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[2257.)-PAPER NEGATIVES.-I should feel much obliged by "Mus" giving me some information as to aking large paper negatives. I have a 6in. aplanatic lens by Grubb. I have worked waxed paper, plain paper, and paper saturated by liquid paraffin. I can get very good results by these methods, especially for pictures 30in. x 22in,, but what I wish for is to know some method and an easy one of getting the negative 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 some good pictures from good waxed paper nearly up to the mark of the sharpest collodion picture, but I facny improvements can be made in this direction if "Mus" or the photographers which read our journal were to experiment. URfortunately. I have no time to spare to do so, but should be glad of anyone's experience in this matter. -GILLER.

(2258.]—EQUATIONS. On p. 640 of 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, and shall be thankful for any help
towards arriving at any easy solution. I have not the

least idea what room the working may occupy :-
x-a ข b

[2240.-BLACK LEAD.-How can I make black lead into small blocks, same as Nixey's?—W. S. H. [2441)-SWEET GUM. What gum is called sweet Solve (1) gum in the United States ?-C. D. P.

+

= 0

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2+ y

x-y-a

(2)

+

= 0

a

Solve (1)
(2)

(a + h) x + (b − h) y = c
(b + k) x + (ak) y = c

[2242]-TO" M. P. S."-Thanks for reply relative to digitalin I observe the formula you quote is in half quantities of the process given in one edition of the B. P. I have been considering, and have come to the conclusion that I must have been wrong in the acetic seid treatment. The words in formula are, treat the extract with 5oz. of water acidulated with the acetic acid. Now, not any special acid or mode of treatment D. E. WILLIAMS, Pontardawe, Swansea. being stated, I used glacial acetic acid in 5oz of. distilled water made pretty warm; this, I conclude, is the cause of the whole uniting into a homogeneous mass. Ought it to have been a weaker acid, and the extract treated cold? Is there any work on the above compounds?-for most of the chemical and pharmaceutical works which I am acquainted with contain but very little relative to this important class of bodies, even "Miller's Elements of Chemistry." part 3, embrace but a small quantity of them.-PHARMACEU

TICAL STUDENT.

(2243)-CONSTRUCTING FERN CASE-Will any subscriber oblige by giving plain and simple instruc tions how to make the above?-FERN LOVER.

[2244.)-REFRACTING TELESCOPE.-I propose constructing an achromatic telescope 18ft. Sin. focal length; the glass I propose using will require the crown lense te be 6ft. 10in. focal length, to correct the chromatic aberration. Will our learned friend "F.R.A.S." give me a set of curves for this combination? If any other gentleman would furnish a set of curves also, it would be esteemed a favour.-NEP

TUNE.

[2245.]-TIN SOLDER FOR GLASS-Can any reader inform me how to cause tin solder to adhere to glass, as I often see glass brooches soldered on the back ?-G. GERRY.

[2246.-STEAM WHISTLE-Can any friend tell me the way to make a steam whistle for a small model engine? A diagram would oblige.-G. GERREY. [2247.)-TICKET WRITING.-Will any of your readers inform me as to what compounds and what quantities are used by ticket writers to make black iak, also what for red ink?-T. W.

(22481-SPEED OF AIR AND STEAM-How can I calculate the 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?-CENTRIFUGAL FORCE.

(22491-NUT SHAPING IN THE LATHE.-Would "W. H N." be kind enough to answer me one question? By what means is the nose-piece fixed (for carrying the nuts) to the end of the spindle that passes through the square boss, or if the thing is of solid

steel?-CENTRIFUGAL FORCE.

[2250-THE EAST WIND--Can any of your readers inform me if it has ever been satisfactorily proved that the unpleasant quality of the east wind is due to anything beside its dryness and coldness say, to electrical conditions of the atmosphere during its prevalence? What is the best way of counter acting its influence within doors? Can some one refer me to any hook containing a record of the temperature and prevailing winds of this country for the last century ?-SAEPE.

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WORKING MEN'S COLLEGE.-The spring term of the Working Men's College has just commenced. Elementary and advanced classes were formed in arithmetic, algebra, geometry, book-keeping, English, French, German, Latin, and Greek grammar and literature, English history, the use of the microscope, astronomy, physiology, music, and drawing.

IRON CHIMNEYS.-A wrought-iron chimney 196ft. high and 6ft 7in. in diameter has just heen erected in Pittsburg. Another is to be put up 275ft. high. The first was rivetted together in a horizontal position, and then lifted to the rerpendicular by a crane. The other will be made upright; the plates will be rivetted by means of a scaffolding running up inside.

A NOVELTY IN BUTTER MAKING-A singular method of making butter has recently come into rather extensive use in France, based upon the fact that cream is changed into butter by being simply buried in the earth. The theory of this result, says the Grocer, is not very intelligible, though the fact is stated to be beyond question; and iu Normandy and other parts of France, butter is prepared on a large scale this way. The process consists in placing the cream in a linen bag of moderate thickness, which is carefully closed; then burying the bag about a foot and a half deep in the earth, and allowing it to remain from 24 to 25 hours. After the expiration of this period, the cream is found to have become hard, and it is then broken up by means of a wooden beater into small pieces, and sufficient water poured in to wash out the buttermilk. To prevent any 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 is said that butter thus prepared is of a more excellent quality.

