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(SM5J—ORGANS.—Will the w Harmonious IHackPinith,** M Adept," or any of your organised body of contributor)) give me some information on the following subject:—When my organ was buLIt some years since, funds being rather low, about six or seven of the bottom keys in the swell were left minus any pipes. A few months ago I consulted a first-class organ builder on the subject of having pipes attached IIo examlaed it. and informed me that the swell box had just been made to encase what pipes there is in, and no more ; and that if I wanted pipes attaching they would have to be placed outside the case,—a piece of business my iweUiak pride objects to. Will any trot her reader (or sister either; give me their kind suggestion?—Tirfc Hahuoniois Cotton Spinner.

r^Md.]—TABLKSWITHOUT DECIMALS.—I am of opinion that for certain practical and common purposes all tables which can admit of figures—without minute decimals—would be a boon to numbers of working mechanics and others not having the power of making calculations; and I know of no meiiuiu equal to the English Mechanic to start the system. 1V*ill any brother reader kindly arrange a table—free from decimals—giving the quantities of water, in pounds, ounces, and parts of ounces (of course avoirdupois), required to condense a cubic foot of steam, eo as to produce a practical working vacuum, the steam to Increase from common atmospheric pressure to lib. per square inch, up to 101b., or upwards, with size of condenser ?—B.W.

[Sg67.]-MAGNETIC NEEDLE.-Will any of your subscribers answer me this question :—Supposing- I have two magnetic needles centered, one strongly magnetised and theother only faintly so, from which ought I to get greatest deflection, placing each in succession in the same coll'- —Br/ra

[3968.]—KILN.—Will one of your correspondents oblige m-3 with a description of a good kiln for burning lime, and state the proportion of coal used to lime burnt, also the quantity burned per day? A sketch would be useful. Is there auy good practical book on the subject ?—L. M.

[3969.]—COPPER BOILER.—Can any of my brother readers kindly inform me of the most efficient design of capper boiler to drive an iron boat Gtf Inches long by &\ inches beam, the engines of which are two cylinders, each l£ inch bore and 1} inch stroke; and what would be the best form of apparatus and fuel for firing same. The boat is 0 inches deep ?—O. G.

C3970J-FOOD FOR COWS.—Will any reader tell me how to steam food for cows; to do titty bushels at once. Would it be cheaper to have an iron tank or brick and cement tank .' —K li.

[3971]-DISPLACEMENT OF SHIPS.—Will any of our correspondents be so kind as to'give me a proper way to find the displacement of a ship? I nave not given any dimensions, but those that can do it, can take a length, breadth, and depth for themselves. I know that it is a difficult problem, but surely there is one amongst our talented brothers that can assist me.—G. li. D.

USEFUL AND SCIENTIFIC NOTES.

IMCK.VEY SCIENTIFIC ASSO CIATION.-Mr. H. W. Emon. the Hon. Sec. of this Institution has sent us a report of its third annual meeting just held, from which we gather that the institution la flourishing. The number of members wai actually twice as great as at the commencement; the papers, Ac, read had been more interesting and numerous tknu on any previous occasion, and the library, which had only been commenced this year, already comprised many valuable works. The conversazione, held at tho commencement of the session, was attended ;by a much larger number than was expected. It was annouueed that during the summer months excursions would be organised to places of scientific Interest, also to tho various public museums.

A NEW PROJECTILE.—Captain Ericsson announces, in a communication to the American Jrmy and Mar) Journal, that be has perfected a system of submarine attack by which he can destroy the largest ironclads ever bnllt. The resistance of the water is so <_'reai that explosive projectiles have always proved failures hitherto when designed to strike below the water-line. Captain Ericsson Is confident that he has devised a projectile which will overcome the difficulty caused by this resistance. It is an elongated shell, charged with 3001b. of dynamite, and shot from a lain, gun, at such an elevation as to enter the water near the hostile vessel, and strike the hull anywhere below the water-Hue. It U fitted with a percussion cap, which explodes upon very slight impact against the bull, so that the velocity of the shell when it reaches its destination need not b.s high. The gun is carried on a awift armoured boat, protected by a turret. Captain Ericsson intends to make a formal oiler to test this invention. He is ready to fit out, at his own cost and risk, a fast screw vessel, with two I51n. guns of the kind described, if somebody else will furnish the ironcloJj to be experimented upon. In the politest terms he does this country the honour to single out the new

i «j' acl*(i Devastation as one of the most splendid iwotmtna of an asmoured war-vessel which can be produced, and challenges her to come out and encounter his torpedo.

BRADAWLS —It Is stated, remarks the Scientific Xenev, that there are but three bradawl makers in London, and a bradawl seems to offer such a small field for improvement that a patent would appear to be scarcely worth applying for; yet this Is not the case. An Improvement has been invented, which consists in making the bask in two pieces, one Secured to the handle, and hRVlng thereon a tapped or otherwise formed upper part, made to tit in aud correspond with the second piece, suoh second piece being a tapped or otherwise formed oap, furnished with an Internal projecting collar or shoulder, both pieces being constructed to receive

the blade of the bradawl In such a manner that, when the blade is inserted in the busk, the nozzle or screwed cap may bo passed over such blade, and may, when screwed up or home on the busk, abut against a corresponding projection-collar on the blade of tho bradawl funned for the purpose, and mode to fit in such a nozzle or cap.

