I have kept fish of uiany kinds in my aquarium for years: it is put together with red lead putty, commou putty is useless. Red lend putty is red lead (In powder) worked up well with white lead (in oil) as stiff aa it can be conveniently used-, leave it a few days to harden.—Jack Plane.

[20G3.]-MEASUR1XGTIMRER.—Sumerous works have been published on "Measuring Timber," but generally speaking one work is as good as another. Of course everyone will recommend his own or the one which he has been most accustomed to use. I have been for sometimo in the timber trade, and find that Aitkin's tables arc as good as anybody's. Cost I think 4a. 6d.—Gitciie Manito.

[2003]-MEASURING TIMBER.-R. Livingstone should obtain "Hoppus's Measurer," price about 2s, It may be obtained at a second-handbook shop for considerably less.—JflNATII.

[WKMO-QUESTION OX LIGHT.-Tho numbers of vibrations per secoud, of the mean rays of the several colours of tho spectrum are. In millions of millions —Red 497, orantre 528, yellow 52U, green 6t)l, blue 018, Indigo 6SG, violet 72s.—Ernest.

[2066J-ZINC PLATE FOR BATTERY.-To amalgamate zinc plates, clean thoroughly with diluted muriatic acid; pour tho mercury on, aud spread it over with a brush; allow them to drip, and they will be rendy lor use. Tho best sheet zluc of the requisite thickness nnswera the purpose aa well aa any other kind-J. E. V., Edinburgh.

[•-iOnfl.l-ZINC PLATE FOR BATTERY.-Tlad | "G. Deku " put in praotice the slight k-nowledge he i seems to be in possesalnn of in regard to his query, he would have found the practical part of it so easily acquired as hardly to need troubling the Mechanic for Information upon eo simple a matter. The ordinary commercial sheet zinc will do, procurable from any metal warehouse. After acourlDg the plate clean in the a-*ld solution with a piece oi rag or a brush, pour upon It a little mercury, and by still continuing the rubbing " G. Deku " will find the mercury spread itself evenly over either Bide of the plate, making the amalgamation of the plate, if a matter of question, one of very little difficulty Indeed.—II.

[2068.1-TO AMALGAMATE ZINC PLATE FOR BATTERY.—G. Deku can make the mercury flow over his plate by adding a little af the pure acid and then rubbing Itoverwith a piece of tow or waste cotton, then well washing it in plenty of water. If he cannot get on, will he write to our Enulisu Mechanic r— A. A. A.

[2068.]-CONTENTS OF IRON PANS —To find


this, multiply the square of half the diameter by

113 and by the height. For instance, the first pan contains: 11 x 11 x 3*5 x 11

58-Cin. = =

2 X 2 x 113 x 2 522 cub ft. 118 cnb. in. To mcasurethe eubic contents of a globe, multiply the cube of the diameter by 0 5236. —ernest.

[2068]-CONTENTS OF IRON PANS.—To find the solidity of a sphere or globe multiply the cube of the diameter of the sphere by -5236, and the product will be the solidity. To find ihe solidity of the segment of a sphere.—To three times the square of the radius of the baBe of the segment, add the square ef the height, and this sum multiplied by the height and 5236 wiil give tho solidity.—Jonaih.

[2008.]—CONTENTS OF IRON PANS.—The contents of a pan in the shape of the annexed sketch, can bn found as follows:—To three times the square of tho radius C F. add the square of the depth F G; aud this sum multiplied by the depth F G, and the product again by 5236, will give the solidity of the bottom; and the product of the diameters A B and C D, added to the sum of their square s; and this sum being multiplied by the depth E F and again by -2618, will give -lhc solidity of A B C D, which, added to the solidity of the bottom, will give the contents of the pan tequired. To find the cubic contents of a globe multiply the cube of the diameter by '5236, or the cube of the circumference by 016887.—J. Likton.

[2069.]— PHOTOGRAPHY'.—In reply to "Lex," there is no stated amount of alcohol used for the purpose he speaks of—merely a few drops or so; but I should advise him not to use it at all. With some samples of paper I have found that It tenda to blister the paper, whilst with others I believe It almost prevents it. In no case, however, should I advise methylated spirit. That is best out of the operating room altogether, either the spirit of wine or the other, both being impure. My method of w rklngis to pour back the solution (after sensitising) Into the bottle wherein is some kaolin, and the next time that 1 want to use It

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I shake it well, and then filter. nfterwarclB adding* little bit of nit. sllv. to replenish waste from kaolin, anil filter. I have sometimes, especially afu-r a»i»« a lot of paper, seen the bath nearly black, bat the above entirely removes it.—Mi's.