A FLOATING TELEGRAPH STATION.-In a few days a telegraphic station vessel will be moored by the International Mid-Channel Telegraph Company at the entrance to the English Channel, in from 55 to 50 fathoms of water, in latitude 49 deg 20 min. 30 sec. N., longitude 6 deg 17 sec. W. of Greenwich. The vessel will be painted b'ack, with the words "Telegraph ship" in white letters on her sides; she will have three masts. At the top of the mainmast a large [2251.) RENDERING BONE SEMI-TRANS-black cone will be hoisted during daytime, and a powerPARENT-Can any fellow reader kindly inform me ul globular light at night, elevated 3 ft. above the how to render bone semi-transparent as we see it in sea, which in clear weather should be seen from a disimitation of amber upon tobacco pipe stems?-AMBER tance of 6 miles. A flare-up light will be shown every 15 minutes during the night from an hour after sunset 1251-DISPENSING QUERY.-Can one of our M. to an hour before sunrise. During foggy weather, day or A. P. S.'s tell me how to make a perfectly clear or night, a bell will be rung continuon ly for half a mixture of pepsine porci, 28gr.; acid. muriat. 12scru.; minute every qu rter of an hour; and for the first six aque ad, idr.—A. P. S. months, or until the 1st day of October, 1870, a gun will be fired every quarter of an hour, and after that date every hour. The commercial code of signals for the use of all nations will be used on board, to the exclusion of all other codes, and none other can be noticed.

TIP.

YACHT BUILDING-Will some brother reader give the name of a book on yacht building which gives drawings of models to scale for small yachts about 5 tons or so ?-STEERSMAN.

(2254)-DOORS.-Will walnut timber require much seasoning before using, and if it is a kind of timber adapted for doors, &e, and if the labour of working it is equal the price of oak?-SHRINKAGE. (2255-IRON CISTERNS.-What number of bolts would it require for bolting flanges together in 12in. length, and also the weight of red lead putty per foot run, or is it usual to allow so much per ewt. the cistern weighs of each kind respectively ?-FITTER. (2256.)-CLEANSING CASKS.-I have a number of empty beef barrels. The salt from the pickle has saturated the staves, and when wet weather comes the aaks become damp or sweat-some of the casks smell bal. Can someone inform me how to cure these evils? The casks are to be rebilled with liquid.-W. EBUB.

MORTAR-The disadvantages arising from those kinds of mortar at present in use are chiefly owing to inferior and being used, and the great difficulty of obtaining sand at a inoderate price. A material has been invented which does away with these difficulties, for when used it requires only to be mixed with water. In order to make one tun of this mortar, the following substances should be ground by machinery: 288lb, of lime (either caustic or the hydrate, 17281b. of slag, and 2241b. of calcined coal-shale clay. These material having been ground to the degree of fineness required, are mixed, and are ready for use From the nature of the substances used, there would be, doubtless, a more rapid chemical action than that which takes place in ordinary mortar. For plastering purposes the compost seems to be eminently suitable.

TIN IN CALIFORNIA. -The Chief of the Cabinet

of Practical Geology and Mining of the United States General Land Office, bas very recently written a letter stating that additional information in reference to the discoveries of tin in San Jacincto, San Bernadino county, Cal., has been received, and specimens of the ore have arrived. The analysis of an average specimen by a competent chemist and mineralogist shows that the ore contains 13:37 per cent of pure tin. The ore is intermixed with tourmaline, containing boracic acid, and with cassiterite. This combination is reported to be unusual and highly interesting, and the yield of tin is double that of the ores at the Cornwall mines.

ACTION OF MAGNETISM ON VARIOUS GASES.-M. Treve has communicated to the French Academy some remarkable results of experiments upon the action of magnetism upon the various gases. When the spark from an induction coil passes through a Geissler tube filled with hydrogen, the gas becomes luminous, having a blue tint, plainly violet at the extremities of the tube, and of a fine red colour in a capillary prolon ration. But upon placing the latter part of the apparatus between the poles of a magnet, the red instautly disappeared, giving place to a perfectly white light. In like matner oxygen, which gives a milky white light in the capillary tube, became red; nitrogen deepened its blue to a still deeper blue; the brilliant white of carbonic acid became deep blue; the blue of silicium fluoride became a bluish violet. The spectra of these luminous tubes changed when the capillary portions were subjected to the action of magnetism.

NEW METHOD OF OBTAINING GELATIN.Crude animal substances, such as the flesh, fat, skin, tendons, bones, etc., either with or without a previous treatment with lime, are treated with benzine, or some other similar hydrocarbon, 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 fats and oils is drawn off, and may be treated by any of the well-known methods for recovering the volatile hydrocarbon, which may be again used in subsequent operations. 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 141b. in England and in Holland. A fathom, 6 feet, derived A band, in from the height of a full-grown man. horse measure, is 4 inches. An Irish mile is 2240 yards; a Scotchi mile is 1,984; a German, 1,806; a Turkish, 1626. An acre is 1810 square yards 1 foot and 34 inches each way. A square mile 1760 yards each way, contains 610 acres. The human body contains 240 bones, 9 kinds of articulation or joinings, 100 cartilages or ligaments, 400 muscles or tendons, and 100 nerves besides blood, arteries, veins, &c. Potatoes planted below three feet do not vegetate; at one foot they grow thickest, and at two feet they are retarded two or three months. There are no solid rocks in the Aretie regions, owing to the severe frosts. The surface of the sea is estimated at 150,000,000 square miles, taking the whole surface of the globe at 191,000,000 square miles. Its greatest depth is supposed to be equal to the height of the highest mountain, or four miles.

CHIPS.

SPHEROLOCOMOTION.-This is a new system of transportation of goods, in cast steel hollow spheres rolling in pneumatic tubes. A process patented in America and in Europe.

SUEZ CANAL.-At an Indian Conference at the Society of Arts on the 3rd inst., the influence of the Suez Canal on trade with India was considered Dur

ing the proceedings, Mr. J. B. Smith said, India must improve her cotton cultivation by irrigation, and then she could easily produce 300lb. of cotton per acre."