WARMING CAERIAGES.-A new method of warming first-class carriages in express trains has been adopted In Bavaria. A special van is attached to the train, and contains a powerful "calorifcrc," and the heated air 1b conveyed to all the carriages of the train by means of india-rubber tubes. The experiment with first-class oarrinires is reported upon so favourably that the authorities have determined to apply it to all the carriages on the Bavarian lines, and it is expected that it will soon be adopted on all the German railways.

METHOD FOR RENDERING WOOD DIFFICULTLY COMBUSTIBLE, AND FOlt PRESERVING IT WHEN UNDKRGKOUND.-Dr. Reinscn recommends the following:—The wood, which must not be planed, is placed for 24 hours iu a liquid composed of 1 part of concentrated silicate of potasaa and 3 of

Fure water. Alter having been removed from tills iquid, and dried for several days, tho wood is again soaked iu this liquid, and, after having been again dried, painted over with a mixture of 1 part of cement and 4 parts of the liquid above alluded to. After tho first coat of this paint is dry, the painting is repealed twice. Of the palnt-mlxture alluded to, largo quantities should not be made up at once, because it rapidly becomes very dry and hard. Wood thus treated is rendered uninflammable, and does not decay underground.

SOME HINTS ABOUT SCREWS.—Where screws are driven into soft wood and subjected to comlderable strain, they are very likely to work loose: and It is often difficult to mako them hold. In such cases, says the Canadian linilder, we hare always found the use of glue profitable. Proparu the glue thick ; Immerse a stick about half tho size of the screw and put it into the hole; then immerse the screw, and drive it home as quickly as possible. When there is an article of furniture to be hastily repaired, and no glue is to be hod handily, insert tho stick, fill the rest of the cavity with pulverised resin, thou heat the screw sufficient to melt the resin as it is driven in. Chairs, tables, lounges, &c, are continually getting out of order in every house ; and the proper time to prepare them Is when first noticed. If nesleoted the matter grows still worse, and flnallv results in laying by the article of furniture as worthless. Where screws are driven into wood for temporary purposes they caa bo removed much easier by dipping them in oil before inserting. When buying screws notice what you are getting; for there are poor as well as good kinds. See that the heads are sound and well out s that there nre no flaws in the body or thread part, and that they have gimlet points. A screw of good make will drive into oak as easy as others into pine, aud will endure having twice the farce brought against it.

CHANGES IN FISHES.-In the American Naturalist, Charles C. Abbott, M.D., gives some acoount of the changes in the fishes of New Jersey within a few years. A slight local disturbance quite alters the fauua. Thus in 1867 a small, never-faiiing brook, emptying into the Assurapink, was populated by chubs, dace, and minnows. In July a heavy, Budden fall of raiu caused a rise of water' but did not alter the brook enough to attract the attention of those who lived near it. After the subsidence of the water not ono of these flsh could bo found there, while their place was takeu by roach, mullets, and red-fins, which are now abundant, while not a chub con be found. Dr. Abbott mentions several fishes that were not inhabitants of the New Jersey streams twenty-five years ago, which are now quite abundant.; aud ho is greatly at a less to Imagine how thoy can have reached these streams. Ho mentions the interesting oase of tho gizard shad, which Is sometimes carried by freshets Into inland streams or pouds. A pond near Trenton was stocked with them In 1837, and is sow full of spe-imens, weighing sometimes five pounds. They have become so different In colour from the same flsh as found In the Delaware and on the cost, that Dr. Abbott at first thought them quito distinct: and ho says they have changed considerably, but only In colour, during tho last ten years.

DKEP-SEA DREDGING.—The Admiralty have acceded to the request of tho Royal Society by again placing Her Majesty's surveying steam-vessel the Porcupine at their disposal for another deep-sea exploration, to commence iu the latter part of June. Mr. J. Gwyn Jeffreys wlil take charge of the first cruise, which is intended to be across the Bay of Biscay, along the coasts of Spain and Portugal, to Gibraltar. Dr. Carpenter will there succeed him in the beginning of August, and proceed into the Mediterranean, after endeavouring to trace the direction aud nature of the currents at the Straits. Professor Wy ville Thomson will probably join Mr. Jeffreys. A photometric apparatus has been contrived by Mr. SiemenB for the pur pose of ascertaining the depth to which Bolar light penetrates the sea ; and other questions of considerable interest will be investigated in this expedition. But we regret to find that the time is so limited for such an Important object.

THE GREASE TREE—In China there grows a tree known as the 3rease Tree. It is said that large forests of this vegetable lubricant are to be found there, and they form the source of a considerable local traffic, This tree not very long ago was imported into India, and it is said that the experiment of cultivating It there has proved quite successful. In tho Punjaub, and North-western provinces generally, it grows as rapidly and as vigorously as In its native soil, and there are already thousands of t eos on the government plantations yielding tons of seed, admirably adapted to a variety oi commercial purposes. Dr. Jameson, a chemist in the Punjaub, has prepared hundredweights of grease from this particular tree; aud has forwarded on trial a portion of it to the Punjaub Railway to have its qualities tested in a practical manner as lubricating material for those parts of

machinery constantly exposed to frictiou. The <rease thus obtained forms an excellent tallow, burning with a clear, brilliant, and what is infinitely more to the purpose, a white light, and at the Bame time emitting not a trace of any unpleasant odour, or of the ordinary disagreeable accompaniment of combustion—smoke.— Notes and Queries on China and Japan."

