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tee how to nso It. There is no centre point, and the Attorn edge is not In a line with the outside marks Vm someone tell we in which the fault lies-me or the protractor ?—R. W. R.

rsWi-BLAOK LEAD.-How can I make Mack lead Into small blocks, same as Ntxey «?—« • »• "■

[SMI 1—SWEET GUM.— What gnm Is called sweet znm in the United States ?—C. D. P.

r.j9#.. ,_to " M. P. 8."—Thanks forreply relative to diirUaTiii I observe the formula you quoteie In half ■1 Amities of the process given in one edition of he t p 1 have been considering, and have come to the M.ne'in«ion that I must have been wrong in the acetic ac\d treatment. Tbe woida in formula are. treat the extract with Soz. of water acidulated with the acetic acid. Sow, not auv special aolrt or mode of treatment ^jcAue stated. I used glacial acetic acid In 5oi of. dt«tilledwatertnarle pretty warm ; this, Icouclude, is the cause ot the whole uniting intoahomogenoous mass. Ought it to have been a weaker acid, and the extract rivaled cold" Is there auv work on the above compound* .'—for most of the chemical and pharmaceutical works which I am acquainted with ontalii but very litrle relative to this Important class of bodies, even "Miller's Elemeuts of Chemistry." part 3, embrace but a small quantity of them—PharmaceuTical ITtjnEST.

C2243 ^-CONSTRUCTING FERH CARE.—Will any subscriber oblige bv giving plain and simple instructions how to make the above ?-fbbn Lover.

r2244]—RF.FRACTING TELESCOPE.—I propose constructing an achromatic telescope 18ft. Sin. focal length • the glass 1 propose using will require the .-rovvn lenee '« be Oft. loin, local length, to correct the chTomatAe aberration. Will our learned friend .. ^> ^ A.s." give me a set of curves for this combination? If any other gentleman wrmld furnish a set of eurvei also, it would be esteemed a favour.—Nep

•JD1TB.

1224SJ—TIN SOLDER FOR GLASS—Can any rBBder inform me b>w to cause tin solder to adhere to gf/uie. as I often see glass brooches soldered on the back ?—G. Gebhi-.

[22*».n—STEAM WHTSTLK.— Can any friend tell rue the way Co make a steam whistle for a small model engine? A diagram would oblige.—G. Gebhev.

C224?.]— TICKET WRITING.—Will any of your readers inform me as to what compounds and what ^aantittes are used by ticket writer* to make black ink, also what for red ink ?—T. W.

f.23«.l-SPEED OF AIR AND STEAM.—How can \ calculate ihe velocity with which air rushes into a vacuum? also what is the velocity of steam issuing from a pressure of one, two, three, or four atmospheres respectively ?—CENTBir Uoal Korcb.

[2249 i-MT SHAPING IN THR LATHE —Would *' W. H >*." be kind enough to answer me one question? By what means is the nose-piece fixed {for csnTfog-the nuts) to the end of the splodlo that passes throoiru the square boss, or if the thing is of solid steel?—CEVrRirucAL Force.

p?250]—THE EAST WIND—Can any of your readers. Inform me if it has ever been satlsfac:orlly proved that the unpleasantqaality of the east wind » due to nnythiag In-side its dryness and coldness— say, to electrical condition? of the atmosphere during its prevalence? What Is the best way of counter acting iia influence within dotrs? Can someone refer toe to any honk containing a record of the temperature and prevailing winds of this country for the last century 7—Saepf.

[2351.] — RKNDBRIKG BONE BKMT-TRAN8PARENT—Can any fellow render kindly inform me aow to render bone semi-transparent as we see It in imitation of amber upon tobacco pipe stems ?—Amber Tb>.

[SI.]—DISPENSING QUERY.—Can onoof our M. «a.p. S.'s tell me how to make a perfectly clear ■aaaare of pepslne porcl, S8gr.; acid, muriat. 12scru.; sv*ia,4dr.—A. P. S.

WrTACHT BUILDING—Will somo brother resder *t\e the name of a book on yacht huildiug which rrrej drawings of models to scale for small yachts about 5 tons or so '.'—Steersman.

f22.H.j-I*>ORS.—Will waluut timber require much seasoning brfi.re using, and if it is u kind of timber adapted /or doors, Ac., and if the labour of working It la equal tbe price of onk?—Shrinkage.

[22S5J-IKON CISTERNS.-What number of bolts would ft require for bolting flanges together lu 12iu. length, and also the weight ot red lead putty per foot ran, or is it usual to allow so much per cwt. the r-Ulern weighs of each kind respectively ?—Fitter.

[2256.J-CI.EANSING CASKS.—Ihave a number ef eapty beef barrels. The salt from the pickle has ■aluratcd 1 he staves, and when wet weather comes tbe «Jsks become damp or sweat— some of the casks smell aai Can someone inform me how to oure these evils?

ae caeka are to be retilk-d with liquid.—W. Ebdb.

(2267.]-PA PE It NKGATIVES.-I should feel much obliged by " Mus" giving me some information as to •aking large paper negatives. I have a 6in. aplnuntic lens by Grubb. I have worked waxed paper, plain paper, and paper saturated by liquid paraffin. I can ■ret very good results by these methods, especially for pictures 30in. x 23in., but whit I wish for is to know some method and an easy one of getting the negativo on the surface of the paper instead of in it, as it sometimes happens the grain of the paper, unless very good, shows somewhat coarse and woolly. I certainly have got somo good pictures from good waxed paper nearly up to the mark 01 the sharpest collodion picture, Lot I facny linprovemeuts can be made in this direction if "Mus " or the photographers which read our journal were to experiment. Unfortunately. I have no time to spare to do so, but should be glad of anyone's experience iu this matter. —Gilder.

[22B8.]-EQUATIONB. — On p. «40 ef the last volume, Mr Biggs very kindly promises to solve a simultaneous equation of three unknowns if our obliging editor will only allow the space. As one

eader. I ask for the desired space. At the same time I append two equations which I cannot solve in any way, aud shall be thankful for any help towards arriving at any easy solution. I havo not tho least idea what room tho working may occupy :—

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WORKIN'G MEN'S COLLEGE.—The spring term of the Working Men's College tins Just commenced. Klcmentary and advanced classes were formed in arithmetic, algebra, geometry, book-keeping. English. French. German. Latin, and Greek crammar and literature, English history, the use if the mlcrosjopc, astronomy, physiology, music, nnd drawing.

IRON CHIMNEYS.—A wrought-iron chimney ItWft. high and 6ft "In. in diameter has Just liecu erected in PittBburg. Another i« to be put up Wift. high. The first was rivctted together in a horlaonU! position, and then lifted to the 1 erpendlcnlar by a crane. The other will be made upright: the plates will bo rl vetted by means of a scaffolding running up inside.