TCHUANTEPEC CANAL.-The Mexican Minister of Public Works has sent a letter to the Congress of Mexico, transmitting the original project for conces sion for a ship canal through the Isthmus of Tchuantepec. Article 1 authorises the Tehuantepec Railway Company to construct that canal.

ANTIDOTE FOR PHOSPHORUS.-Dr. Andant, of Dax, France, has stated that in six cases 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 Bombax down.

CURIOUS FACT.-An Italian chemist has discovered that the animals of several shells of the Genus Dolium, Tritonium, &c., have a gland secreting free sulphuric acid.

THE ISTHMUS OF CORINTH-The concession for the Canal of the Isthmus of Corinth has been signed.

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24

ANSWERS TO CORRESPONDENTS.

ANOTHER ADVERTISER'S TESTIMONY. SIR,-Really your journal is an excellent medium for advertisements, for at a cost of about 4s., I have received as many orders as I obtained at a cost of seven guineas through another journal.

W. GYNGELL, Woodbine-cottages, Tewkesbury.

The following are the initials, &c., of letters received up to first post, Friday, the 18th of March:

RECEIVED.-J. H. T., Marine, Wm. Lewis, W. H. T., T. Thomas, W. Short, James Lee, J. Spurgeon, R. Morrison, Louis Simon, Heory Ussher, S. Turner, Tintac, J. H. T., W. Bear, A Well Wisher, T. S., T. Cooke and Sons, E. Kernan, Rev. P. W. M., E. G. P., Richard Cunliffe, W. Hewartson, P. Champs, J. W. Wetheral, W. Dolan, S. W. and Co., T. Brown, W. Matthews, A Working Man, T. J. O'C. Collins, Rev. E. Kernan, W. Hewartson, Rev. J. B., J. Charles Waghorn, W. Moor, Jun., Richard Cunliffe, Wm. Grosvenor, J. B., J. H., J. H. S., E. M. T. Tydeman, On Guard, D. Alston, Boaz, a Ursa Minoris, E. W. Streeter, John Young, R. A. Proctor, E. D. Rogers, W. Prossor, A Man of Kent, Joseph Newton, Beta, Excelsior, Arthur, Blue Ruin, Ross, Chain, J. B, Knox, B., R. B. J., J. T. Forbes, G. N. Stanley, Astronomer, B. W., Arthur Jones, Cornelius Varley, H. N. H., J. S., Castor, J. C. Shewan, W. H. P., Fortunatus, Cylinder, Iota, J. W., JÁ. Banner, Q. Q. R., Jas. Rogers, G. P, Cantab, J. W. Castle, Caution, B. C. W. Forward, C. R. H.. J. T. Sprague, A. E. B., A Young Irishman, Rivot, Belle Isle, A Subscriber, E. V. Y., R. T. S., One of the Old School, A. B. Pater, R. E. Barfoot, J. B., Glycerine, V. Glasbury, Old Coin, Salmo Poler, Wilholm, Alfred Savage, Jack Plane, C. H. W. Biggs, Edwin Pears, James Wilkins, A. Brothers, J. R., F. R. C. S., G. Firth, Amateur, Raimond Staes, Nobody, Fdwin Baker, A Delighted Subscriber, Physiologist, Henry Ussher, Vigie, T. Cooke, F. F. C., Geo. Webster, Bruin, F. Coles, L de Fontainemoreau, J. V. Frisby, W. C. and Co., H. C., D. Mason, Perry Davis, Amateur.

MARK ELLOR will oblige by sending us his address.
W. L. LANCASTER.- Consult Index published in last number.
A CONSTANT READER.-Write them for a circular or descrip-

tion.

JOSEPH GODBULL (Ipswich).-We only insert advertisements when they are paid for.

H. CROWTHER.-Try Sixpenny Sale Column.

D. E. WILLIAMS.-We do not remember either of your previous letters. Sometimes we receive so many answers to one question that it is impossible to insert them all. W. LEWIS.-Every number of our last volume contains information about telescopes.

W. FISHER. Consult our advertisement pages.

F. Q. Q-Part of your query can only appear in Sale Column. C. C.-It would be illegal, and we could not therefore give the information.

F. MARSH.-No charge whatever is made. serted a query for you.

We have in

G. M. TODD (Guelph, Ontario).-Your query is inserted.
Thanks for your kind wishes.
Canadians.
Recommend us to the

S. T. PRESTON.-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 query cannot appear (except as an adver-
tisement). It would not in all probability be answered, nor
would it interest anybody besides yourself.

so often.

W. C. NOTTS.-Answered very recently. We cannot repeat other blacking have appeared in back numbers. Recipes for harness and SUMMERHOUSE.-Many lists of varnish have been given; some very recently.

G. D.-Second query inserted.

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. P. W.-Premiums are generally paid. Salary afterwards will depend on ability.

W. FINCH.-No stamps enclosed.
ROTHERWOOD-On reference to our
lumn" in this number, you will find a communication
"Sixpenny Sale Co-
addressed to you.

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

not time.

NORTH BITCHBURN.-Can only appear in Sixpenny Sale TINKER-No charge; query is inserted in this number. Column. QUERCUS.-Must purchase indexes and search. We have R. H. HULL.-We willingly insert free of charge all queries asking for information; but those which inquire for addresses of manufacturers, prices, &c., we are obliged to consign to the Sixpenny Sale Column. They are only of interest to the party who asks them, and take up too much JAMES GOUGH.-We discourage private communications. Put valuable space. Your query is one of these. L. H. WIDDOWSON-Many thanks for your replies. your query in another form and it shall appear. are, however, a little behindhand in sending them, and as You the queries have already been similarly answered we are unable to insert your replies.