EXHIBITION OF FANS,-At the South Kensington Museum there has been opened to the public an exhibition of fans. The exhibition Is a part of the scheme of the Department of Scionoe and Art for tho T' TiuBtrn°tion of women. To promote this object, the Depannent offered prizes in competition fur fans painted by the students in the female schools of art In 1JGS, aud again Iu 1869. The fan-mount to which In the first of these years the chief prize was awarded, is Included in this exhibition, and it is intended to continue the competition. Her Majesty also purposes to ?, ir,,n fan prlze ,or competition at tho International Exhibition of isn. The Society of Arts has also offered its gold medal (of the value of 21 guineas) for the second-best fan exhibited. The Lady Cornelia Guest and Baroness Meyer de Rothschild have each offered a prize of £10 for the two next best fans. A sum of £50 will be awarded and spent iu various amounts by the Science aud Art Department, for Inns produced by female students of the schools of art in the United Kingdom. Among the more curious of the fans exhibited is one dated 1660, the mount of which is a landscape and figures embroidered in silk. Some of the carving of the mounts is exceedingly dellcato A fan, one of the weddiDg presents of the Empress of the French, is especially noticeable for its display of lino open cutting in so brittle a material as motuer-o'poarl. Some of the fans possess historic interest, two or three being associated with the unfortunate Marie Antoinette. The Queen contributes sixteen examples; the Empress of tho French, thirty-live; ond the 1 riucess of Wales, Princess Christian, and Madame la Comtesae de Paris, are among the contributors.

SCRAPING SLIDE VALVES.-Mr. W. P Cowan of Brooklyn, New York, writes to the "Scientific American" to the effect that few workmen know how to scrape properly. He says:-I have always found the scraper works best after a smooth file; everything should be finished with the smooth file previous to tho scraper being used. I have seen many workmen leave too much to be done by tho scraper. Now that is a gross mistake; every artlole ought to bo fitted as well as possible before being touched by a scraper; otherwise a bad job Is almost certain to be the result. The scraper should always be used obliquely to the file marks, never across, at any rate. Nothing makes a better scraper for wrought aud cast iron than a taper saw file, and for brass a flat scraper must be used if food work is wanted; say about lin. broad and S-32ln. thick. A saw flle scraper is too keen for brass. In all railway shops In the north of England scraping is much used, and with tho best results. We always scraped slide valves, motion bars and blocks, and axle boxes. It is certainly a very unworkmanlike way of J""1;log out a slide valve and leaving It to work itself ■ 5 « ls tant<"nount to saying it can't be made tight. Most of the first-class marine engine builders in Great Britain scrape valves, &c. In one case List year it was tried to do away with the scrapor on a pair of large valves,; but on the trial trip the valves got cut up awfully, Bo scraping is considered a necessity.

GRAFTING IN CHINA.—A very peculiar method or grafting is practised in China. In spring the young shoots of the chrysanthemum are Inserted into the stalk of the a>'» plant (wormwood ?), by makin g an InTMTM. "oss shaped, in tho stem of the latter, snd binding the two tightly together with a piece of oast or hemp. After the incision has been properly bandaged; a flower-pot ls put over it, bottom downwards, the plant passing through the hole In the pot, which does not rest on the ground, but upon four bricks placed under it, about six inches high. Earth is then put into the pot, and the plants gradually unite, taking root at the tame time in the pot. As soon as the chrysanthemum flowers, the stem of tho ei is severed immediately under the pot, and tho whole is removed from the nursery to the garden or verandah. The grafting "strengthens" the chrysanthemum, which would otherwise produce but a very poor flower. The method ls most ingenious, ana the plants seem to unite very readily.—Notes and Queries on China aud Japan.

REFLECTED LIGHT.—A series of experiments with a novel form of apparatus tor determining the amount of light reflected from metallic surfaces at different angles has shown Professor Rood that a mirror silvered by Liebig's process, uBing the silver Bide at an angle of 45 deg., reflects 91 per cent, of the light emitted by a flame, and from tho glass side 7H per cent., while an amalgam mirror at the same augle reflects only 45 5 per cent. The apparatus aud method employed will be found described in the "Journal of Gas Lighting, Ac." It would be interesting to kuow the reflecting power of the beautiful platinised mirrors uow coming into use.

MILK—It may be worth mentioning, for the soke of people employed in white load works, and ether occupations which expose them to the same risk, that milk taken as a drink has been found as useful as the dilute sulphuric acid in preventing colic.

GLUE.—The value of glue, that is, the amount of pure gelatine it may oontain, may be determiB il by precipitating this body with pcrmtrate of mercu y, a standard solution of which tested with a kuown weight of pure gelatine may bo employed.

THE ENGLISH MECHANIC LIFEBOAT FUND.

Subscriptions to lie forwarded Ui the Editor, at the office.

31, Tavistock-street, Coicnt Garden, WO.

Amount previously acknowleuij'd .. ..£180 10 10

Vibrator 010

Zeta 0 10

J. Lillcr 010

C. Forrest, juu 096

Frank Fairlcigli 0 2 «i

£180 18 10

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ANSWERS TO CORRESPONDENTS.

',' All commtinic&tfoag should be addressed to the Editor of the English Mechanic, 31, Tavlstockstrcet, Covent Garden. W.C.

ADVERTISERS' TESTIMONIALS. Messrs. Ashwohth, of Ashley-lane, Manchester, after advertising their patent "looped" portfolios in the English Mechanic a few times, say:—"Several hundred of these binders for tha English Mechanic have already been sent out."