[2070.J-STENCIL PLATES.—Ones onr friend ■• Tbe Vicar "'adopt the plan of cutting his stencil |>l»tes> out of thick foil (an alloy of lead and tin).' 1 r to. irmt freedom may lie gained even in the repi-tition t>f the same design by departing from the strict pwmetrieal lines. In cutting a frcih stencil plate even frwm tbe old pattern, on apparently accidental deviating may be exaggerated to give greater ease. 3I*M5Chromatype has be>-s used f >r the purpose named in I.tijade, but there is none of the richness of colour nbtamaMa bv Bteucil colouring as to decalcomanic tran*firr» *r» obtainable at shops In Oxford-street on either -idee* the Rege-it-ctrcus; but the writer has ne»er seen any sutject suitable for the purpose named.—S. T.

[207i] — PITCH. — Shoemaker's wsx S» made by melting together about equal quantities of common black pitch and rosin. When thoroughly melted, a small qusntltv of a common oil Is added, to soften the compound. The quintltyof oil dependson the smoo of the year, more in cold and less In hot weather. To make it lighter In colour It Is drawn out by tbo hands. An article called prepared pitch Is now sold by the trade; It merely requires to be melted, and the oii added.-CRtSPiN.

[2073.]—CEMENT FOR PARAFFIN LAMP.—I have one In dally use that was repaired seme mnntha ago with white lead. The white lead must fcegrox*— i. e., free from baryta, its commonadulteram. sad tbe lamp must be laid aside for at least u west or two. —s. T.

[2075.]-WATER-PIPE SWEATING.- Tki rapposed sweating is a condensation of v a poor « atmospheric moisture on the surface of the pipe Item the lower temperature of the water contained tkerein. —S. T.

[2079.]-VARLEY'S PATENT COIL.-Herewith 1 send you diagram of Varley'spatent coils used ia fen Office Instruments. It is same size aa the coll itself. Ihe only difference In tbla coll Is the needle and the two permanent bar magnets, which stop the injurlouj effects oi lightning upon the coll. It works exceeding well, muchquicker than the old system. If H. R. H" wishes, I will send him a diagram of contact keys used in these instruments. A'A'permanvnt bar magnets, 11 needle which has north and south poles as marked, C C'colls, D pinion of needle.—« . Goldino.

[2©81.]-PnOSPHOR\JS.-If "M. P. S." will look at my recipe for phosphorus paste In No. 257, page 588 [1750Vhe will see that the phosphorus does not require powdering. The proof spiilt will do that quite sufficiently— Gitche Manito.

[2081 ]-PHOSPHORUS. - If "M. P. s".iB''TMduce. Into a florence flask lpt. Ph°6Ph0TM TM*M?P',:" of rectified spirit, and heats In hot *»«« nnt" ?."; phosphorus has melted and then (ln.ertl.ig a weiStting cork) agitates briskly till cold he will Anthe phosphorus, on pouring oft the S. V. It., •""""" > fine for " paste." See Beasley, p. 393, for an excellent, un/ermenfi'nff paste.—A. P. S.

(20841- GRANITIC PAINT. —The menstruum employed for the granitic paint is silicate of pot..». which Is supposed to harden the pigment wUhwlucli It is admlxeVt and combine th,m In a durable manner, neither of which points arc, so far aa my experwMB goes, successfully attained.—S.T.

[2097.1-STAINING WOOD.-F. Drop probably Me not given his work coats enough of ;tain to overcome the blue colour he speaks of. If the stain is made properly, this is the reason of its not being Maes enough; he must do it several times, until tbe Woe colouris overcome. If this does not succeed, I «'« give him, through our Mechanic, a recipe that vm answer on his requiring it.—Gilder.

[2097.]- STAINING WOOD-Drop a lHtfc »" phuric acid into a small quantity of water, bTM*0**. the wood and hold to the fire ; this will PTM*«* » line black, whioh will receive a good polish. Or u« lpt. of vinegar, loz. of dry lamp-black. Boz of Iron rust sifted; mix and let it stand for a week Lay 3 or 4 coats of this on hot, and then rub with linseed oil and you will have averydeep black.—Minnehaha.

[2097.]-STAINING YVOOD.-I think if F. Drop were to give the wood a strong solution ol salts oi tartar before applying the copperas, it would verr probably die black. This process Is effective wit* leather, and might be so with wood. I think It ■ worth the trial.—An Initio.

[2102.]—VALVE.—I have used the annexed for a

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r2l36.1-I>IVlDlNG PLATE.-In answer to

tale." « 7°ur Pl»t«l»« 1»tne Pd11bt- and y,?u J"iT?
room for only, say «lx rows of hole., you will whet I
f*° f,n mine, rix.. S*\ V'8,100, 96, 84, 24 (the last for
Sard usage to save the others), as good numbers as you
"!„ Y,»t?. If yon want to do ornamental work by the
- double counting" of Captain Ash, then you must
nave 1M instead of 96. If you want large strong holes
andrsnnotfetln 360, then 240, 192. 140. 135, 100, 72,
are useful number.. That was the last I made. Be-
fore tbat. I made one for my own use of 300 outside,
then 11 13, 14,17,19. all in one row. with 216,140, 96,
*4 inside of that. If your plate is flat from ou tslde to
centre von can get in many more in the diameter you
mention, and I consider one of 13 rows, that I once
mads, complete enough for mo»t practical purposes.
Thenoe of the cutting engine, figured this week, has
37 row. containing every number up to 100 ana
ranging a. high aa 360. Good gunmetal is much bet-
ter Aan bras?. I get mine at Boweu's, Dorrlngton-
.treet. Coldbath-square Ask for best gunmet.ll
have .prions thought, of taking the gunmetal pulley
off my lathe, and putting on a cast-iron one, as the |
holea will last better. Division pegs, or "Index
vices " are, in my opinion, always made wrong. l»o to
Wilkinson, by all means, if you want something tirst-
■class, without being ruined. It la a chance if it did
not come to him at last, If you took it anywhere else
<o get it done. Say your outside row li Jin. from