F. FORBES.-Your letter, or some parts of it, were illegibly written, end was therefore not sent to the printer's. Correspondents who write on technical matters and use technical terms cannot be too particular in their caligraphy. ROBERT CHARNLEY AND A. L.-Something soon.

J. W. WARD.-Read the letters and answers to queries which have appeared on telescopes.

J. W. D.-Consult back numbers.

8. J.-We have not time to search. Possibly the name you refer to was an assumed one.

ATHEIST.-The insertion of your letter would inevitably lead to a profitless controversy.

NOMME DE PLUME." Gitche Manito" does not wish to rub against the grain of anyone's sensibilities, as indicated by Sergius" last week, and will, therefore contribute in future under the name of "Minnehaha." One would suppose that "Gitche Manito" has read Longfellow's "Hiawatha" with unusual satisfaction.

G. P. FYK.-First query cannot appear except in the Sale W. FLUKES.- Why write to us when you know the author's Column. Second query has been answered very recently. address? The contributor you name will probably again appear shortly in these columns.

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P. A. FOTHERGILL.-We have not received the communication you mention.

HARCOURT'S BRAKE CHAIN.-R. W. Rose, of Haddenham,
Suffolk, wishes us to state, "for the benefit of those who
are cautious, that he has tried the above and finds it
first-rate."

TINTAC.-Your question on rifles would involve an answer
that would occupy several columns.
GEO. DAVIS-We are quite disposed to give the widest lati-
W. R.-Inquire in Paternoster-row.
tude to correspondents. Dr. Bedford may certainly be left to
take care of himself.

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. PAWSON.-Your request has been attended to. TYRO.-You must know that your request is an advertisement.

POOR MECHANIC.-We can't inform you.

DAVID FISHER-You know as much as we do about the
THOS. J. O'CONNOR-Your reply throws no additional light
"Macclesfield" velocipede.
on the poker question.

CHARLES REVELL.-We believe your suggestion to be impracticable. Try it, and let us know the result.

R. RUMSEY.-No stamps enclosed.

C. WRIGHT.-Question too insignificant.
C. R. C.-We should think not.

X. Y. wants to know whether we can recommend any "job-
bing mechanic" to make a wor king model. The Sixpenny
A. S. C.-It matters little, but all communications addressed
Sale Column is sure to bring him what he wants.
TAUTA U-Thanks for promised co-operation.
to the Editor are sure to be attended to.

T. J. O'CONNOR-Yes, post free 1s. 9d. each.
BOAZ.-We cannot speak of the respectability of advertisers.
Carbon filters may be had in Fleet-street, London. See our
advertisement scale.

H. D.-Thanks for the suggestions.

TURRET CLOCKS.-Sydney Maddison, who wrote a short time since on turret clocks, would oblige by sending his correct address to Mr. Lloyd, 135, Steel-house-lane, Birmingham. F. OUSMAN. Your letter came to hand. PROBLEMS. Several problems, and answers to others, are not insereed on account of the space they would occupy. VERITAS. The last letter appeared exactly as you sent it to

us.

WM. MORRIS.-Your answer is an advertisement.

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.

IN obedience to the suggestions of a number of readers, we have decided on appropriating a portion of our space to a condensed list of patents as nearly as possible up to the date of our issue.

APPLICATIONS FOR LETTERS PATENT DURING THE WEEK ENDING MARCH 14, 1870.

677. C. J. Fox and R. Larchin, 61, King's Cross-road, reaping inachines.

678. J. Piegrome, Plaistow, rails for railways.

679. G. W. Wigner, 1, Saint Swithin's-lane, London, centrifugal drying machines.

680. S. Brooks, West Gorton, G. Harrison, J. Wardle, of Leigh. spinning and doubling.

681. A. Villepigue, of 4, Maismore-place, Peckham, apparatus for boring-A communicat' on.

682 R. A. Wiffen, Rofd, new construction of tapping-cock. 683. J. Polson, Paisley, improvements in treating grain

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734. J. Brown, Gildersome, caring engines,

735. J. Dunnachie, Glenbolg, drying bricks.

736. J. Polson, Paisley, machinery for treating grain.

737. G. Tyzack, North Shields, windlasses and capstans.

738. W. Nicholson, 143, Holborn Hill, clog for roughing horses, 739. A. Du Bled, P. Chennallier, and J. Aufpret, all of Paris, holder for cartridges-A communication.

689. G. Preston and J. Prestige, Deptford, preventing waste of

water.

690. C. Wyndham, of Southover Grange, near Lewes, bicycles. 691. W. E. Newton, 66, Chancery-lane, motive-power engines. A communication.

692. J. Hopkinson, of Southport, furnace and boiler. 693. H. Potter, Fisherwick, Dough, bleaching.

694. J. Duffey, Chelsea, protection from fire.

740. J. Morris, Belfast, Jacquard apparatus.

741. W. Payne, Liverpool, furnaces.

742. G. Townsend, Wimbish, lawn edge clippers.

743. J. Glover, 46, Sekforde-street, Clerkenwell, regulating flow of air into furnaces.

744. W. R. Lake, indicating deficiency of water in steam boilers A communication.

745. S. D. McKellen, Manchester, watches.

746. J. J. Stevens, J. J. F. Stevens, and W. A. Stevens, 237, Southwark-bridge-road, signals on railways.

747. W. Arkell, Cheltenham, raising and lowering heavy bodies. 748. T. Routledge, Ford Works, near Sunderland, manufacture of paper.