CAUTION. Messrs. Mottkrshead, Market-place, Manchester, say;— "Having noticed in a recent number of the English Mechanic a caution about certain members of the Ions; firm calling themselves "Claud & Co., Cheltenham," wc send a line to say that we have been favoured with an order from those individuals, but, thanks to your notice, were on our guard. Wc sent them, as we usually do to strangers, an invoice, requesting a remittance before we sent the goods. Of course we have received no reply (since the 2nd April). Wc have since had an order from Parks St Co., Manchester Warehousemen, Alvington, Glo'ster, which we treated as above, with exactly the same result. We should judge from the writing that they are the same people. Perhaps another caution about them might be useful."

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A. W. Marshall would oblige by sending the information for "Xanthos" and "Cottou Clerk" to our pages for the benefit of others as well.

Rev. E. Krrnan. with MS. complete to folio 173.

E. Slatsx, on Cotton Spinning, next week.

rETKaFiKLDiNO,—We cannot forward trade circulars.

"Hints to Astronomical Students " next week

A. Tolhausen. with MS. on Materials, ike

"Health-helps for Self-helpers " next week.

Thos. J. O'connor,—See " Extracts from Correspondence," page 212. We hope none of our correspondents skip this interesting column.

Polson.—Advertisements must he paid for.

Frrd, Baldwin.—We know nothing about the pedespced beyond what appearad on page 61. We do not answer by letter.

Figure or Thi Earth.—Mr. Jas. Beardsley has written us a long letter, which may be summarised in a few sentences. He disclaims any connection with "Parallax," Mr. Hampden, or Mr. Carpenter, as he knows nothing of them, and and has not read anything they have written. Mr. Beardsley thinks that as he is honest and independent in the utterance of his opinions, he is entitled to a fair answer, and not misrepresentation or abuse He considered it a pleasure to hold communion with such a correspondent as Mr. Tyderaan, "who calls in question my sentiments in a charitable and concise manner, without rancour and without abuse."

T. J. O'connor—The Philosophical Magazine is published by Taylor & Francis, of Red Lion-court, Fleet-street, E.C. Price 2s. monthly.

J. S. W.—We cannot give the addresses. You might put yourself in communication with such manufacturers by an announcement in the Sixpenny Sale Column.

Kate Douglas.—Too much like an advertisement.

E. HATCHifi.—We kuow nothing of the party you mention. We should prefer consulting a regular medical man.

Reeds.—The English Mechanic is not a medium for advertising quacks.

A Countryman.— We cannot supply them; but they are sometimes offered for fate in our advertising pages.

Albert Megton.—Persuade your sister to thiuk of something less foolish. We never attempt to help or advise in such cases.

The Sixpenny Sale Column is the only place in which can appear queries sent by .Staem, S. D. T., E. G., W. R., A. 0. S., Beta.

G. C—It results from several causes—bad teeth, disordered stomach, consumption, Ac, and cau ouly be cured by consulting a medical man

A Pressman.—See Reply 3907, in this number.

Canto. - Your advertisement is repeated, but the fault is due in great measure to your own indistinct handwriting.

Henrt Cotton.—Both ends of an ellipse are equal. ovnl w egg-shaped; hence its name, from ova, an egg.

Anti-egyptian.—We cannot. A query appears in this number on the subject, and will probably bring answers to suit you. .

Jeunk Homme.—Information on the subject appeared in last volume.

Samuel Cobirn.—All advertisements in the Exchange or Sixpenny Sale Column are payable in advance.

Pawnbroker.—See back numbers. You don't entrap ns into another discussion on the "wheel question," if wc know it.

Topst TumvT.—An exceedingly silly question.

A. G. Prrrino.—See reply to Canto.

H. S. Savory.—Thanks for patterns.

Wm. Cartknter.—Wc really cannot afford space.

J. R. 1.—lu duu time.

J. T. B. (Chelmsford).—Thanks. As we have refused Mr Beardsley any more space, we think the controversy on the rotundity of the earth should cease.

J. H. D.—Arrangements are being mtde to publish the English Mechanic early on Thursday morning, and consequently not so much in advance of the day of publication as at present.

J. B. W.—We cannot act as arbitrators.

J. Barry.—The fault is with the Poet Office.

W. T. J.—We can only express our sorrow that the English Mechanic Lifeboat Fund accumulates so slowly.

Semper Paratcs.—We hope to be able to produce nn index of Notes and Queries without extra charge. We cuunot recommend anyone's goods.

Artisan will sec it is an American invention.

W. A.—Send us a thoughtful and condensed letter on "Galvanism as a Medical Agent," not theoretically considered, and we will insert it.

J. B. asks what he can do in return for the assistance he has received from the English Mechanic. Introduce the publication to others who may be in want of similar assistance.

It. W.—Anyone may ask for or communicate information through our columns. We are no respecter of persons. No charge is made.

Cotton Spinning.—Several letters on this subject are postponed.

"Science Fob The Young" next week.

THE INVENTOR.

IN obedience to the suggestions of a number of readers, we hafedecided on appropriating a portion of our sp-ice to a condeosedlist of patents as nearly as possible up to the date of our Issue.

An

APPLICATION'S FOR LETTHtH P\TBNT DUltltfQTBB WBttK BNIKNG MAY 33, 1870.