•edge, and distance between rows — and state number

B 32,

•of rows you want, and direct to me at Pitcairn's, Library, Xing'!) College-road, N.W., and I will write out a list for you.—J. K. P.

r2l37.J—PITCH PINE WOOD.—" Pinastor" had better get tome of Stephens' wood stains. The cause of the wood looking opaque when stained is, the staining material has more body than it ought Very good stains can be made of burnt sienna and Vandyke "brown, in certain proportions, but Stephens' are more transparent. I ace the "Welsh Shepherd" recommends one coat of oak varnish. Is he aware that it will not stand long out of doors, and some of it is the veriest rubbish possible. Stick te the boiled oil for the outside, two or three coat, of it -, never mind beating it-. If heated look to your brushes, or you may get them burned up by the hot oil. "Pinaster" may depend upon this information, as I have bad experience for these last 24 years as a house decorator. All wood stains do not get darker in course of time; ■of that 1 am quite positive, and do not wish to mislead.— GlLDEB.

[2138.J—HARDENING MILL CHISELS—I advise •G. Doubled*.- locoathls mill chisels with finelypowdered p u siate ot potash, make them red hot, and plozuj them into urine; then brighten and Cemper.—A.: Iwirio.


continually in water, and I am told the water has no
effect upon them.—Non-adhesive.

some one describe the modus operandi for.covering
the surface of felt and amadou with isinglass, Ac.?—

[2145.1-RKPOLISH1NG A VULCANITE WATCH CHAIN.—Will some kind reader Inform me how to repolish a vulcanite chain which has become deadlooking with wear, so as to make it like jet again 7— A Country Vicar.

[2146.—VENEERING.—Will one of your subscriber, kindly inform me how to veneer a table, Ac, and the tools required ?—H. E. D.

r2147]—BENNETT'S CHUCK.—I would be much obliged if " J. K. P." would explain Bennett's chuck for the benefit of myself anl fellow reader, of the Mechanic. Also if he would meutlon a way ol keeping the mandrel of the lathe still when using the division plate and index.-KENMNGTON Amateur.

[J148.1— TALLOW. — Will some brother resder describe the best system of refining ships' grease into tallow?—Young Beginner.

[2149.]—SURVEYING.—Can aHy reader tell me what book will give the best help to make surveys and valuation, of dwelling houses and land to be mortgaged toe building society?—Reader.

[•2150]-LIGHTING GAS LAMPS BY ELECTRICITY.—I have heard that a means has been discovered of lighting street gas-lamps in a town simultaneously with electricity. Can anyone tell me if suoh a system is in operation, now, whero and .how it is done ?—Canadian.

[2151.1—HARDENING MILL BILLS.-Will any reader Inform me how mill bills for dressing French stone, are hardened, end what I. used for hardening ?T. Marsh.

[2152.1—PAINT ON BICYCLES.—I wish one of your many subscribers would answer me these question. :— How Is paint put on bicycles?—iB it common oil paint? and what give, it the glazy llook? Is it some kind of varnish?—A Subscriber.

[2153.]-VERTICAL SAW FRAME.—Would .ome
fellow reader give me some information on saw
frames? I have some large oak trees 2ft Sin. through,
and I intend to put a frame to cut them. Explain
the different parts and what strength to make them
—it will have to cut 3ft. logs down :o lft.4in.—to take
in any number of saw. up to foutceen. Also the best
way of fixing the log. while being sawn—the logs are
mostly round, and will want good fixings. Give the
length of stroke. The weight of foundation required.
—J. T. W.

[2154.]-HARMONIUM-TO "ADEPT."-I am
1 trying to build a small harmonium with two rows of
reeds to represent four stops, and I should esteem it a
great favour If our good friend "An Adept" will
advise me which are the best reed,
to purchase for a small instrument,
also where I can purchase them, also
if the feeders will act aa well on the
bottom board of case; If so, that will
save me much room? I also should
be much obliged if he will favour me
with a sketch of his silent feeder
valve for bellows that was named In
January 14. as my valve, make more noise tbat I like
to hear.—W. D.

How can I make this in a dry state,so that it will
keep similar to the albumen of commerce, that i. in
flake, very like sbellao 7—Lac.

[2156.J—ZINC ASHES.—What are zinc ashes, where can I them, and what is the price per ton? —elder Kin.