A NOVELTY IN BUTTER MAKING—A singular nie'ho'; of making butter has receutly come into rather exteuslve use in France, based upon the fact that cream is changed into butter by betn?- simply burled in the earth." The theory of this result, says the Grocer, is not very iutelllglhle, though the fact is stated to be beyond questt<in ; and in Normaudy and otl'er pa-ts of France, butter is prepared on a larpe scale this way. The process consists in placing the cream in a linen ling of moder.it« thickness, which is carefully closed; then bun Ing the bng about a foot and a half deep In the earth, and allowing It to remain from 24 to 25 hours. After tho expiration ot this

fieriod, the cream is found to havo becomo hard, nnd t is then broken up by means of n wooden beater into small pieces, and sufficient water poured in to wash out, the buttermilk. To prevent anv mixture of earth, it is advisable to enclose the bag in a second one of larger size and coarser quality. . ''Is method of making butter saves a good deal of labour, and separates the butter more perfectly than the ordinary process •, and it Ib snid that butter thus prepared is of a more excellent quality.

A FLOATING TELEGRAPH STATION—In a few days a telegraphic stniluu vessel w 11 be moored bv the interuatiounl Mid-Channel Telegraph Company nt the entrance to the English Channel. I'i from 55 to ftp fathoms of water. In latitude 4'J dec 20 mln. 31 sec. N, longitude fl deg 17 sec V,'. of Greenwich. The vessel will be painted b'nek. with the words "Telegraph ship" in white letters on her sides; she will have three must.*. At the top of the mainmast a large black cone will be hoisted durlrrg daytime, aud a powerful globular light at night, elevated 3"ft. above the sea. wlil-ti in clear weather should be s-on from a distance of « miles. A flare-up light will he shown every 15 minutes during the night from an hour after sunset to an beur before suurlse.. During I'oggv weather, day or nfght, n bell will be rung continnou ly for half a minute every qu rter of an hour: nnd for the first six months,or until the 1st day of October. 1S70, a gun will be fired every quarter of an hour, nnd a'ter that date every hour. The commercial codeof signnls for the use of nil nations will be used on hoard, to the exclusion of allother codes, and none other can be noticed.

MORTAR —The disadvantages arising from those kinds of mortar at present In use are chiefly owing to inferior eand being used, and the grent difficulty of obtaining sand at a moderate pr»ce. A material has been invented which does away with tlsese difficulties, for whea used it requires only'to be mixed with water. In order to m ke one tun or this mortae. the following substances should ho ground by machinery: 2881b. of lime (either caustic or the hvdrate, 17281b. of Blag, and 2241b. of calcined coal-shale clay. These material" having been ground to the degree of finenoss required, are mixed, and are ready for nso From the nature of the substances used, there would be. doubtless, a mote ratdd chemical action than thnt which takes place in ordinary mortar. For plastering purposes the compost seems to bo eminently suitable.

TIN IN CALIFORNIA.—The Chief of the Cabinet of Practical Geology and Mlniug of t*e United States General Land Office, hits very recently written a letter stating that additional Information in reference to the discoveries of tin In San Jitcincto. San Bernadlno county. Cal.. haa been received, and specimens of tho ore have arrived. The analysis of an average specimen by a competent ohomrgt and mineralogist shows that the ore contains I3*:j" per cent of pure tin. The ore is intermixed with tourmaline, containing boracic acid, and with casslterlte. This combination is reported to be unusual aud highly interesting, aud the yield of tin is double that of the ores at the C irnwali mines.

ACTION OF MAGNETISM ON VARIOUS GASES. —M. Treve has communicated to the French Academy some remarkable results of experiments upon the action of tnsgnetism upon the vhrious gases. When the spark from aninduetion coil passes through a Gelsaler tube filled with hydrogen, the gas becomes luminous, having a blue tint, plainly violet nt the extremities of the tube, and of a flue red colour In a capillary prolongation. But upon placing the latter part of the apparatus between the poles of a magnet, the red lnstautly disappeared, giving place to a perfectly white light. In like macuer oxygen, whli-h gives a milky white light in the capillary tube, bocame red: urtrogen deepened its blue to a still deeper blue; tho brilliant white of carbonic acid became deep blue; tbe blue of sllicium fluoride became a bluish violet. The spectra of these luminous tubes changed whou thecapulnry portions were subjected to the action of inaguetism.

NEW METHOD OF OBTAINING GELATIN.— Crude animal substauces, such as tbe flesh, fat, skin, tendons, bones, etc., cither with or without a previous treatmeut with linio, nra treated with benzine, or some other similar hvdrocarbon, in a vessel provided with a condensing apparatus for saving any vaporised benzine, or In a closed vessel at an elevated temperature. After a few hours'digestion, the hydrocarbon solution of the lats nnd oils is drawn off, and may be treated by any of the well-known methods for recovering the volatile hydrocurbon, which may be agala used In subsequent operatlous. The oils and fats are saved and utilised. The animal matters, or purified glue-stock. Is now ready for conversion into gelatin by heating with water in the ordinary way.

INTERESTING FACTS.—A legal stone Is 1 lib. in England and In Holland. A fitthuui. 0 leet, derived from the height of a full-grown man. A hand, la horse measure. Is 4 Inches. Au Irish mile Is 2^40 yards; a Scotch mile Is l.flsl; n German, I,M)f.; a Turkish. 102t>. Au acre is 1810 squire yards 1 foot aud 34 inches each way. A square mile 1700 yards each way, contains 010 acrss. The hutnau body contains 248 bones, 9 kinds of articulation oe joinings, luucartilages or ligaments. W) muscles or toirdous, anil 100 uervea besides blood, arteries, veins, Ac. Potatoes plauted below three feel do not vegetate; at one foot they grow thickest, nnd nt two feet they are retarded two or three months. There nro nosolid roeksili the Arctic regions, owing to the severe frosts. The surface of the sea is estimated at l.'>o,ui>ii,0ir0 square miles, taking the whole surface of the globe at 1» '.OOVWo square. miles. Its greatest depth Is supposed to be equal ts the height oi the highest mountain, or four miles.

CHIPS.

SPIIEROLOCOMOTION.—This is a new system of transportation of goods, in cast Bteel hollow spheres rolling lu pneumatic tubes. A process patented in America and lu Europe.

SUEZ CANAL—At an Indian Conference at the Society of Arts on the 3rd instt., the influence of the Suez Canal on trade with ludia was oonsirlei-ed Uuring tho proceedings. Mr. J. II Sniltlr said. "India must improve her eotfom cultivation by irrigation, and then she could easily produce SOOlb. of cotton per acre."

TCHUAXTEPHC CANAL.—The Mexican Minister of Public Works has sent a letter to the Congress of Jlcxlfo, trnnsmltiln:.' the original project for concession for a ship canal through the Isthmus of Tchuantepec. Article I authorise" the Tchuautepce Hailway Company to construct that canal.

ANTIDOTE FOR PHOSPHORUS.—T)r. Anitant, of Dax, France, has suited thnt in six r»se« spirit of turpentine was an antidote for phosphorus.

A NEW KIND OFCOTTON.—A new sort of cotton called Bubuy is said to be produced in the Philippine Islands ; it is probably a variety of ISoiiAajc down.

CURIOUS FACT.—An Italian chemist has dlseorered that the animalsof several shellsof the Geuus Dolium. Tritonium, &c, have u gland uecietiug free sulphuiic acid.

THE ISTHMUS OF CORINTH —The concession for the Canal oi the Isthmus of Cotiulh has been signed.