695. T. S. Truss, 434, Old Kent-road, boilers. 696. J. Neilson, Glasgow, cast-iron cooking utensils, €97. G. Fowler, Basford, smelting iron ore. 698, W. O. Wilson, Liverpool, miilstone picks. 699. M. Frow, Leake, binding of cut crops into sheaves. 700, W. R Lake, Southampton-buildings, London, etching.-A 701. W. K. Lake, threshing machines-A communication. 702. O. Ormrod and R. Hall, Eagley, finishing threads or yarns. 703. T. Newnton, Manchester, fire-arms.

communication.

consumption of smoke. 704. R. Blakeborough, Brighouse, and S. Sanderson, Huddersfield,

705. H. L. Gibson, Liverpool, hats.

706. C. A. Winder, Sheffield, drawing and forcing fluids.

707. J. W. Grover, 9, Victoria Chambers, rolling stock of railways. 708. J. Brady, Manchester, skirts.

709. J. A. Tatro, Hartford, distillation of crude petroleum. 710. J. H. Johnson, Lincoln's-inn-fields, wheel tires.-A communication.

1. J. Jeavons, Sheffield, armour plates.

712. T. W. Walker, Sandford, enamelling.

713. J. J. Lundy, Leith, purification of sewage.

714. W. R. Lake, extinguishing fire.-A communication.

715. S. Chatwood, and J. Sturgeon, Bolton, machinery for crushing.

716. M. Henry, 68, Fleet-street, tanning.

717. J. Wallace, Belfast, distilling.

718. J. and J. Hopkinson, Huddersfield, indicators.

719. F. Brusch, Kingston upon-Hull, dampers of boilers.

720. G. Paley, Preston, Lancaster, Cotton Manufacturer, putting twist to rollers of frames,

721. J. Wright, Birmingham, watering gardens.

PATENTS BEING PROCEEDED WITH. 3154. L. Wray, motive power engines. 3469. W. Birch, sewing machines. 3171. P. Jensen, guns.

3180. C. E. Cawley and J. Newton, tramwAYS. 3182 S. Leoni, cooking and lighting by gas. 3183. A. Grothe, registering number of passengers. 3184. T. Wright and I. Fox, lace machines.

3189. N. W. Blanchard, substitute for curled hair. 3191. J. McDowell, aawing timber.

3205. J. Maiden, lubricators.

3207. J. Turnbull gears in steam engines.

3217. T. Perkins, ploughing.

3225. G. D. Davis, rudders,

3230. J. Tracy and H. Tracy, umbrellas, parasols, whip and other handles.

722. J. Moysey, Leytonstone, and C. Thorne, Mark-lane, hackling machinery.

3238. J. Ingleton. waterclosets.

3241. I. Battinson and George Battinson, combing wool, and other fibrous substances.

723. G. Atkin, E. Atkin, and A. A. Atkin, Birmingham, reducing bones.

724. J. H. Johnson, combing flax and hemp.-A communication. 725. H. A. Bonneville, 10, Sackville-street, setting types, 726. C. Jackson, Birmingham, vulcanising india-rubber, 727. J. Siddons, West Bromwich, clocks,

3246. M. Tuthill, horse gear.

3249. I. Nasch, sewing machines.

3257. P. Wilson, locks and latches.

3259, H. Rochatte, breech-loading fire-arms.

3269. W. E. Dobson and F, Dobson, lace machines.

3272. G. H. Hannaford, signals.

3276. C. H. Holt, furnaces.

289. F. Clarbour, and W. E, Teale, mining lamps.

3220. F. Brampton, locks,

3291. F. Clark, bricks, tiles. 3300, W. H. Tucker, locks.

3302. W. Srigley, motive-power.

8337. R. K. Miller and A. B. Herbert, pumps.

3403, F. W. Webb, rolling stock.

3407. E. F. Goodall, ink bottles.

3412. L. Mount, filling match splints,

3439. W. Cross, shawls,

3620 W. R. Lake, electro-magnetic circuits.

3717, J. B. Gough, collar stud.

3735. T. G. McDiarmid, sails of ships.

3745, E. P. H. Vaughan, manufacture of fluoride of potassium and sodium.

108. James Greenshields, obtaining oil.

203. W. T. Waite, animal charcoal.

204. W. T. Waite, filtering.

205, W. Garton, saccharine matters.

262. R. H. Durie, railway brakes.

264. W. Orr, Scotch caps.

316, J. Davenport, riddle for cleansing potatoes.

408. J. Thompson, door handles.

415. W. R. Lake, drying sugar.

419. B. Looker, horticultural structures.

422. J. Morrison. gas stoves.

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483. S. W. Clark, lamps,

505, S. Hulme, removing paint from wood.

512. W. B. Adams, tramways.

518. W. Adams, dressing stone.

523. W. E. Newton, springs for carriages,

524. H. A. Bonneville, boots.

530. G. Rydill, purifying mill waste.

541. H. A. Bonneville, steam engines.

564, J. H. Jonson, sewing and other machines.

578. A. Godilot, military tent.

599. L. Sterne, wheel tyres.

604. H. Hayward, yarns.

630. J. C. Morrell, sanitary apparatus. 649, J. Allmann, dressing wheat.

objections to such application at the said Office of the CommisAll persons having an interest in opposing any one of such op plications are at liberty to leave particulars in writing of their sioners, on or before the 4th of April, 1870.

PATENTS SEALED.

2686. W. E. Newton, furnaces and ovens.
2692, T. Restell, breech-loading fire-arms.
2693, G. Shaw, combined buckle and button hole.