[2157.] — AN INSTRUCTOR FOR PLATELAYERS.—Will some of our brother correspondents Inform me where I can „'it a book that will instruct me how to set out a of any dimension—say from one chain to one mile, and the proper distance from a pair of points to a crossing of say one in two upwards? Whut I mean ia the correct radius from the point, to any spread crossing for a permanent way, I think there is a book as an instructor for platelayers ?—Unlearned Platelayeb.

[2158]— ARTIFICIAL LEG. — Will some kind brother give me the drawings, and inform me how to make an artificial leg below the knee, and what is the best material to make it of ?—W. R. E.

[2159.]— CLAMS.—Will any reader show me how to construct a pair of clams for 'splicing or jointing leather—such as those used by roller covcrer.? A diagram will greatly oblige.—T. Simmb.

[2139.]—HARMONIUM.—Would some kind reader tiate how many rows of reeds I could have for an harrooulum, the case of which is the size of a fiveoctave Alexandre's make? If some one would state bow I could fit it up with two rows T should be much

obViztd, and, likewiso. what kind of reeds, Ac. would

I* rkraired, aa I am entirely ignorant bow to proceed;

but haling made the case, bellows, <tc, I want to finish


[21*'.]-POOR LAD'S QUERT.—Will sone kind astronomical reader advise me? Having but very limited means, I thought of purchasing one of Wtay's JJin object glaanes, price £2, but seeing in our last Dumber that a 5m, specula would cost the same. I am rather Jn a fix which to have, and abould esteem it a favour for a gooi opinion.—A Poor Lad.

[2141. j—SPLITTING QUILLS.-How can I split quill* in half—I bare tried several means without success? Should tie quill, be soaked or aof tened ?— Cbowqcixl.

:<2H2.}-SOFTENING CAST IRON.-Can I soften cast iron before turning? I have a face-plate to turn; •Beg so bard, the tool will not cut it.- G. B. K. jat3-}—GLUE TO RESIST WATER—Could yon ■B me of a glue tbat will resist water, or of any compstttion for fastening wood together, so aa to resist *at»r! There i. a Arm iu London, I think, who make ■ejeks lor carpet printers; these blocks have to be put


to make a good paste or cement fur clothing iron rollers?—!. Sihms.

[31620-8E AMS OF MACINTOSH.-Can any fellow reader tell me what Is used for joluing the seams of a macintosh or waterproof cost?—G. W. D.

[2163.1-LEATHER BAG MAKING.-Would soire one tell mo how to make small leather cases—such case, being made of paper and covered with leather by gluing the leather on the paper cases—suoh as are now used by ladles and geutlemen ?—T. H. P.

[2164.] —PHOTOZINCOGRAPHY.— Will somo of your intelligent correspondents be kind enough to favour me with the titles of some of the bent books on the subject of photozincography and anastatic printing?—I desire to know ths "ins and outs" ol the printing.—W. H.

[2165.]-W0RK1NG MEN'S KXHIBITION.-Can any correspondent say if any employer Is eligible to exhibit an article of bis own invention in tho forthcoming WorUng Men's Exhibition, and say to whom to apply forparticulars?-MORELiOHT.

[2166.]—MAGNET.-Can I make a magnet by battery power? Will Smee's battery do; bow many cells? My magnet Is 71n. x ljiu. x {in., hoiseshoe-shapc, tempered steel.—J. Gabell.

[2167.]—LATIN.—Can any brother reader Inform me if there is a system for self-teaching Latin ; where I could obtain it, and what would be the cost ?—A New Subscriber.

r2188.] — DIMENSIONS OF MODEL STEAM ENGINE.—Will some brother reader give me tho dimensions of fittings for a model steam enginecylinder 3in. stroke, ljin. bore? What size steam pipe should I require, and leegth of lever for safely valve 7-R.R.

[2189.]-PROBLEM.—Draw a line D E parallel to the base B C of a tiiaogle A B C. so that D E is equal to the difference of B D and C E.—P. B. McG.

[2170.]-AN UNANSWERED QUERY.—Will some correspondent tell me how to blacken old copper oolns? This query was asked some time since, but has not yet received any answer.—Gitcue Sianito.

[2171.]—BORING MODEL CANNON.-l beg to return my sincere thanks for the instruction furnished on the above subject. Being unable to make the halfround boring bit referred to, will either of my kind instructors be geod enongh to inform me where 1 can obtain the same?—J. S.

[2172.] - BINDERS [CUTTING PRESS - UNANSWERED QUERY. — WiU anyone oblige by giving a description of cutting press referred to by "J. J. A," query 1467? I can bind first-rate, but cannot out with an ordinary knife. It would uo doubt confer a boon on many of our reader..—Mabchil.

[2173.]—GAS'WORKS.—Will " Rotherwood" be so kind a. give a few more particulars about his economical gas works in Reply 17.11, p. 613, as to construction and operatiou in gas manufacture; also where the E. G. works are to be had?—Johannes.