ItfS J. L. Monteflore, 53, Kensington Gardens-square. Improvements in the manufacture of bronze.—A communication

1100 K. P. Jones, Mlddlcaborough-on*Tees, Improvements in the manufacture of Iron

1410 0. Hunt. Nine Bims, engineer, improvements in retort* and retort settings

1111 J. H. Player, Birmingham, apparatus for the manufacture of phosphorus

1413 H. B. Qreenwood, Welwyn, Hertfordshire, apparatus for holding window sashes or shutter*.—A communication

1415 M. Benson, 9, southampton-butldlnzs. improvement* in steam pumping or blowing engines.—\ communication

1414 J. Agnew Liverpool, a new and improve! nwdicinal preparation or cod-liver oil

1415 B. Hunt, 1, Serle-street. Lineoln's-lnn. improvements In thi manufacture of certain pigments or paints.—A coin mumoat Ion t t

1116 R. Green, Phoenix Works. Wakolield. improvements in the construction and arrangement of iteam boilers

1417 B. Blrnbnum. New Broad-street. London, an Improved fn atoning for leggings, waiters, stars, and corsets

1418 P. J. Ciea-er. (ted Lion-street, improvements in apparatus for moulding nod stamping soap

1410 B. Lawrence,*Baslnghall-streot. an improved ink. or improved inks for printing and other purposes.—A cjinimmicition

1490 T. G. Webb, Manchester, improvements in the manufacture and ornamentation of articles of glass

lt.M G. Nelson, Liverpool, improvements In apparatus for raising, lowering, and detaching ships' boats

1422 H. van La* them. Berlin, dial universal

1423 T. P. Young, Bury, Lancaster, and J. Thomasson. Hadcliife. improvements lu looms for weaving

ll2t G. Hodgkinson, Manchester, improvements In the tntnafaoture of toilet quilts, toilet «r table covers, qulltinga, aud the like articles _

7 1426 J. Caathelas, 10, K-ne Saint Croix, Paris, improvements in the manufacture or artificial alkaloids

112o J. G. Oharllck, 1, Park-street. Dor set -square, improvements in holding frames or brackets

1427 W. Waller. 31. Grey-street, Newoastlo-on-Tyne. Improvements in f urn aces

1138 D. McUolley Weston, Boston, Massachusetts. U.S.A.. im

Erovements in the machines for and the manufacture of nit ted goods

1420 W. B. Newton. 83. Chancery-lane, an Improved automatic barrel-Ailing apparatus.—A communication

1430 J. Starley, Coventry, an improvement In sewing machines

1431 W. K. Lake. Southampton-buildings, London, improve* ments In looms for weaving.—A communication

1432 W. Brodio, Edinburgh, improvements in the construction of vehicles used on railways

1433 G. B. Turner, The Woods, Charmouth, Improvements in winnowing or dressing machines

Mil P. Edwards, Nottingham, improvements in the manufac* tnro or production of lace

1435 B. JPevton, Birmingham, improvements in the manufacture of welded Iron or steol tubes

143d R. Peyton. Birmingham, improvements in the manufacture of metallic bedsteads

1437 G. T. Boutllold. Lnughberoiiith-park. Brixton, improvemetitain looms ior weaving.—A communication

1438 A. M. Clark, 53. Onainor.v-lft.ia. impiMveiniiU in inachines for manufacturing cigars.—A communic ition

1439 J. Stoart.fll, Saint J wies-road, Beruioudiuy. improvements In aleansinir ships' bottoms

1440) J. Diggle. KadclifTe, Lancaster,: and H. Booth, Pllkiugton improvements In looms

1141 B. C. Muzzall, Windsor, improvement* in the construction of aobool furniture

1442 8. Baerleln, Manchester, improvements in doubling cotton

1113 J. Smithies and J. Smithies, improvements in the manufacture »i wov<»n fabrics

Hit W. B. Gedge. 11. Wellington-street. Strand, improvements in steam engines.—A oommuoloaMon

1111 G.Zanni, Sidmouth-streec, /.iray's-lnn-road, improvements In magnfto-eleotrlc telegraphic apparatus

1440 J. A. Hopklnson, and .1. Hopkinsun, juu.. Huddorsfleld improved means or apparatus Tor admitting and regulating the supply of air to steam b»ter and other farnaeas

1417 B, Oxlond, Oompton Gilford. Plymouth, improvements in the manufacture or sulphuric acid

1148 G. W. Kendel. Elswick Works. Newcastle-on-Tyne, improvements In cartridges for ordnance

1410 B. Pitt, Newark Foundry, Bath, Improvements In valves for drawlnse off water and other tlnids

1450 J. sctitoss, 46, Cannon-street, London, improvements In fastenings applicable to purses and such like articles.—A communic'tio'i

liii W. >i f.«Vi. Snthtronton-buildlng*, t-onlm tm-i'voments m m I-.i.ii ■< f >r i'i'lying oottou and otno.-lidrou, .ualerlals— A (■tuiniunicvtion

li.vj J. llHiiii. ■>. i-i^u-v, i.iiprovemi'itu in treatinz oils

1453 W. L. slitchell, Kirkoaidy, Pire, improvements iu loams

1154 J. P. Blike. Massachusetts. U.S.A., improvemeati in rolling metallic rods or wire

1155 J. Breoden, Birmluguam, Improvements in lift and ii>roo pumps

lloo A. M- Clark. 53. Chancery-lane, improvements in apparatus for the production of g.%ses for lighting and heating purposes.—A communication

1467 M. Girnud, Hue Sauzay, No. 22. Constantino. Algerio, improvement* in machinery for tilMn< or digging land

1158 J. H. Johns to, 17. Cia? >li'^-inu-tield8, apparatus for firpttorviog butter aud otner similar substances.—Acommunicition