2707. G. A. C. Bremme, breaking flax.

2736. A. Brooman, chains.

2742. J. I'Anson railway signals.

2755. J. F. R. Badiou and F Bernard, shoes for horses.

2819. A. E. Fridlander, watches and chronometers.

3092. W. R. Lake, sewing machine needles.

8208. W. R. Lake, sewing machine needles.

3558. J. Loader, meters,

3690. W. Galloway, joints or couplings for pipes.

146. H. B. Read, wrapping rug.

2713, T. and W. Wheatley, fastenings for carriage doors.

2730. J. Polson, grain.

2732. W. E. sedge, bed.

2733 M. Doirier, velocipedes.

2734. P. Wisdom, machine for twissing hair.

2767. W. B. Gedze, drying machine.

2777. B. Hunt, railway brake,

8571. J. Willis, umbrellas.

8709. J. Asbury, screw spanners.

3716. J. Woodward, bricks.

99. W. Goreham and L. White, Portland cement.

213. W. Lake, reaping machine.s

PATENTS ON WHICH THE STAMP DUTY OF 5) HAS
PAID-1867.

511. J. Marshall, safety gauges,

660. G. H. Daw, cartridges.

702. T. Burt, apparatus for moring mud.

888. H. Sharp, manufacture of iron.

684. H. A. Bonneville, preserving solutions of plants.
687. A. Kimball, sewing machines.

738. P.T.Goodwin, animal charcoal.

703. B. P.Walker, valves.

707. John F. Brinjes, animal charcoal.
723. F. R. A. Glover, tackle for weighing anchors.

PATENTS ON WHICH THE STAMP DUTY OF £100 HAS BEEN
PAID.-1867.

651. C. H. Len, closing the gates of railway crossings.
652. W. Inglis, steam boilers and engines.

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THIS

suspended during so prolonged an interval, that but for the repeated solicitations made to me personally, and in correspondence, to continue my labour, I should be justified in resigning the vocation of the teacher. My unbroken silence may have seemed to indicate a total disregard of wishes so frequently expressed. It has not been so. There are periods in life when circumstances arbitrate against our inclinations; there are other periods when the turn of the tide favours our designs.

I accept the opportunity of renewing my acquaintance at a time when the ENGLISH MECHANIC is starting on a new stage of its career of usefulness. Many thousand new subscribers have 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 kind indulgence and consideration in the task I

now resume.

FIG. 3

FIC. 2

FIC

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

one, or at most three rows of reeds; it is inferior
to be subsidiary to the lower sound-board. The
in strength or body of tone, and is therefore held
In the proper shaping, fitting, and arrange-
keyboard is sometimes termed a "bank." Two ment of coupling movements, great delicacy of
manuals are two banks, one above the other. Be- manipulation is required. It is of the utmost
tween the two sets of superposed keys, there is a consequence that there should be no difference in
vacant space from end to end, and usually the the depression of the keys moving under the
distance from the top of the lower set of keys to coupling action, and the depression given to the
the under side of the upper will be found to be same keys by the fingers. Unless this nicety of
about one inch and a quarter, or in some instances adjustment is cared for, the pitch of the notes
an inch and a half. We refer to the stem por-will vary, and the instrument will always be out
tions of the keys beyond the ivories, and beyond of strict tune whenever the couplers are in use.
the key-pin rail or centre rail supporting the Between any two sets of keys certain inequalities
keys, which, for this class of instrument, are will always be found to exist as to depth of space
"balanced keys." The keys would be between to be filled under each key; if the wedges or
sixteen and seventeen and half inches long, stickers are all cut to one pattern, all will not be
balanced at eleven and a quarter inches from the equally effective, therefore such inequalities will
front. Within the space under the far ends of have to be made up by the requisite thicknesses of
the keys we are at liberty to arrange a coupling leather.
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 upper 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.

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 best 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 inch 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 pre

The treatise was framed to embrace the theoretical and the mechanical exposition; it is to the latter branch of the subject the first link shall be made. The amateur constructor of harmoniums is 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 an 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 the latter will be postponed until the former has Simple as the requisition is in the form we have been attained. Couplers are an important feature expressed it in, the mechanism that will fulfil all in an organ, and how to provide for these in the your demands is equally simple. Contemplated harmonium becomes a matter of solicitous fregard, in this way there is no mystery or perplexity; for the coupling movements of an organ, hidden, knowing exactly what you have to do, how to do complex, and involved in mystery, present them- it is a easy problem. A "sticker" or a "wedge" selves but vaguely to his imagination, and in pro- will do it, these are the two forms. A sticker judicial to the quick repetition of the keys. portion as they seem to defy his scrutiny, so his is a little rod, it is fitted to slide with upward anxiety increases to ascertain the details of their movement through a perforated bar. A wedge construction. On no question have we found is a little block of tapered wood fitted also in any suitable manner, and so adjust it in amateurs more curious than on this concerning to slide horizontally between projections fixed on couplers. the key-stems. Notice the distinction: In Fig. 1 The modes of adaptation to organ requirements we have the sticker coupler, in Fig. 2 the wedge are indeed numerous and ingenious; it is fortu- coupler. nate for our labour that in harmoniums the