[2174.]-MAGIC LANTERN AND MICROSCOPE. —I have a magic lantern with 3|in. condensing lenses and Bhould bo glad to know what would oe the cost of a good microscope to attach to it-suitable for showing animalcules In water, Ac, Would a powerful lens. u> burn camphorated paraffin give a disc of light sufficiently large and clear to show microscopic objects to an audience? Could the same instrument be so adjusted as to be used iu the daytime as a solar microscope ?—Frayer.

[2175]-LIFTING POWER—Has the wedge or the .crew jack the most power in lifting?—T. H. H.

[2176 ]—BLAST FAN.—I would esteem it a favour If one or more of your reader* would give me some information as to the construction and arrangement of a blast fan suitable for a smith's forge fire.—C. T.

[2177.]—PROBLEM.—With a point in the perimeter of a given circle for a centre to describe another circle, an arc of which shall divide the giveu circle into two equal parts.—Indagatob.

[2178 ]—CIRCULAR DISC—What must be tho size of a circular disc to be fixed on its centre in the boundary of a circular orifice lft. iu diameter, so that exaetly one-half the area of the orifice Is covered by the disc ?—Indagator.

[2179.]—GRINDING SPECULA.-Will steel, iron, and metal make a tool to grind and polish glass specula? For the purpose are the grooves cast or cut in the grinding tool? Can a glass speculum be ground, If firm, level and stationary? Is it possible to grind a .peculum parabolio without first grinding it spherically r—Andrew Johnson.

[2180.1-ENGINEERING IN GERMANY, Ac—Is there a mechanical or engineering sohool or college in

[2100.]-PRESSURE ON COLUMNS. — Will any .,„,„.,„„,,.„

brother subscriber tell me how many tons'pressure Germany whero pupils are instructed In practical as four iron columns will bear standing upright as shown, well as theoretical engineering, and where? Thanks

to Mr. Biggs for his answer to query 1934, and may 1 1 a»k him if he will kindly furnish mo with a solution of the following, whioh appeared in the Science and Art Department examination papers a few year, back?—" If an arc of a circle measure 50ft., while the radius is 18ft., what is the area of a sector whose base is tho given aro»—Y. P. W.

[2181.]—DERBY CEMENT.—Will some one oblige me with a recipe lor Derby cement for mending jet, vulcanite, china, or glass ?—G. S. H.

[2184.]—CONSTRUCTING COILS.—I am about to make a cofl, and intend to use about six mile, of No. 36 copper wire covered with silk for the secondary. I want to know what length of No. 16 cotton-covered copper wire I should use for the primary, alse about what number of sheets of tinfoil lft. square would go to the pound? I also want to know what length of spark I could get from the coll, also how many of the bichromate ..f potash bottle-batlerles ought 1 to use? Is wire, covered with composition, better than sUk or cotton-covered wire, or would wire, covered wiUJ ootton first and thee with the composition, be sun better? Is there any substitute for gutta P"0" tissue, and what kind of cotton or silk is used tor In plain figure. 1—W. R. E. covering the wire In shops whero it is sold covered .

[2161.] - PASTE FOR CLOTHING IRON 1'he.e last three queries I havo ofteuseeu asked, DUt ROLLERS.—Will any reader please to tell me how have never seen them answered. -»""■


[218...J- TAXIDERMY. — On application for th<> work men'ioned by your correspondent, I find that it has beeu out of print for 20 years. Can anyone inform me if there is any other published, and who by?— Sold.

[21*4.]—SULPHATE OF LEAD BATTERY.-! will feel obliged to any of your readers who will be so good as describe how these batteries are made I understand Moseley's patent battery consists of copper caps tinned, and flx-d on a central wire. Is it actually necessary to have the cups so tinned? and is a porous cell requisite? Would a notation of sulphate o( lead not do to charge Smee's cells with? "Sigma" has promised a description of all batteries now known or used, but it may bo soni* time before his papers bring him on to that part of the subject, aad in the meantime many of your readers as well as myself may be at a standstill for want of the Information. —Fronti Nulla Fides.

[2185]-MILDEW ON- ENGRAVINGS. — I shall feel much obliged if one of your correspondents will inform me how to remove mildew from picture prints*, and how to prevent it.— Cosstant Header.

[2186] - BAROMETER TUBES. — Thanks to "Jbnalh" for his Information on the safety valve. I have dome barometer tubes fnew ones), and lu laylmr by they have got covered with a film inBide that makes the mercury look muddy when it is put in. ("an anyone tell me the best way to cleau them ?—CompensaTion.

[21S7-3-NAPHTHA AND GAS TAR.—Would any brother subscriber give Instructions for making naphtha and anything else that can be made from gas tar, with a description of vessels, &c, required for the same? About 80 gallons of tar is as much as I intend to use for that purpose weekly, which will, perhaps, give an idea of the sizes of what will be required.— J. H. M.