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HtuEuoi will oblige by aending us hi. addres.. w L. Lahcabtrr.- Consult Index published in last number. A Comstaut Iuadrr.—Write them for a circular or description. r

Josim Godbull flpswich).—We only insert udvertis.ments

when they are paid for. }}■ CaowTHlR.-Try Sixpenny Sale Column.

D. L. Williams.—We do not remember cither of vour previuus letters. Sometime, we receive so many answers to one question that it is impossible to insert them all.

W. Lewis— Every number of our last volume contain, information about telescopes.

7yK,nHEK -Consult our advertisement pages.

n ?' Q—p,r,t "[)"""■ query can only appearm Sale Column.

C. C.—It would be illegal, and we could not therefore give the information.

F. Marsh—No charge whatever ia made. We have inserted a query for you.

GJ?' J10?1" 'GuelP,h; Ontario).-Your query is inserted. Thanks for your kind wishes. Recommend us to the Canadians.

S. T. Presto* -Would all depend on the merit of the article. we have no lack of valuable contributors on the subject but are always glad to receive really good matter

Caravan.-Your querv cannot appear (except as an advertisement). It would not in all probability be answered, nor would it interest anybody besides yourself

w.C. NoT-rs.-Answered very recently. We cannot repeat soolten. r

G' R~tf0^ qany inMrteo- Recipe, for harnes. and other blacking have appeared in back number.

SuMMiEH0USE.-M.ny lists of varnish have been given • some very recently. B

Rusticus-Indices, with the exception of the one published last week, are published, twopence each. For answers to other queries see back numbers.

J- T—You should have sent your address.

Y" ?ll1^ —Pr.cmi»ma .re gcnexally paid. Salary afterwards will depend on ability.

Mus.-If we felt inclined to give poetry, your very complimentary hues would be inserted.

1'. Forbes.—Your letter, or some parte of it, were illegibly written, and was therefore not sent to the printer's. Correspondents who write on technical matters and use technical terms cannot be too particular in their caligrapliv

Kobert Charnlet And A. L.—Something won."

J. W. Ward—Read the letter, and answers to querie. w hich have appeared on telescope..

J. W. I).—Consult back numbers.

s. J.—We have not time to search. Possibly the name you refer to was an assumed one. a

Atheist.-The insertion of yonrletter would inevitably lead to a profitless controversy.

Nomhe De Plume.-" Gitclie Maaito" doe. not wish ta rut)

•gainst the gram or aajone'. sensibilities, as indicated by

Sergms last week, and will, therefore contribute in

future under the name of "Minnehaha." One would

suppose that "Gitclie Manito" has read Longfellow's

Hiawatha " with unusual satisfaction.

J. M.hMALL.-Query inserted. Reply to 1935 not inserted for want of room.

W. S. T — Your query was not inserted because it was answered a short time since.

E. W D.—Can you not put a ring round the tree and fix the hooks in the ring?

1870.—Consult a few back numbers.

W. Pa Wson—Your request has been attended to.

Tiro—You must know that your request is an advertisement.

Toor Mechanic—Wc can't inform you.

Charles Kkvei.l—We believe your ««£ge.tion to be impracticable. 1 ry it, and let us know tli e result.

R. Rumsky.—No stamps enclosed.

Turret Ci.ocm.-Syilney Maddison, wlio wrote a short tims since on turret clocks, would oblige by sending his correct address to Mr. Lloyd, 135, Steel-honse-Une, Birmingham.

¥. Oisman.- Your letter came to hand.

PROBi.EMS.-Sevcral problems, and answer, toothers, arc

not inserted on account of the space they would occupy. Veritas—Ihe last letter appeared exactly as you scntitto

Wm. Morris.—Your Rntwer i. an advertisement.

W. Finch—No .tamp, enclosed.

Rotiierwood —On reference to our "Sixpenny Sale Column m this number, you will find a communication addressed to you.

N°*TB Bitchburn.—Can only appear in Sixpenny Sale

Tinker—No charge; query ia inserted in this number.

Cjuercus.—Must purchase indexes and search. We have not time.

R. H. Hull— We willingly insert free of charge all queries asking for information; but those which inquire for addresses of manufacturers, prices, fcc, we are obliged to consign to the Sixpenny Sale Column. Thev are only of interest to the party who asks them, and take up too much valuable space. Your query is one of these.

James Gouoh.—We discourage private communication.. Put your query in another form and it shall appear.

L. H. Widdowson—Many thanks for your replies. You are, however, a little behindhand in sending them, and aa the queries have already been similarly answered we art unable to insert your replies.

G. P. Ftb.—First query cannot appear except in the Sale Column. Srcond query has been answered very recently.

W. Fi.UEES.-Why write to us when you know the author's address I The contributor you nam. wiM probably again appear shortly in these columns.

P. A. Fotheeoill.—We have not received the communication you mention.

Harcourt'b Brake Chain.—R. W. Rose, of Haddcnham, buffolk, wishes us to state, "for the benefit of thase who are cautious, that he has tried the above and find, it first-rate."

Tintac—Your question on rifles would involve an answer that would ocenpv several col umns.

••■ R.—Inquire in Paternoster-row.

Geo. Da Vis —We are quite disposed to give the wides t latitude to correspondents. Dr. Bedford may certainly be left to take care of himself.

David Fisher—You know as much as we do about the 'Macclesfield " velocipede.

Thos. J. O'connor—Your reply throws uo additional light •n the poker question.

C. Wright.—Question too insignificant.

C. B. C—We should think not.

X.Y. wants to know whether we can recommend any "jobbing mechanic " to make a wor king model. The Sixpenny Sale Cilumn ia sure to bring him what he wants.

Tahtau—Thanks for promised co-operation.

A. S. C—It matters little, but all communications addressed to the Editor are sure to be attended to

T. J.O'connor -Yes, post free Is. 9d. each.

Boaz.—We cannot speak of the respectability of advertisers. Carbon filters may be had in Fleet-street, Loudon. See our advertisement scale.

H. D.—Thanks for the suggestions.

The Long Firm—We find several have been duped by Claude and Co., of Cheltenham. We have reason to believe that the same" firm," under the name of Parks and Co., hail from Abington. Next week in all probability it will assume another name in some other town. We can only say to everybody, Be on your guard.

THE INVENTOR.

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IJ0b«to» to the rent-onion, of. number of refers, wo havo deciae.1 on appropriating- • portion of our spurs to • condonsed list ol patents as noarly at possible up to the date of. our Issue.