Pivot the swing bar within the key-frame 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 Fig. 3, the same sticker coupler shown out in upright position, and when thrown out of gear coupling movement is almost wholly restricted to of gear; in Fig. 4, the wedge coupler out of will be in a slanting position, inclined at an one kind and two varieties. The connection to be gear. The lettering in Fig. 1 indicates-A, the angle of about 45 degrees, when the movement effected is "swell to great," and it is attained in key-frame of the "great" or lower manual'; C, of the keys either above or below will not affect two ways which, in whatever mode they appear, the key-frame of upper manual; B, the block-them. The stop-rod action for the sticker plan are essentially the "sticker-action" and the frame intervening; D, the swell sound-board. of coupling is best placed at end of keyboard. To "wedge-action." Utility has dictated the restric- Of these we decidedly give the preference to the prevent noise or rattling in the working, the keytion. Large harmoniums are of necessity cramped latter, because it may be drawn into action at any stems should be faced with cloth or leather at the for room; space for complicated or duplicating moment without risk of damage. The sticker parts where the stickers would touch them. Proactions is hardly to be found, and no good pur- movement is much more liable to derangement, bably this operation may be dispensed with if the pose would be served by the addition of move- if drawn on suddenly when the hands are on the stickers are light or are held by the "bushing," ments capable of acting in reverse order, as keys. The action being of a rotating kind, such because there is the objection that the leather or great to swell," and "pedals to great." The stickers as come in contact with the ends of ele- cloth may be roughed up by constant wear, amateur may fancy such accessories; the prac- vated key-stems are in danger of being broken. unless very carefully fitted. The points of stickers tical musician finds he does not require them. The wedge motion being a horizontal one, no should also be nicely rounded, and to prevent the The harmonium coupler is designed to give the such harm can happen under any circumstances stickers falling out of the bar, it is necessary to lower manual the power of acting upon the upper if the framework is properly made and accurately drive little sprigs of wire into the sides, allowing manual, to combine with its own whatever power adjusted. In some instances we have so great a only the play sufficient for the due performance the swell or upper sound-board may possess. depth between one portion of the key or stem- of their duties. Generally this upper sound-board will have but work of the harmonium and other portions with With attention to these particulars the success which we desire to make contact, that it becomes of a sticker coupling movement thus constructed advisable to combine both wedge and sticker will depend on your own accuracy of work and coupler; these conditions can arise only under skill in adjustment. some peculiarities of construction, and then to accomplish our purpose we make the sticker a

66

The copyright of these papers is reserved by the Author. They were commenced in 94, and continued in Nos. 96, 98, 100, 105, 109, 116, 118, 124, 126, 132, 133, 136, 141, 151, 153. 166, 172, 180, 190, all of which are to be bad except No. 18.

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

S

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 position for contact of
coupler-probably it will be 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 us to draw quite
so fine a limit. Enough if you understand the
calculations to effect your purpose. On every key-
stem 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
space and produce contact the moment a key on
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 in line,
they appear like a row of pianoforte hammers;
and if 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 this
coupling movement we should desire to place as
near centre of key-board as can conveniently be
arranged. The devices of leverage suitable for
the purpose in relation to the stop-rod are so
obvious that it were needless to present further
Methods to be
description or illustration.
adopted for pedal coupling will be described in
chapters connected with other particulars of the
pedal harmonium.

(To be continued.)

It should be

polarity is induced in it, and the attraction the central opening of which is large enough to
results from that process, but on removal from allow it to be passed over the bar.
the inducing magnet, the iron returns almost arranged at the middle of the bar, and connected
entirely to its previous inert or unpolarised state. to a battery, sending a powerful current through
Steel, on the other hand, is much less strongly it, and regularly passed along the length both
attracted, but retains the polar state; both ways several times, allowing the ends to half enter
circumstances resulting from a resistance in the the helix, and brought back to the middle before
molecules to an alteration in their state. This, the current is stopped, and the action is facilitated
no doubt, is connected with the fact that steel by slightly tapping the magnet during the pro-
is a compound of carbon and iron, and thus its cess to produce vibration. The laws of this pro-
molecules are very different from those composed cess will be explained under the head of electro-
of two atoms of iron only. This resistance is magnetism.
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 a magnet is the force of the source from
which it was derived; thus, if magnetised from
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.

91. QUALITY OF 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 a flat, tapering from the middle to the points; for bar and horse-shoe 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 90. MAGNETISATION.-Steel may have magnetic other by sheet brass, or cardboard, and bound power developed in it by drawing a bar magnet together either by screws or external bands of along its several surfaces, always in one direction, brass. The ends should not be flat, but tapering, or the same process may be adopted with a horse- so as to concentrate the action on small terminal shoe magnet; in both cases it is still better surfaces; and in some cases, it is well to termito arrange a complete system of bars forming an nate the whole by pieces of very pure soft iron, octagon or square, and draw the magnet round shaped as desired, fitted to the end of the bars, and round, always in one direction; in this plan and secured to them. the bars may be all steel, or alternate steel and

iron.

93. When a number of bars are thus united, the total force is never equal to the sum of the lent plan is to place them with opposite poles neutralise each other; in some cases, the central If the operator has two bar magnets, an excel-wbole separately, because the similar poles tend to together over the middle of the bar to be bars will even be reversed by this action, for asunder to the ends, repeating this six or eight the reason, together with the superior temper of magnetised, and then to draw them slowly which reason they should be the longest. This is This process is still more the surfaces, that a number of separate pieces times on each face. effective if the ends of the bar rest on two other give more power than a solid bar of the same magnetic bars with their opposed poles in the same mass, as in this the interior portions are apt to direction as the moving magnets. Fig. 32 take reverse magnetism to the exterior, thus completing closed magnetic circuits, and leaving little force to be exerted on external objects.

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FIG. 32

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ELECTRICITY-ITS THEORY, SOURCES, points that is to say, reversals of magnetic

88.

AND APPLICATION.

By J. T. SPRAGUE.* (Continued from page 622, Vol. X.)

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.