1150 G. G. \i. Hardtngham, 2H. Great Goorg«-st re«t. W"cstml'i*ter. Improvements in tohaoco pipes aud cigar h>>l'ior«

1490 A. Taylor. Lydbury, Salop, improvements iu rocHot project' Les for purposes of war

l«l T. Hodson, Mnuchester, impfovemints in the manufacture of piled fabrics

1WJ T..I. Smith. 1«. Fleet-street, an improve! arrangement of apparatus r<>r dimtni*htng the friction of spindles. Kxles. nod other similar rotating botfle*.— A communication

lies J, J. Denouat. New Cross, Improvements in eavalopLns medicinal and other liquids

1*»1 D. 0. Low.ner, Ohurch-strcst. Warrington, iraprov-©ments in wire tiesfor securing baioi of hay, c-jtton.au-I oc tier merchandise

1465 W. Harwell and G. B. ''mlth. Birmingham. lmnrov«inent» in securing the nuts of the screw baits used in ttih jointing; trie rails i>r railways

14M H. Oaterkamp. Eschwellorpurape, near Aix la ChapalU\ Prussia, lmprovt'1 nurk-'lrllltn r m ichini

1«7 A. M. Silber, Wool-strtet, Cheapside, and P. White. Cimherwell. improvements in apparatus lor lighting and heating purposes

1WS, G. Fischer, Brandenbounr. Prussia, it new steam boiler lirtng with c implete smoke ombustioti. *a

lbW tt. Harte.lJ. Arnvle-ro»d, KenslnjfLorj, ioi^r ivemsats In means andapp\ratus for effecting atrial loc jtnotlon w

1470 J. A. Ryke Van Den Benrh, Southsea. an impros-M ae» messenger or receptacle to be used for receiving pitpen*. parcels, and suchlike

1471 G. Simpson, Glasgow, improvements in machinery and arrangements for cutting or getting minerals

1173 T. H. Lloyd. Stookport, imi»rovuraprits in the construction and arrangement of valves

1173 W. Avery, ttedditch, improvements In cases or recaptacles for needles, pins, matches, pen*. o:irds, stamps, photographs, cotton, and other similar articles

U"4 P. Webley and T. W. Weblay, Birmingham, improvements In breech-loading fire-arms

1475 E. B. Allen, 31, Pel ham-place. Brompton, Improvement* in the construction ortramways and in engines and carriages emoloyei chnreon

117S P. J. Tolller. Paris, improvements in machinery for the manufftcture of strings aud cords

11771H. Kind, and O. Wells, Nottingham, improvements In steam and other valves

1478 B. Perowoe. Great Snoring, Norfolk, improvements in machinery for cutting turnips and other roots

1479 F. Mllnes. Camden Town, improvements in apparatus for healthily exercising the human frame

1480 J. Mncqueen, Mauchester. certain improvemanta in cardinn engines

1H1 W. B. H-tth.js, Oamlen-rnvl, Improvements in co>iior or refrigertting baer, liquors, or beverages

lis* H. A. Bonneville. 18, Chaussee d'Antin. Paris, a iw» and improved mode of manufacturing wooion flosri aid wainscots.—A communication

1133 H. A. Bonneville. 18, Chansee d'Antin, Paris, improvements in sewing machines —A communication

IM p. C. Bvans. Brimscombe Mills. Oloucester. and H. J. H . King. Glasgow, improve-nent* in apparatus for feediug wool, cotton, or other fibrous materials

11485 M. Bunion. South tmpton-bulldlngs, Improvem *nt* In the mode of supplying tamps or lanterns with atmoiphtrlo air. —A communication

1188 A. Lonr. **. Avleshory-street. Walworth, improvement* In means for rezulatiug the fl>w or cjutroliin ,- tti-j supply ot water or other fluids

1487 W. B, Newton, 86, Chancery-lane. Improved m^chfnery for grinding hand saws.— \ commu'iicAtloa

11S8 A. Browne, 85, Gracechuroh-stroei, improvement! in screw propellers.—A communication

1180 J. Head, Hlddlesborough, improvsments Iu setting horizontal stationary boilers

1490 W. K. Lake. Southampton-bnlldinrs, Lonion, improvements in machinery for sooaring, glossing, and otherwise treating leather.—A communication

1491 W. H. Lake, Soulhampton-bulldlncs. London, lmtirnvements in machinery for sewing boots and shoe*— A communication

111193 T. A. deCarvalho, 1, Park-villas, High-road, Lee, improvement* in ships and ves*e!s

«11403 M. Henry, OS, Fleet-street, an improved case holder or receptacle for matches.—A oommunioat ion

PATENTS SEALED.