APPLICATION'S FOR LETTEIIS PATEXT DUrtlNa THE
WEEK ENDINO M.UICI1 11, 1870.

mSehtaesJ' ^ <""' "' L*rch1''' •'• K'»*'« Cross-road, reaping

«?«. J. Plosrome, Plalstow, rolls for railways. d4ln',m^hi,n'in*r,1S"1"t S""hto'"-1""'. London, cntrlfuE.1 .»^ln^,?d.uM"tg00rtOD' °- H"r'"°°' J' W*nU"' « L>1»h' for8b„rU;g-Ae?oSu„le.i.".*1*m0r6-,,,"M' P',Ckh"n- "*"TMtu"

«u Il'r^l^lffi.B'1 f"1"^ '■*■ """ OT""tTM='i°>> of tapping-cock. S' O II mil ~ '& I,»l>r"vom.ot.ln treatlnj arain. S?.' w 7.' . n m^W ««bnry-on-seeorn, TM'i«r skin diseases. meters. """"loaon and J. Ssndibmcls, Edinburgh, dry gas

6"6. J. L. Norton, Bolte Ssnvairo-ysrd, looms, Si' ■k L^T. «f Cockaptir-street, fire ormi.

wJISr °" rre*I<m ""i J- i'r«"1»«. D'Ptford, preventing waste of

Ml' W 1Kr^'.h^°' °L,0^h"Ter °r">H°- »»v Lewes, bleyele.. ~mn.mde.tu" '"»■ ^ c"»°<*nr-Uno. motive-power .ufbaea, A 69S. J. Kopklnson, of Sonthrort, furni.ee and boiler

I'i.-:... i ..'i.Tiuit l)„....l. ,.i L,

So?' ?,T5'i"!r' J,:i"b"wiek, Bough, bleaching.
691. J. Duffej, Chelwwi, proteetlon from fire.
<m. T. 8. Truss, 434. eld Kent-rosd, boilers.
*?%• ,; N.,,ll8.on. dlssgow, cast-iron cooalug utensils.
I.'.'7. ',. lowW-r, Raaford. smelting; iron ore «

Sf.' uS Wn«'a: Liverpool, mlll.tono picks.
SS' w STM?' P*11:' b'nding of cut crops into sheaves.
comLnicLuon '' ^lt'^""-^'^'. London. etehing.-A

,',»'• A*',," L*^°' t,hSw.H1'!? machines -A communication.
T """"O-1 »■■'•;»- "•». "agloy, dulling thr.a.1, or yarn,.
/S3. T. Ncwnton, Msnchenter. lire-arms j-*—.

7«. tt. BUkeboroujh, Brighou^ and S. Sanderson, Huddorsneld oon-uniptlon of smoke. """otsueiti,

7i1j. II. L. Glbunn, Liverpool, hats.

?mCT' i; 'y,'"'1"''' Sh",'leld- ">»wlng and forcing fluids.
Im r' n' ro"r. \vlc""-l» Chambers, rolling stock of railways.
70S. J. Brady, Maucheiter, skirts »au-»

vv!' i' n' T*,1TM- H*r."orf • di"*i"atton of crude petroloum.
oation. Jol"Mon' Lincoln'e-Inn-flelds, wheel tiroa,-A communl-

'•'■ i- Je^vons Shcmolii. armour plates.

712. T. V*. Walker, Sandford. cnauiollinir.

I '.' ,* i.",''7' Letth, purlflcalion of icwtlc.

if ?' 5: L"ke- eitlnsTulshlnir llro.-A communication, crushing. *° Sturgeon, Bolton, machinery for

71*. 11. Henry, 6a, Fleet-street, tannins;

7S7. .1. Wallace. Belfast,dlstillini?

Hi i' *„n<l JvuJPkinTMn, Hucidersneld, Indicators.

'!.,;, n "'""-'".Kl1"-'" • npon-Dull, damper, of boilers, .wlsf^.n.'^,' jramS.1""TM""0'' C0U°" ""»««*«'. »""">«

T W'tel". Birniinvham, wateHnegnrilens. inaehini'' *"*' Lejtoustoue, and C, Thome. Mark-lane, hackllng bon?s °' A'lJ°' B-Mk[a- ""d *■■ A- Attl", Birmingham, reducing

-Jf u 1' J"hn«>n-„comllng (lax an.l hemp.-A communication.

7» ?'j.cf""1^"'.,'•i.«"kvill«..troot. setting typ,.,

l„ TG-J»;k.on Jllrmlngham. vulcanl.mg indla-rubbiv

787. J. Siddona, Wast Bromwlch, clocks. ru0°".

PATENTS BBUsO PROCEEDED WITa.

5!in' b nf*Tt' """l" Power englnoi
"J w.:Biroh, sewing machines.
3171. P. Jen-en. suns

IS' s f^r'"^ J' N"rtTM- tramway.,

3106. J. ifaUlen. lusriestors.

JSI7. T. Perkins ploughing."

Jl». 0. D. D.,l..rodd«,.*

ha"SdLJ' TrMr %ai a T~^. »»"»*URa, psru.1,, wh.pn.4^.,
*•*■ J-Ingloton. wstorclosoU

BlJSJilutaSor *°'1 Ue0rg* *«"*»>'. combing wool, aud«i«
3J1«. M. Tulhill. horsa goar
lli^- i 5Th- "°*'ln« maoMnoa.
US' « ?"!°,,,'>,k, "■ '•"bos.
Vi& W V^l1"' "'oojb-loadin, firearm..

3£6. C. H. Holt, fura.eef

l«hVivX^°i'oZ.E' T-b- -"** "-f

M91. F. Clark bricks, tiles.
3300. W. H Tucker, lockiT
«nj. W. Srlaley, motive-power

2fe I! W.^oo-^i'llng^l^' »"■»■•
if?.- ?' £• Go-x1'1! l"k bottles.
V.TM li^"""' "'""« match splints.
313SI. W. Cross, shiwl*.

aS? 7■^nL',kt' "'"Otfo-magnotlccircuits.
•JiJ. '■ B. Ooush. collar stud.
Sa' »' g-"oWarmld, sails of rijps.
soSmi. v»°4lhan. manufacture of lluorUo of potassmm .net

109. J.imosGreenshIelds,obtalninKoll
!!?' I" J- !!>"*• animal charcoal.
KK. W. T, Walto. filtering.
S05. W. Oarton, saccharine matters.
Ml. K. H. Durie. railway brakes.
JM. W. Orr. Scotch caps.

318. J. Davenport, riddle for cleansing potatoes
soa. J. Thompson, door handlos.
113. W. E. Lake, drvlne sugar.
*miv ^ Lfl°ker. horticultural stroctnres.
12a. J. Morrison, ga* stores.
133. T. Whitehead and H.W. Whitehead, spinning Hbrous suj>-

HIS" «'w^5KVFh.*arU,ff wd clipping apparatus.
wSU. s. w. Clark, lamps.

«?5' w »ulinJr'rcmr Ttn* p*'11* fr°m »«o4

Sla. W. B. AdamB. tramwayii.

•W. W. Adams, draMinic wtoofl.

e«1 ,T- ?■ Newton. apHnim for carriages.

bU. H. A. BoantT.-le, boot*.

MO. a. Rydill.purifvlnn mill waste.

Ml. H. A. Boiinevillo.fiieam e&ittntM,

064. J. H. Jonaon. ocwinij and other madiiDcs.

A78. A. Godllot. militarj t*snt.

5M. L. Sterno. wheel tyrea.

604. H. Harward.rirnfl.

63o. J. C. Morrell. naniUry apparatus.

M9. J, AUinaiin, dreaalng wheat.