By means of electrical currents, which consist of energetic polarisation of THE BATTERY PROCESS.-This is the most effecthe molecules of the bodies they traverse, tive, and will develop the greatest power-needles and which induce similar and parallel lines may be magnetised by enclosing them in a helix of polarisation in all surrounding bodies, mag-extending their whole length and passing a strong netic effects can be developed in all substances, current for a few minutes; for large bars and 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 arrangement, 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.

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FIG. 33

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

94. PRESERVATION OF MAGNETS.-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 end. Horse shoes should always have the keeper or armature on, and their powers may be greatly increased by hanging them up with a 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.-A magnet capable 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 în section 87. In soft iron this is effected by molecular reversal; 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 magnet, viz., on 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 polarised particles of air, &c., which surround them to a considerable distance. This is very distinctly shown by the process of attraction upon iron. If a piece of soft iron is applied to the N. end of a bar magnet, it is attracted because polarity is induced in it; it be

comes itself a magnet with its S. end in contact with the magnet. If, now, a second bar magnet is applied with its 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 second bar be applied, the two actions neutralise each other, and the iron, though in contact with two magnets, will have no attraction exerted upon it.

96. The earth itself acts as a 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 North, and South, nor exactly in the same direction at all times. So also it does not rest in a 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 a suspended magnetic needle in relation to a large bar magnet. Terrestrial magnetism is 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.

steps at once into the position mathematically absorbs liquids concentrically, and thus deprives
proved true, but avoids these objections. It re- the surrounding parts.
places the molecules with their separate circu-
lating currents, by molecules in a static polarised
condition. Fig. 35 shows at once the resem-

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blance and the difference in the two theories. A,
regarded as a permanent magnet, shows the mole-
cules retained as a polarised chain, analogous
to the conditions of static electricity, and it
shows how an electric current generates this state
in a 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 magnetised 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 gives them these properties, we do not

know.

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 soaped, in order to remove all the grease that might have accumulated during the laminating operation. It is then dissolved in an aqua-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 chloride 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 a 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 Baumé. 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.

As soon as the glass plate to be platinised has received the metallic coat and is sufficiently 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.

97. AMPERE'S THEORY.-As before remarked, magnetism was formerly explained by the invention of two fluids; but the theory now universally received is that of Ampère, 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 series of such circular currents ranged in the 100. LAWS OF MAGNETIC FORCE. Many attempts The fire-place is placed at the back of the form of helices, and also from the fact that the have been made to fix the laws of attractive force oven, which arrangement gives free access to the force is evidently possessed completely by the of magnets, and the result appears to be that it door, through which the glass is placed in the molecules of permanent magnets, he taught that varies inversely as the square of the distance, as it oven. Movable frames are placed in the castmagnetic substances are composed of molecules must indeed from the cause which generates this iron frame, and receive the glasses to be heated, around which currents of electricity are constantly universal law of actions proceeding from a maintaining them in a parallel and vertical posiflowing; that magnetism consists in ranging all centre, as it is a necessary consequence of the fact tion. Hooks, properly constructed, support a these currents in parallel order, and it has been that the areas of spheres increase in that ratio; large number of these frames. Also, movable thoroughly proved by the most stringent mathe- but this only applies to each point of a magnet sheets allow glasses of different sizes to be placed matical analysis, that this beautiful idea explains regarded by itself; practically no distinct law in these frames. all the facts of magnetism. Fig. 34 exhibits can be laid down, as the force is a compound action and varies with the form of the magnet. Thus the poles 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, this varies 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 be best 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.

B

Α

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

(To be continued.)

PLATINISED LOOKING-GLASSES.*.

BY C. WIDEMANN.

NO. II.

THE glass being prepared by the usual method
is soaped, 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 hours.

98. But beautifully scientific as this theory is, there are fatal abjections to it, not generally seen. In the first place, it is based on the idea of electricity being an entity, a something which can After the cleaning operation the glass is carried circulate round the molecules in a real stream, and into the platinising shop, and the composition therefore it is inconsistent with more recent views giving the metallisation is applied to the glass by as to the nature of electricity; but apart from means of a brush; the plate is placed vertically this, though we might assume it to be possible and receives the platinising liquid to a convenient that such circulating currents might be confined thickness. It is first applied from bottom to top, to the molecules, it is impossible to conceive how then from left to right, and at last from right to they fail to arrange themselves symmetrically left; by these means the oily coating is equalised. always, or why once arranged, as in magnetised This composition, containing a large quantity of iron, they derauge themselves at once the moment essence of lavender, spreads itself instantly over the inducing magnet is withdrawn. The very the surface, drying slowly and without any nature of electric currents would require a coercive running. Great care must be taken to avoid all force to prevent the magnetic condition being dampness and dust; dampness would crisp and always existent, whereas the reverse is the fact. wrinkle the surface, and the dust would destroy 99. The molecular theory, or rather that modi- the regularity of the work, as every grain of dust fication of it which I am setting forth in these Fro n the Scientific American. -Consnued from p. papers, takes possession of all Ampere's work, 651, Vol. X., of the ENGLISH MECHANIC.

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 A series of muffles are placed under

the oven.
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 a 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 process reflects images without distor

tion from the surface of the metal itself.

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

After having suppressed the use of mercury, the glass was to be perfectly colourless and deprived of every defect. The cost had to be reduced, or the old routine would not give place to progress. Not only has Dodé suppressed the use of mercury, 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.

MECHANICAL MOVEMENTS.*
(Continued from page 5.)

N°. Le for valve gear. By ullin
O. 1. Apparatus for disengaging the eccen-
up the spring handle beiow until it catches in the
Extracted from a compilation by Mr. H. J. Brown
Editor of the American Artisan.

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