[2188.]—ORNAMENTAL WOOD AND METAL CUTTING MACHINE AND VELOCIPEDE. — Having for some time eecn advertised In onr paper Cunningham's fret-saw, drilling apparatus, and kinograph, I should like to have the opinions of a few of our subscribers who may have tried them as to whether they are useful machines, well made, of good metal, worth their price, and, in short, all they profess to t»e. I should also like the opinion of some of our velocipedtsts if in every case a driving-wheel above 3o*ln. ceases to be an advantage. I have an ordinary 3flln. and 33in. bicycle, but I want to get nearer the ground, and I think of reversing it, so bringing the small wheel to the front and making it the guiding wheel, and putting the wheels farther apart and driving It by a crank working in a bearing between the wheels, and communicating with the i driving wheel (the hind wheel) by a connecting rod as outside a locomotive; or with a pedal working like the elaow jointof a bell-pull and connected as before: shall I use my old wheels, or have the driving-wheel larger—say 6ft., and, perhaps, the front wheel smaller —say 2ft, and which driving-gear shall ltuie ?—Gim


[2189.]—CIRCULAR RAIL.—Can any reader inform me how to make a circular rail for a model locomotive? It must be constructed on a framing of some sort, so that I can lay it on the floor of a room without injuring theeurpet, »tc—F. G. C. * [219-M—THE ORGAN. —Can any brother reader toll me the way in which an ootave coupler is made? also how a composition pedal Is connected to the stops f A drawing of each will oblige.—Organise.

[2191.]-TTJRRET CLOCK.—Would Mr Maddlson kindly inform me what advantage he gets in the nse of cast Iron wheels in his clock instead of brass—moBt generally used? I never sawoue erected successfully with Iron wheels. I should thluk that an Iron wheel working it a pinion of Iron or steel would work harshly together, and also be liable to stop through rust collecting between wheel and pinloH.—Tintac.

[2192]-SULPHATE OP AMMONIA.-Would Mr. G. Davis, or some other among your talented correspondents, inform me of the most improved and simplest way for finding the degree of strength of sulphate of ammonia ?—Basin.

[2193.]—FINE CHARCOAL.—Can any subscriber inform me where 1 may obtain fine prepared charcoal for rubbing down silvered circles, &o. ?—it Is generally in short square sticks.—Termus.

[2194.]—INTENSITY COIL.—Can any fellow reader inform me how to make a small Intensity coil powerful enough to fire gunpowder?—Coil.

[2l95.]-SMOKELESS LAMPS.—Would nenry W. Reveley, Reading, who sends a sectional drawing of smokeless lamps without a chimney, in your journal of Jan. 21, 1870, kindly furnish particulars as to construction, length of cone and hollow globe, aad bow the wick is raised or lowered?—Practical.

[2196.1-NAMES OF PUBLISHERS.-Is there a book published entitled "Annals of the Wars of England ?" and If Bo, please name the publisher and price? If not. I should like to know the name of the publisher and the price of the " Annals of the Wars of Europe.'' What would be the most simple work on bell-ringing, the publisher, and price?—H. G. Redditch. p[2197.]—TO GEORGE E. DAVIS.—I wish, through the medium of the English Mechanic, to thank G. E. Davis for the information he has so freely given, and to request him to give me further information on the following points :—1. How to estimate sulphuric acid iu salt cake? 2. How to separate barium from strontium? 3. How to estimate chlorine by volumetric analysis? 4. How to analyse roughly a sample of patent manure—such as Standee's? 5. How to estimate the ammonia in a sample of manure ?—


[2199.1-BORATB OF BARYTAS.—Could any correspondent give me a simple plan how to make borate of barytas ?—Haslet.

[2199]-TELESCOPES.—Will "A. R. TM" p. «14, or any other of your correspondents answer me any or nil the following questions: —1. What is the probate reason that I cannot get a good view of the suu's spots with one of Solomon's £5 telescopes? 2. What

will be tiie probable cost of putting a rack on the focussing s'ide of the above telescope? 3. What will be tho best and cheapest way of mounting one of Solomon's ,C6 telescopes on a stand, the legs to be made shorter when not iu use? Perhaps "Pollux,'' on p. 60*. will be able to give some information about a suitable stand for a working man's telescope, as he ceems to know what they have to put up with when they cannot afford the more elaborate and costly workmanship of an Equatoreal stand, viz., the primitive and uncomplicated mechanism of a brick wall, and the elevation, depression, and sideral motion of the instrument as to be performed by muscular power?—H. F.

[22000-ENGIXE AND BOILER FOR LAUNCH. Will any of our friends, having experience in such matters, kindly inform me what style and size of engine and boiler is best calculated for driving a launch 36ft. long by 9ft. broad, with number of blades, pitch of screw, and probable cost ?—Solicitor.

[2201 ]-STE AM ROARER —Will some kind reader inform me how to make a cheap and simple steam roarer to act In place of a bell for a mill? I should also like to know if it is obliged to be made of brass? There was a plan of a steam whistle in the English Mechanic a short time back, but the drawing wns very small. I failed In making one off It that would act, so I wish t« have the plan and dimensions of one of those sort called a roarer, which are so much uaed now for works.—Yol'no Engineer.