Allpenoni haTin« an Interest in opporinff anr one ofeTwaapplioatiouB are at liberty te leave parUtrnlara in wrlttnjT oflhc-r objectiong to iuch appUc*tion at the aaid OlHoo of the Ca/msi;— sionera, on or before the 4th of April, 1870,

PATENTS SEALED.
2WWi. W. E. Kflwton, fnrnaoea and OTena.
MM, T. Eeatell, breech-loading flre-amii.
2603. G. Shaw, combined buckle and bnttanholc.
*707. Or. A. C. Bremme, breaking flai.
2736. A. Brooman, chains.
2743. J. I'Anaon. railway afimals.
H^i- "{• ^ R Bwi*ou »nd F Bernard, vhoes for homes.
2S13. A. E. rrldlamiiT. watches and chronomotore.
SOW. W. E. Lake, sewing machine ncedlca,
8108. W, B. Lake, sewing machine needles.
8658. J. Loader, meters.

8690. W. Galloway, joints or eonpllngs for plpoa.
146. II. B, Read, wrapping rug.

2715. T. and Vf, Wheatley, fasttulnga for carriage doors.
2780. J. Poison, grain.
2782. W. E. .edge, bed.
2738- U.Doirirr, Teloclpodos.
2784. P. Wlnlom. machine for twining hair
27fi". VT. B. Ged« drying machine.

2777. B. Hunt, railway bral

8571. J. Willi-. nmbrellas.

8709. J, Asbary. screw sp-tunors.

SH6. J. Woodward, bricks.

99. W. Goroham and L. White, Portland Cement

X13, W. Lake, reaping machine .a

PATENTS OX WHICH THE STAMP DTJTr OF 'i) rt V 5
PAID-1867.
fill. J. Marahfill, safety gauges,

660. G. H. Daw, cnrtHdges.

702. T. Burt, apparatus for mering mud.

888. H.Sharp, manufacture of iron.

Ml. H. A. BonncTine, preferring solutlonji of plants.

687- A. Kimball, Hewing machines.

7st8- P.T.Goodwin, animal charcoal.

7<«- B. P.Walker, TalTtM.

707. John F. Brlajes, animal charcoal.

T2&. e. K. A. Glorer, tackle for weighing anohora .

PATENTS ON WHICH TnE STAMP DUTY OP £100 H \S BEFv
PAID.—1867. *••***-!*

651. C. H. Lon, closing the gates of railway crossings}.

661. W. IngLut, steam tollers and engines.

AND

MIRROR OF SCIENCE AND ART.
FETO AY, APRIL 1, 1870.

A PRACTICAL TREATISE ON THE
HARMONIUM.*
Br Hermann Smith.
THIRD DIVISION.—CHAPTER I.

ОТ THE COCPLEÄS AND COUPLING MOVEMENTS.

Tmf education of the muscles to delicate manipulation i- more difficult than the acquisition by the mind * of the principles which govern it.—Waif.

THIS treatise was commenced во long ago, and suspended during so prolonged an interval, that bat for the repeated solicitations made to me personally, and in correspondence, to continue my lab.Jut. I should be justified in resigning the vocation of the teacher. My unbroken silence may nave teemed to indicate a total disregard of wishes so frequently expressed. It has not been »o. There are periods in life when circumstances arbitrate against onr inclinations; there are other periods when the turn of the tide favours our designs.

1 accept the opportunity of renewing my

acquaintance at a time when the English

Mechanic is starting on a new etage of its career

of use fulness. Many thousand new subscribers

bare been added to its circulation since my hand

was familiar in its pages, and I know of a surety

that it retains the old readers who were wont to

give me welcome. Let me hope to obtain from

all readers, both from the old and the new, the same

Vrai VoAnigeuce and consideration in the task I

now «some.

The treatise was framed to embrace the theoretical and the mechanical exposition; it is to the latter branch of the subject the first link iball be made. The amateur constructor of harmoniums ¡s seldom content with the early efforts of his ingenuity,- larger and larger his ambition grows until nothing less than a doublemanual instrument will satisfy his desires. To have »n instrument like an organ, that is ' the thought that holds him with irresistible fascination. He decides on his two manuals, and perhaps on pedals, although the probability is that theЫ1*т will be postponed until the former has been attained. Couplers are an important feature in an organ, and how to provide for these in the harnv-.nioin becomes a matter of solicitons {regard, for the coupling movements of an organ, hidden, complex, and involved in mystery, present themselves bat vaguely to his imagination, and in proportion aa th*j seem to defy his scrutiny, so his anxiety increases to ascertain the details of their construction. On no question have we found amateurs more carions than on this concerning conplers.

The modes of* adaptation to organ requirements are indeed numerous and ingenious ; it is fortunate for our laboar that in harmoniums the coupling movement Ы almost wholly restricted to one kind and two varieties. The connection to be effected is " swell to great," and it is attained in two ways which, in whatever mode they appear, «e essentially the "sticker-action" and the "»edge-actim." Utility has dictated the restriction. Large harmoniums are of necessity cramped * room; space for complicated or duplicating **û« is hardly to be found, and no good pur■r°» »oald be served by the addition of move^s*2t» capable of acting in reverse order, as F** tu swell," and "pedals to great." The ifTl тЛ^ ^"ПСУ 8nch accessories; the pracne»' fflOEcian finds he does not require them. Г** harmonium coupler is designed to give the tower manual the power of acting upon the upper manual, to combine with its own whatever power Jjj* swell or npper souDd-board may possess. Ireoerally this upper Eound-board trill have but

*T"e copyright of these papers Is reserved by the Aotaor Ttiey were commenced in 9*, and continued

fSl*!i. **■ **• ■**■ I05. к». 4*. «*. i«. iae, 132,133,

£*. Hl, 161 Ш. tee. in, 1Ь0, It», all of which are to be »ad except Ka. O*.

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one, or at most three rows of reeds; it is inferior in strength or body of tone, and is therefore held to be subsidiary to the lower sound-board. The keyboard is sometimes termed a " bank." Two manuals are two banks, one above the other. Between the two sets of superposed keys, there is a vacant space from end to end, and usually the distance from the top of the lower set of keys to the under side of the npper will be fouud to be about one inch and a quarter, or in some instances an inch and a halt'. We refer to the stem portions of the keys beyond the ivories, and beyond the key-pin rail or centre rail supporting the keys, which, for this class of instrument, are "balanced keys." The keys would be between sixteen and seventeen and half inches long, balanced at eleven and a qnarter inches from the front. Within the space under the far ends of the keys we are at liberty to arrange a coupling action.

The problem is how to provide a means of contact between upper and lower set—contact that may be made or broken at pleasure. Cut a piece of stick one inch and a quarter long, insert it between two such keys, and your contact is complete, your coupler is made. Strike the key of the lower manual, and the corresponding key of the npper manual repeats to it. Strike it again, and your stick that ought to be a sticker shirks its duty and goes off without leave. You want to provide for a certainty of action, and to be able to claim its aid or to dispense with it at pleasure, therefore a mechanical means has to be devised for the fulfilment of that end.

Simple as the requisition is in the form we have expressed it in, the mechanism that will fulfil all your demands is equally simple. Contemplated in this way there is no mystery or perplexity; knowing exactly what you have to do, how to do it is a easy problem. A "sticker" or a " wedge" will do it, these are the two forms. A sticker is a little rod, it is fitted to slide with upward movement through a perforated bar. A wedge is a little block of tapered wood fitted also to slide horizontally between projections fixed on the key-stems. Notice the distinction: In Fig. 1 we have the sticker coupler, in Fig. 2 the wedge coupler.