3343 J. Bottomlev, and S. Bmsley, improrementi iu splnnfng flbrous substances

3376 H. A. Bonneville, a new and Improved stean boiler supply ooolc—A communication

3377 K. A. Bonneville,electro-mstallurgy. —A eommuuiiation

3378 H. A. Bonneville, improvements In elecfrio batteries.— A communication

3380 J. B. Crooo-Sptnelli, fmarovernents In means and apparatus for propolliii?and st'ierintt vessels

3381 BC&ound, an improved indicator for marking games of skill or ohanee

33si A. Nairn, improvements in steam carriages for common roads

3,'HH A. McNeill, a sare for ships and othir navigable vessels carrviu* mails, specie, and other valugbies

3-191 J. Fog/, Improvements In macQinery for dressing ua^a and stone and other hard materials

3193 S, Cotton, improvements in machinery for preparing

839S S. Ohatwood and T. Sturgeon, improvements in apparatus for forcing and drawing tiuids and liquids

34'J1 W O H*nn, iniprovesaents in the manuf.tctnre orhats

311* W. Pollitt, and W. J. (tnowles, impruvements in machinery fir washing, wringing, minglm;, cliuralnff, and mlxlnc fluids

3M3 3. Horrv. J. J. Perry, and L. tt. Perry, improvemsnts ia boxes for holding various articles

SWO J. Wood, J.Wood, and W. H. Wood, improvements In ventilating hats or other coverings for the head

3713 W. K<mnett, and J. Ourrall Improvemquts in kttohoo ranges an I lire-places or stoves

3599 G. P. Logan, a new or Improved means for utilising

WltS'O tltt it . - m

3779 G. n tmllton. Improvements In the construction or steam boilers

151 r. Whitehead, Improvements in wool combing and driwIok machinery

191 J. M i*le«sner. Improvements In apparatus for and in the treatment of liquid fuel

306 0. lUnaler and A. Keppler, improvements in propellers

63t) J. O. Worrell, improvements in apparatus applicable to the treatment of refuse for sanitary purposes ii7«J, J.Stevens. J. J. P. Stevens, and \V. A. Stevens, an improved apparatus for working points and signals on railway*

913 O. Cotton, Improvements Lu machinery for the maouuicturo or knitted fabrics

SKA A. Goddard and w. Flnley, michlnory for pill m*is mixlmc 'fid pill making

SUin. M. Feiton, Improvements in collars and cnfTi

3117 D. Barker, improvements iu the manufacture of varnish and varnish paints . ,

3113 J. Denis, improvements In the means of and machinery for producing pulp from wood

1133 &. H. Burke, Improvements In metallic barrels

3134 W. Parkins, improvements in fusees, matobe*, or other analogous articles

3125 J. Combe, improvements in maohlnory for hackling flax and other flbrous substances

3117 J. Brunton. improvements in working and loeking railway points andslguais

3434 J. Pitt, J Pitt, K Pitt, and W. Pitt, improvement* in machinery or apparatus for drilltiu, turnmi, or casting aud shaping metals or other materials

MM L Poohet, an improveJ apparatus for cutting or dresslug stone . t

SW9 W. Cross, an improved manufacture of shawls

3141 S. Fox and J. Kerntt, improvements In machinery or apparatus for boring, turuinic, and polishing ueusiU and bobbins

3455 J. Edwards and J. Quln, Improved means for preventmg roller laps on roller ends of machines for carding ojitw, woollen, flax, or any other flbrous material

3409 &. Milburn and T. Browning, improvements in drying machines suitable for drying ears of corn, gralu, seeds, aud other materials

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NOTICE.

FOR years past the English MECHANic,though professing to be published on each Friday morning, has in reality been published on the preceding Monday. We have, therefore, been obliged to go to press on Friday evenings, ora week before the nominal day of publication. As this arrangement has occasioned no end of inconvenience to correspondents and advertisers, it has been determined in future to go to press on Tuesday evenings, and publish early ou Friday mornings; in other words, on and after the. 8th of July next, the English Mechanic And Mirror Of Science will be published at the same time as the widelycirculated London weekly papers. In order that no inconvenience or disappointment may arise, our readers will oblige us by informing their respective booksellers or newsagents of the contemplated alteration in the day of publication.

We beg also to inform our Subscribers that we have purchased the copyright of Scientific Opinion, and that on the day mentioned—the 8th proximo, that well known and high-class scientific publication will be incorporated with the English Mechanic. Scientific Opinion has a good staff of contributors and correspondents ;these, added to our own, will no doubt materially enhance the value of the English Mechanic.

HINTS TO ASTRONOMICAL STUDENTS.

By T. W. Webb.

(Continued from page 74.)

IN a previous paper we discussed at sr.me length the nature of the images formed from luminous points by refraction on reflection, and the representation of stars by spurious discs, with their attendant rings. We will now proceed to extend oar remarks to the consideration of the telescopic definition of lines and surfaces. The character of this, after what has been said, it will not be difficult to understand. As the real discs of the stars, from their extreme remoteness, approximate, so far as our sight is concerned, to mathematical points, so, for the same reason, the natural outlines and boundaries of heavenly bodies become sensibly mathematical lines. But the mathematical line may be considered us composed of an infinite number of mathematical points; and its telescopic representation will therefore be equivalent to an infinite number of 8pnrious discs, each with its attendant series of rings. The resulting image, instead of being indefinitely and almost imperceptibly narrow, must have a sonsible breadth equal to that of the spurious disc ; and ihe edges of the infinitely overlapping rings wi produce as many narrowluminous borders on both sides of it as there are visible rings, each parallel to the bright band which forms the image of the line. Such is the natural result of what we have already attempted to explain; we have, however, no opportunity o[ exemplifying it in practice, there being no instance of a luminous object in the sky, at one , long enough, narrow enough, and bright enough, t) form such a telescopic image. We have, how ever, in the limbs of the celestial bodies, t'ie