[2202.]—WHEEL SKATES.-Will some brother reader kindly inform me the best plan for waking wheel skates?—C. Francis.

[2203 3—FLOUR DRESSING MACHINE.-I am trying to fit up a small machine so that I can run down a few sacks of Bccourts flour whenever my other machine is broken down, and occasionally a tew grists. 1 have made a 12in. cylinder which will take three sheets of flour wire and one of sharp wire? What number of wire ought I to use, and how many brushes, and what fall ought the cylinder to have ?—A Country Miller.

[2204.1—PROBLEM.—The diameter of the plate of a hydrostatic bellows is 12ln., a weight of 2501b. is placed upon it; what will be the height of water In the pipe?—W. B. S.

[2205.]—PROBLEM.—What <s the atmospheric pressure when the barometer stand* at 30in. ?—W. B. S.

t220».]-CERAM«o MANUFACTURE—Thaaki to "Beta "and H. B. Miller for their information. On luquiring, however, at Barth's and Quarfteh's, f And that instead of 20s., 23s., Ac., Brongntari's book Is 50s. Are there different editions at different prices? It is not needful that the works sought should be In French —a good practical English or French book at a moderate charge, especially if treating on the preparation of colours for painting, and printing, is what I require.—Iota.

[2207.]—CBJCKET BATS.—How are cricket baU made? I have tried my hand at one several times and failed ?—A Subscriber In Canada.

[2208.]—REFINING BEESWAX.—Some time ago "Feu Foliet," in reply to "Pulp Maker." offered to detail the process of refining with chlorine: would he please do so, as I wish to try my hand at it?—A


[2209.3—OVERLAND ROUTE. — Will "Selwyn" explain why, if the Overland route via Marseilles Is also via Southampton, the " Postal Guide" makes the distinction of the routes for letters, thus—India via Marseilles Is., via Southampton tfd.? Hew do the Ud. ones go ?—Iota.

[2210.]—BAR MICROMETER—Might I ask Mr. Proctor or some obliging correspondent to be kind enough to favour myself and your innumerable astronomical readers with a drawing or description of a bar micrometer and its field of view, and explain its uses? What is the difference in use between it and a ring micrometer?—Iota.

[2211.]-OBJECT GLASSES. —Referring to Mr. Purklss's letter on t'.s subject in the English Mechanic for MarcL 4th, might I ask him to be kind enough to say lu what year he knows -J* Andromeda to hare been divided by Mr. Buckingham's instrument with a powers* 2' ?and alae it'he ran inform me how many seconds apart they then were, and how many at the present time ?—Iota.

[2212.]—SPIRAL SPRING.—Is the spiral spring reliable as UBed for steam pressure gauge*? I presume that steel springs are only useful within narrow limits—say a range of 40lb. or .'.01b. What I want is an extremely accurate means of registering pressure, increasing by a pound at a time, between the two extremes I have stated. I suppose this might be done by communicating the pressure to a hand travelling round a well-divided dial, but my difficulty is in what way to communicate it? The principle of the steelyard would seem the best way of applying the weight for the division of the dial. Can anyone suggest a better?— F. Q. Q.

[22l3.]-STANWAT'S VELOCIPEDE.—I hope Mr. 8 tan way will answer a few questions respecting his velocipede—a description of which is given in the Mechanic for March 4tb. Does he propel his velod

Sede by means of his feet as well as his bands? aud ow does he manage to steer it, as the handle appears to be fixed between the levers, In consequence, there would not be room to get it round a sharp curve? Is it steered with vhe feet or hands? What is the distance between the front wheels? Please to describe the method of steering, Ac.; also what is the price of such a velocipede, and the name and residence of the maker? If he will describe how it is constructed In front as well he will much oblige.—An Admirer Of


[2JH.]—CANOE.—I am about to build a canoe. Would some reader kindly let me know where I can obtain a book containing practical information on the subject?—('. D. Richardson.

[2215.]—STAMPING SHEET BRASS.—Can any reader tell me how to tive brass the appearance of bronze, aud where I can get dies made for stamping sheet brass ?—Tyno.

[2216.]-CARRIAGE PAINTING.—Would someone kindly Inform me how the paint for carriage work

is mixed? and also how to mix the paint for strip* og: —Young Painter.

[2217.]—WHAMPOOM MONEY. —Our Enoxish Mech Anic has spoken several times of Cowrie nosey or shell money. 1 nhould feel obliged for soiof Information on tho Whampooms of North Antcrirtt.— Pioneer.

[2218]—GEOMETRY —U there any genmetricaJ means for proving the following theorem ?—Raving; three circlet on a plane, and drawing tangent* amnion to t wo, those common tangents have their intense tions on the same straight line.—X. X. *

[2219.]—SIL1CIOUS GALENA.—Could some re&Acr givo me a few details on the modern methods t*t reducing silleious galena, also on the substitute* for nltro-glyoerfne (blastingpurposes)?—Feu Kollbt.