In Fig. 3, the same sticker coupler shown out of gear; in Fig. 4, the wedge coupler out of gear. The lettering in Fig. 1 indicates—A, the key-frame of the "great" or lower manual; C, the key-frame qi upper manual ; B, the blockframe intervening; D, the swell sound-board.

Of these we decidedly give the preference to the latter, because it may be drawn into action at any moment without risk of dnmage. The sticker movement is much more liable to derangement, if drawn on suddenly when the hands are on the keys. The action being of a rotating kind, such stickers as come in contact with the ends of elevated key-stems are in danger of being broken. The wedge motion being a horizontal one, no such harm can happen under any circumstances if the framework is properly made and accurately adjusted. In some instances we hare so great a depth between one portion of the key or stemwork of the harmonium and other portions with j which we desire to make contact, that it becomes ( advisable to combine bjth wedge and sticker coupler; these conditions can arise only undci j some peculiarities of construction, and then to accomplish our purpose we make the sticker a I

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fixture upon the stem, with the wedge working above it. v

In the proper shaping, fitting, and arrange, ment of coupling movements, great delicacy of manipulation is required. It is of the utmost consequence that there should be no difference in the depression of the keys moving under the coupling action, and the depression given to the same keys by the fingers. Unless this nicety of adjustment is cared for, the pitch of the notes will vary, and the instrument will always be out of strict tune whenever the couplers are in use. Between any two sets of keys certain inequalities will always be found to exist as to depth of space to be filled under each key; if the wedges or stickers are all cut to one pattern, nil will not be equally effective, therefore such inequalities will have to be made up by the requisite thicknesses of loather.

The construction of the sticker action is in this wise :—Take a piece of hard wood of the length of the inside of the key-frame, shape it into the form shown, which is that b;st adapted for strength. On one ridge mark off spaces corresponding to those of the ends of the keystems, drill sixty-one holes of about quarter inoh diameter, bush or line these holes with fine cloth, and fit them with stickers of suitable length. Find the proper position for the working of this bar, which should be as far as possible from the key-pin rail, in order to obtain such an elevation or throw as will most nearly correspond with the depth of finger-touch at the ivory end of the keys of the upper row. Should the stickers strike the under side of keys too near to the key-pin rail, the difference of leverage would be objectionable, and perhaps cause the elevation of the key on its pin To obviate this error you will keep the swing bar ar far as possible backward, or else will have to leave the stickers with an extent of play prejudicial to the quick repetition of the keys.

Pivot the swing bar within the key-frame in any suitable manner, and so adjust it in connection with the stop-rod action, that it may be rotated a quarter of a turn, and at each end a spring should be placed to return the bar out of gear. The stickers, when in gear, will be in upright position, and when thrown out of gear will be in a slanting position, inclined at an angle of about 16 degrees, when the movement of the keys either above or below will not affect them. The stop-rod action for the sticker plan of coupling is best placed at end of keyboard. To prevent noise or rattling in the working, the keystems should be faced with cloth or leather at the parts where the stickers would touch them. Probably this operation may be dispensed with if the stickers are light or are held by the "bushing," because there is the objection that the leuther or cloth may be roughed up by constant wear, unless very carefully fittod. The points of stickers should also be nicely rounded, and to prevent the stickers falling out of the bar, it is necessary to drive little sprigs of wire into the sides, allowing only the play sufficient for the dee performance of their duties.

With attention to these particulars the success •fa sticker coupling movement thus constructed will depend on your own accuracy of work and skill in adjustment

Whenever there is room in the instrument it will be desirable to adopt the wedge form for the

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coupling. Make a rectangular frame very firm and light, so fitted in grooves made in or attached to the upper key frame, that it will slide back wards and forwards to the extent of an inch, more or less. As to exact measures you will be guided by circumstances, variations will not effect the method pursued nor the plan of construction.

Supposing the lower key-stem rises in its throw a quarter of an inch at the portion for Contact of coupler—probably it will bo less than that—it is clear that you can occupy all the depth or space between lower and upper keys excepting that quarter of an inch, without interfering with the proper movement of the keys; but if you fill that quarter inch with a wedge the keys will be in contact. It is not needful for Ub to draw quite so fine a limit. Enough if you understand the calculations to effect yourpurpose. On every keyBtem glue projections of wood shaped as shown, those above and below will meet within a quarter of an inch or so, and your wedges at the thickest part should be of a thickness that will fill that

polarity is induced in it, and the attraction results from that process, but on removal from the inducing magnet, the iron returns almost entirely to its previous inert or unpolarised state. Steel, on the other hand, is much less strongly attracted, but retains the polar state; both circumstances resulting from a resistance in the molecules to an alteration in their state. This, no doubt, IB connected with the fact that steel is a compound of carbon and iron, and thus its molecules are very different from those composed of two atoms of iron only. This resistance is termed the coercive force of steel, which varies very much in different samples. Those in which the coercive force is greatest are the hardest to magnetise, but make the strongest and most permanent magnets. This property, therefore, furnishes a limit to the magnetism any steel can possess, and is called its point of saturation; temporary power may be given beyond this, but will speedily be lost. Another element in the power of its magnet is the force of the source from

apace and produce contact the moment a key on wnjcn it was derived; thus, if magnetised from

lower manual is struck. These wedges, 61 in number, should be covered with a clean firm leather, fitting them to slide easily, the smooth or grain surface outwards; leave a tail of leather, or better still, of parchment, by which to affix the wedges to the front rail of your rectangular frame, each will then have free movement, held by a firm hinge of parchment. On your frame, screw a strip of hard wood bevelled inward, covering with it all the parchment hinges, and bearing up that the points of the wedges may, as it were, have foothold during the moment that the action returns them out of gear, because at the first instant of the start, some may be held under pressure, in event of the hands being on the keys. We have called these little blocks wedges, but when all properly arranged, symmetrically inline, they appear like a row of pianoforte hammers; ■ and it covered with scarlet leather, will look highly ornamental when the instrument is opened for examination. If the Harmonium affords ample room, these wedges or hammers may work . on an action rail as stems do, be of larger size, and with wire pivots instead of parchment hinges. So also it is perfectly immaterial whether the thin ends of the wedges are turned to front or back, whether the couplers are thrown into gear by a forward or a backward movement. As a rule we should predict that you will have to work in close quarters, with not an eighth of an inch to spare; and then it will be found that practically it will be best that to " bring into gear," the action should throw the frame forward, and have springs at each end of frame to "return out of gear" promptly; and check-blocks to determine accurately the traversing distance to be allowed in the backward and in the forward movement of the frame. The stop-rod action for (his coupling movement we should desire to place ate near centre of keyboard as can conveniently be arranged. The devices of leverage suitable for the purpose in relation to the stop-rod are be obvious that it were needless to present further description or illustration. Methods to be adopted for pedal coupling will be described in chapters connected with other particulars of the pedal harmonium.

(To be continued.)

another magnet, its force cannot exceed that of the magnet used: that is to say, its relative molecular force in proportion to weight ; hence powerful magnets should be employed to impart the force.

90. MAGirETisATioir.—Steel may have magnetic power developed in it by drawing a bar magnet along its several surfaces, always in one direction, or the same process may be adopted with a horseshoe magnet; in both cases it Ib still better to arrange a complete system of oars forming an octagon or square, and draw the magnet round and round, always in one direction j in this plan the bars may be all steel, or alternate steel and iron.

If the operator has two bar magnets, an excellent plan is to place them with opposite poles together Over the middle of the bar to be magnetised, and then to draw them slowly asunder to the ends, repeating this six or eight times on each face. This process is still more effective if the ends of the bar rest on two other magnetic bars with their opposed poles in the same direction as the moving magnets. Pig. 32

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EXECTRICITYAND

88.

ITS THEORY, SOURCES,
APPLICATION.

By J. T. SrEAotrB.*
(Continued from page G22, Vol. X.)
By means of electrical currents, which
consist of energetic polarisation of
the molecules of the bodies they traverse,
and which induce similar and parallel lines
of polarisation in all surrounding bodies, mag-
netic effects can be developed in all substances,
and Faraday and others, by means of very
powerful magnets, have proved that magnetic
actions do thus occur, modified by the nature
of the substances and their molecular arrange-
ment, which lead to a classification of substances,
as magnetic and diamagnetic. Iron is the most
highly magnetic substance known, then nickel
and cobalt, but the first alone has any particular
interest for us.
89. Whenever iron is melted, magnetic

shows this process, n 8 being the bar to be magnetised and W a piece of wood to support it and steady the lower magnets. This is called the method of single touch, and is best suited to thin needles and bars, not more than a quarter inch in thickness.

The method of double touch may be illustrated by the same figure. The triangular space between the two movable magnets is filled with a piece of wood, and their upper ends connected by a bar of soft iron, and both are moved to and fro along the bar W *, without separation. This process gives more magnetic power than the other, but it is apt to be irregular, and to produce consequent points— that is to say, reversals of magnetic polarity within the bar.

In magnetising steel in the horse-shoe form, two should be placed with their ends together, and the magnets carried round the system, or if two are not needed, the ends should be closed with an iron armature.

THE Battery Process.—Thisis the most effec ■ tive, and willdevelop the greatest power—needles may be magnetised by enclosing them in a helix extending their whole length and passing a strong current for a few minutes; for large bars and

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horseshoes the instrument Fig. 33, is well suited. It is simply a short helix of stout covered wire,

the central opening of which is large enough to allow it to be passed over the bar. It should be arranged at the middle of the bar, and connected to a battery, sending a powerful current through it, and regularly passed along the length both ways several times, allowing the ends to half enter the helix, and brought back to the middle before the current is stopped, and the action is facilitated by slightly tapping the magnet during the process to produce vibration. The laws of this process will be explained under the head of electromagnetism.

91. Qcality Op Steel, And Temper.—For large magnets, hardened cast steel is best; for compound horse-shoe magnets, the same steel annealed at 500°, or hard shear steel ; for needles, cast-steel annealed in boiling oil. Steel made of the best iron, such as Swedish, makes the best magnets, and the hardening or tempering should be equal throughout.

92. Form And Arrangement.—For compass needles, the best form is B flat, tapering from the middle to the points; for bar and horseshoe magnets, the mass of material should be divided into a number of plates not exceeding a quarter inch in thickness, separately tempered and magnetised, and arranged with their similar poles together; they should be insulated from each other by sheet brass, or cardboard, and bound together either by Bcrews or external bands ot brass. The ends should not be flat, but tapering, so as to concentrate the action on small terminal surfaces; and in some cases, it is well to terminate the whole by pieces of very pure soft iron, shaped as desired, fitted to the end of the bars, and secured to them.

93. When the number of bars are thus united, the total force is never equal to the sum of the whole, separately, because thesimilarpolestcndto neutralise each other; in some cases, the central bars will even be reversed by this action, for which reason they should be the longest. This is the reason, together with the superior temper of the surfaces, that a number of separate pieces give more power than to solid bar of the Same mass, as in this the interior portions are apt to take reverse magnetism to the exterior, thus corn- pleting closed magnetic circuits, and leaving little force to be exerted on external objects.

94. Preservation Op Mao-nets.—They should be carefully handled, and all jarring actions avoided ; when not in use, needles should be placed in the true magnetic direction, and with their south ends raised to an angle equal to the latitude of the locality ; the same with bars -, but either may be still better preserved by placing two together with their poles reversed, and a small piece of soft iron between them at each

nd. Horse shoes should always have the keeper or armature on, and their powers may be greatly increased by hanging them up with B weight attached, which can be gradually increased. Care should be taken, however, never to violently detach the keeper, and when this is removed for use, it should be done by sliding it off across the poles, not by pulling it away.

95. The Directive Force.—Amagnetcapable of free motion, if approached by another magnet, is attracted by this, if extremities of opposite names are nearest, and the ends of similar names repel each other. This repulsion, however, like that of electricity, is only apparent; it is the consequence of the fundamental principle of magnetism, the polarity of the molecules. It is simply the effort of these molecules to place themselves in the parallel and consecutive order described in section 87. In soft iron this is effected by molecularTeversal; the coercive force of steel resists this, and therefore the mass of the magnet tends to turn round to effect the same result, and if this be resisted the molecular action very commonly occurs, resulting in the permanent weakening of the magnetism, or even in the total reversal of that of the magnet whose intensity is least. The • direction in which the free needle will arrange itself depends on the positions and distances—in fact, it ranges itself on the lines of the magnetic force of the fixed magne1, viz., en the curves shown in Fig. 29, and the apparent repulsion as well as attraction are due, not simply to the visible bodies or magnets, but to these lines of force or chains of polarized particles of air, &c, which snrronnd them to a considerable distance. This is very distinctly shown by the process of attraction upon iron. If a piece of soft iron ia applied to the N. end of a bar magnet, it is attracted because polarity is induced in it; it becomes itself a magnet with its S. end in contact with the magnet. If, now, a second bar magnet .is applied with ita S. end to the other end of the iron, the action is increased, the iron held with double force; but if the N. end of this aeeond bar be applied, the two actions neutralise each other, and the iron, though in contact with two magnets, nill have no attraction exerted upon it.

96. The earth itael facto as lb large magnet, and hence a free magnet arranges itself in relation to the magnetic poles of the earth, which are not at the same points as the true poles of its axis of revolution, nor are they even permanently fixed. The consequence is that the compass does not point true Northand South, nor exactly in the same direction at all times. So also it does not rest in the horizontal direction, but in the Northern hemisphere, with its N. pole lowest, or dipping, pointing to the magnetic pole, and thus occupying the magnetic curves of the earth in a manner exactly similar to the behaviour of u suspended magnetic needle in relation to a large bar magnet. Terrestrial magnetism ia a subject by itself, and one of vast practical interest, but it is out of the scope of these papers. Our concern with it is simply to regard the earth as a huge magnet, and to see, where necessary, that its actions are the same as those of any other magnet, and to see if the probable causes of its magnetism aid us in studying electricity.