[2220.]-SOLDERING.—I want to solder a 2uj. c»*t Iron pipe to a -.'iu. lead pipe. I find a difficulty la tinning the cast Iron pipe. Can any friend iaforra me how I can do It?—G. D.

[2221.]—SHORT SIGHT.—Are there telescopes sold for short sighted people ?—Ethahdo.

[2222.]—REDUCING LEATHER TO PULP.—Do you or any of your chemical readers know of a anlTeni that will reduce solo leather to a state of past*?— W. W.

[2223.]— ENGRAVING ON SLATE.—What kla<2 of knife or graver Is employed, to engrave the lines aad figures on a .-late sun dial .' A.S,

[2224.}—BOILER.—Thanks to "Vivas Sperawdnm'" for his kind answer to my query, but will be be kind enough to Rive me a few more particulars? 1. CorrlcS I not pat in tho feed cistern at once without pipe anri funuel as shown? 2. What would be tho quantity for 50-horse power boiler per week (751 hoarai ; prolan', 4511k? The water is very much impregnated, with lime; scale very hard—like porcelain almost. 3. Ran my brother reader ever tried carraqun in a hotter much incrusted, for my boiler Is very intricate ?—0*t In A Fix.

[2225.]-VACrUM IN CYLINDER. — Will' some brother reader kindly Inform me If the exhaust steam on leaving the cylinder of a high-pressure engine causes a partial vacuum, or has the piston to be forced against the full atmospheric pressure, or 151b. on the square inch?—Vacant Head.

[2226.]—TINCTURE OF IRON.—How Is the tincture of iron used In medicine made, and what complaints 1 * it supposed to cure ?—Vacant Head.

[2227.]-LlFE BELT.—Whore can I get or bowcould 1 make a life belt for boating purposes ?—Ava


[222*]—ADDRESSES WANTED.—Will any kind English brother reader give the lull addresses of some of the most important coal mines in Great Britain ?—A Fokbiom Correspondent.

[222"}—WORKS ON CHINA GRASS.—I want same good works on China grass—either English, KrenfA. or German, Ac. If a brother correspondent will answer my query, stating purchaser and price, be will much oblige.—A Xellibt.

[2230.]— REMOVING FLY SPOTS.—r hare a rerr fine old engraving, but, unhappily, quite eorvred with fly spots. How can I remove tbem? I have tried several ways, but failed.—Peba Y Mopebba.

[2231]—ENCKE'S COMET.—Will you please be good enough to ask " Omicron" to explain what is meant by solving an equation by the method of le**t sqaares—an expression that occurs in his acconutof Kncke's comet ?—T. Waghorn.

[22y2.]-PROBLEM.—Can any reader favour me with a solution of the following problem from Todhunter's " Smaller Trigonometry, chapter X. :—The hypothenuse A B of a right-angled triangle Is divided at D, Bo that A D is to BD as C B is toXA. £how that a? v «* + o*

tanACD = — CD =

l* a + b

—J.M. Small.

[2233.] —STAFNED GLASS. — Will Mr. Joaepb Leicester or aoine other able correspondent inform me how ornamental church windows are painted, and stained, as I have a little knowledge of some pnri, except ingredients that are used? I know there* u a reddish orown colour painted on the glass for opique and shading purposes called tlux—It is mixed with turpentine. I want to know what It Is composed of; when It Is burnt in a kiln it 1b very hard, and cannot be scraped off. I want also to know what ingredient* are nsed to stain plain glass In parts where wauted, such as yellow, blue, &c. For windows, as above, I have seen glass when taken out of the kiln with a red colour or deposit on them, and when cleaned of! leave a beantifnl clear yellow stain on the plans—accordingto the design painted on.—Gustavo Knox.

[2234.]-TO "JUPITER."-Will "Jupiter" kindly tell me where he procured his 31n. refracting telescope of which ho writes in evident praise In the last ls>ue of the English Mechanic, and what he gave for it .* Will he give me his idea of the apparent diameter of Jupiter as seen by him with a power of 75? 1 have this moment completed some observations with a Gregorian of 4ln. apartnre, and a power of about TO*. Jupiter certainly did not appenr to rae to be more than tin. in diameter, nor could I detect more than a mere suspicion of the " belts," but tbeu It was not a good night. Will "Jupiter" kindly tell me the highest power his object glasB will advantageously bear, and the apparent diameter of the plairrt "Jupiter" has seen with highest power? Thin wfli supply me with a point of departure from which I may deduce for myself other measurements.—Fin Mr*.

[2235.]—HOSIERY YARN.—flow can I double and twist two threads of hosiery yarn \irom one to lour per inch ?—Tinker.

[2J3«.]—DIRTY CEILING.—Can anyone tell mo why tho Joists showthrough dirty ceilings, i.e . whenever a joist is the celling is much cleaner than the space between them, which gives it a ribbed appearance?—Minnehaha Igitciie Manit*.) [2237.]— SALEKATUS.— What is It?—A. P. R

[223N.]—FORMULA FORCALCULATINO POWKR OF .siMKAL SPRINGS.— trould any reader ktn i iy

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