97. Ampme's Theory.—As before remarked, magnetism was formerly explained by the invention of two fluids; but the theory now universally received is that of Ampere, which, though properly belonging to electro magnetism, it is necessary to touch on here to complete the explanation given in Section 87. Working from the fact that a circular electrical current constitutes a magnet at right angles to its plane, and that electro magnets are practically composed of a aeries of Bush circular currents ranged in the form of helices, and also from the fact that the force is evidently possessed completely by the molecules of permanent magnets, he taught that magnetite substances are composed of molecules around which currents of electricity are constantly flowing; that magnetism consists in ranging all these currents in parallel order, and it has been thoroughly proved by the moat stringent mathematical analysis, that this beautiful idea explains all the facts of magnetism. Fig. 31 exhibits

steps at once into the position mathematically proved true, but avoids these objections. It replaces the molecules with their separate circulating currents, by molenulee in a static polarised condition. Fig. 35 shows at once the resem

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n, showing the sup posed molecular currents, the Bum of which acts like an external current, and B represents a cylindrical magnet, of which A ia the end shown, or any section looked at from that end.

98. But beautifully scientific as this theory is,

there are fatal objections" to it, not generally

seen. In tbe first place, it is based on the idea of

eleetrieity bein^ an entity, a something which can

oreoUte round the molecules in a real stream, and

thwelore it in inconsistent with more recent views

as to the nature of electricity; but apart from

this, though we might assume it to be possible

that such circulating currents might be confined

to the molecules, it is impossible to conceive how

they fail to arrange themselves symmetrically

always, or why once arranged, as in magnetised

iron, they derange themselves at once the moment

the inducing magnet is withdrawn. The very

nature of electric currectswould require a coercive

force to prevent the magnetic condition being

always existent, whereas the reverse is the fact.

99. The molecular theory, or rather that modification of it which I am setting forth iu these papers, takes possession of all Ampere's work,

balance and the difference in the two theories. A, regarded as a permanent magnet, shows the molecules retained as a polarised chain, analogous to the conditions of static electricity, and it shows how an electric current generates this state in lb bar around which it circulates. The coercive force of the magnet is due to the resistance of the molecules to the change of condition, either to being magnetized or demagnetised in the case of steel, the molecules of which are compound, while iron has little power to resist either. What it is in the molecules of iron and steel which given them these properties, we do not know.

loo. Lawso* Magnetic Foece. Many attempts have been made to fix the laws of attractive force of magnets, and the result appears to be that it varies inversely as the square or the distance, as it must indeed from the cause w universal law of actions proceeding from a centre, as it is a necessary consequence of the fact that the areas of spheres increase in that ratio; but this only applies to each point of a magnet regarded by itself; practically no distinct law can be laid down, as the force is R compound action and varies with the form of the magnet. Thus the p dee of a magnet are the centres of action of each half of the magnet, not necessarily the points where attraction is strongest, which is usually at the end, while the poles are generally at about two thirds the distance from the centre to the ends, and in tapering needles, still nearer to the centre. As to the attractive force or weight-supporting power, thia rariea with the quality of the steel and also with its form, length being the chief element in this latter, but this and all other details of magnetism will behest studied under the head of electro magnetism, which must be preceded by that of current electricity and its sources, to which we shall now pass. (N be continued.)

PLATINISED LOOKING-GLASSES.*
By C. WroEMANN.

NO. II.

rT^HE glass being prepared by the usual method

JL is shaped, polished and cleansed. The Platinised Glass Works, at Wailly-sur-Aisne (France), where this new industry is carried on, possesses highly improved polishing tables, so much so that the polishing operation occupies only three hours. At the St. Gobain Works this operation requires a manipulation of 48 hoars.

After the cleaning operation the glass is carried into the platinising shop, and the composition giving the metallisation is applied to the glass by means of a brush; tbe plate is placed vertically and reoeivea the platinising liquid to B convenient thickneaa. It is first, applied from bottom to top, then from left to right, and at last from right to left; by these means the oily coating ia equalised. This composition, containing a large quantity of essence of lavender, spreads itself instantly over the surface, drying slowly and without any running. Great care must be taken to avoid all dampness and dust; dampness would crisp and wrinkle the surface, and the dust would destroy the regularity of the work, as every grain of dust

absorbs liquids concentrically, and thus deprives the surrounding parts. ,

The platinising composition needs nothing else to be perfect than great cleanliness on the part of the operator.

In making the platinising liquid the following materials are used: 100 grammes carefully laminated platina in very thin sheets are taken. It is shaped, in order to remove all the grease that might have accumulated during the laminating operation. It is then dissolved in an aqna-regia, composed of 400 grammes nitric acid for 1000 grammes pure hydrochloric acid. It is heated by means of a sand bath to dryness, care being taken not to decompose the ohloride by excessive heat. It is then crushed in a porcelain or glass mortar, and laid on a grinding glass plate, where it is mixed with small quantities at a time of essence of lavender (rectified), care being taken not to work at too high temperature or the reaction would take place on this glass plate. Having added about 1400 grammes of essence of lavender, the mixture is collected in the porcelain dish and left to itself for eight days without the least disturbance. The liquid is next decanted, filtered, and left again for six days, and this filtered liquid must then be about 5° at the acid test Baumc. For the above quantity, 25 grammes litharge and 25 grammes barate of lead are taken, and. ground to an impalpable powder, with 8 to 10 grammes essence of lavender. This last mixture is then added and stirred with the platinising liquid. It is then applied as above described, care being always taken to avoid dampness and dust.

Ae eoon as the glass plate to be platinised has received the metallic coat and is aufliciently dry, it is placed in muffles, formed of a frame of cast iron, tongued and grooved, and the parts of which slide in each other.

The fireplace is placed at the back of the oven, which arrangement gives free access to the door, through which the glass is placed in the oven. Movable framea are placed in the caathioh generates "this iiron frame- ond receive the glasses to be heated, maintaining them in lb parallel and vertical position. Hooks, properly constructed, support a large number of these frames. Also, movable sheets allow glasses of different sizes to be placed in these frames.

The vertical and longitudinal section of the oven is a long parallelogram, and its cross section is a square. The cooking is regular; and the accidents of fire are regulated by registers or iron gates in the posterior and anterior part of the oven. A series of muffles are placed under the dome.

The platinised mirror thus obtained is of great solidity, and no metal is more resistant to the influence of atmospheric agents. Even when a mirror is thrown into B great fire, at the temperature at which the glass melts, it will have retained its metallic surface. The mirrors do not give false tints to coloured objects, as the common mercury alloy does.

The reflection being obtained by the anterior surface, there exists no double reflection; but what is still more remarkable is that the substitution of platina for tin and mercury is that it allows any kind of glass to be transformed into a mirror. The nitrous matter is polished on one face only, and having been submitted to the platinising proceas refleota images without distortion from the surface of the metal itself.

Let us now come to the actual process in use; the following conditions had to be filled:

After having suppressed the use of mercury, the glass was to be perfectly colourless and deprived of every defect. The oost had to be reduced, or the old routine would not give place to progress. Not only has Dode suppressed the nse of meroury, but he has by his improvement been able to make better mirrors, for he hides by his process the faults in the glass plates, and obviates half the work of planing and polishing. In order to obtain this result it was necessary to apply the reflecting surface on the front of the glass plate, and not at the posterior surface.

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MECHANICAL MOVEMENTS.*
(Continued from page 5.)

No. 1. Apparatus for disengaging the eccentric rod from the valve-gear. By ullin up the spring handle below until it catches in th,,

'Extracted trom a compilation by Mr. H. J. IJruwu i Editor of the American Artisan.

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