external boundaries of luminous surfaces whicb answer the description as fur as one side of them is concerned. The surface itself mathematically represented by an infinite number of points, will produce a luminous image composed of an infinite number of overlapping spurious discs; and the outer boundary which terminates that surface will consist of the half of such an image of a line as has been described ; the other half being of course merged in the general illumination of the disc. Every line being referable to on infiuite number of points, and every surface to an infinite number of lines, and the image of a luminous point being strictly ascertainable as to character by the laws of optics, and determined as to magnitude by the experience of the best opticians, we have at length a clue which will guide us through all the details of telescopic definition. There are, however, collateral considerations which must be carefully borne in mind. The phenomenon is not only objective bui subjective —that is, it depends not merely on the existence of certain undulations, but in the capacity of the retina to appreciate them. Below a certain intensity, varving considerably in different individuals, the vibrations constituting light fail to produce any perceptible effect upon the organs of vision; and the office of the telescope in many cases is, by collecting a greater number of these vibrations, to produce the requisite intensity, and to strengthen the latent image till it excites the reiina to a sufficient degree. Thus, though the optical imago of every star is theroretically surrounded with a considerable number of rings, in practice our eyes can only distinguish a few of them, even around the brightest stars, from the rapid degradation of their light ; and as the stars diminish in magnitude, so the outer rings go successively out of sight. By the use of a larger aperture we counteract this degradation, and restore some of the lost rings; but as we call up, so to speak, the rings of the inferior magnitudes, so we bring into sight the central discs of innumerable fainter stars, which were before imperceptible, and whose rings arc still too feeble for our sight. And the same of course holds good with the external portions of the spurious discs which are in a similar way lost sight of, or brought into view, according to the visible telescopic brightuess of the star. In every case, therefore, of a luminous telescopic image, the theoretical result is modified by the receptive power of i he eye, and the aperture of the instrument enters materially into the result, not merely as giving a larger or smaller spurious disc, but as making visible a greater or less number of rings, or, in the case of a line, the luminous border which they produce by their superposition.

We are now in a position to understand why the outlines of every telescopic image, the limbs, for instance, of the moon and planets, though remaining perfectly distinct, in a good instrument, up to a certain degree of magnifying, become progressively less hard and cleanly-defined with every subsequent increase of power. In their own nature they are throughout only approximately sharp, being composed of an infinite number of overlapping external halves of spurious discs, whose light decreases rapidly towards their edges. As long, however, as the power employed is insufficient to give a sensible magnitude to the radius of the disc, or at any rate to the portion of it where the light sensibly fades, so long the sharpness of outline continues apparently perfect, whatever eyepiece may be employed; but under the same conditions of magnifying which render the spurious disc large enough to affect the eye with the idea of size, we shall find tin hard definition of outlines begin to fail. Theoretically considered, the latter as composed only of semi-discs, should bear twice the amount of power with equal distinctness but these are niceties into which we need not enter. We may however remark, what is fully borne out in practice, that the sharpness of planetary definition always is in proportion te the size of the telescope, the diameters of the spurious discs in which it depends varyin inversely with the aperture. At first sight it might appear strange that we do not see the limbs ot the moon and planets attended by a b jrder r suiting from the presence of, a-, least, the first interference-ring, and that the detaiU of their surf u e? are not rendered indistinct from the same cmsc, but a little consideration will show that such an effect is imperceptible for the >ame reasou that rings are not noticed round the s nailer stars—namely, the want of intensity of light, the reflected lunar and plai etary beams

being incalculably more feeble than the intrinsic spleudourof stars of any considerable magnitude. I have, however, noticed a border round the limb of Venus, undoubtedly due to such a cause, and in all probability it would he very conspicuous round the sun, were it possible to view him without such a darkening apparatus as must extinguish all such appendages. The knowledge of these facts serves to explain why the details of planetary surfaces are frequently not so welt made out with the largest apertures as we might have beforehand expected. The anionnt of light may he sufficient to render the interference-rings visible, which, overlapping each other throughout the luminous area, must produce a certain amount of hazy indistinctness, or what is commonly termed a "glare." Hence there is often a gain in the definition of minute details bv the reduction of light through moonlight, twilight, or haze, and this may probably be the reason why every telescope usually shows such details best with a certain amount of power—namely, that which without expanding the light to too great feebleness, reduces it so far as to render these rings, and the resulting irradiation or glare, insensible.

We have thus pursued the subject of definition to a considerable extent. The different modes, however, in which telescopic vision may be effected will render a little further investigatioa necessary at a future opportunity.

ELECTRICITY—ITS THEORY, SOURCES, AND APPLICATION. By J. T. Sfrague.* (Continued from page 218.) -i Q A The next great class of electric gerte-L*-J\_/« rators includes nearly all the other forms of battery. The principle is the employment at the negative plate of some substance containing oxygen in sneb a condition as to be readily parted with; thus the hydrogen instead of being set free, decomposes this substance, forming watei; he ingenuity of inventors has been largely exercised in varying—1st, the negative plate; 2nd, the oxidising agent, this latter being either liquid or solid. By keeping this classification in view, the principles and qualities of the different forms are rendered much more comprehensible than by a mere description of successive inventions.

131. Groves's Cell.—This was the first devised of this class, and in most respects is the best, platinum being the negative metal, and nitric acid the oxidising agent. The form is not essential, but it is usually made with flat plates; the platinum in a flat and narrow porous vessel to reduce the quantity of acid to the lerust, the zinc being either in two plates connected together, or one plate bent so as to surround the porous vessel at a distanceof about three eighths of an inch. Fig. 40

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cylindrical porous jar, as in Fig. 41, which will serve as the type ot this form.

133. Cauboxs.—The employment of carbon is attended with some difficulties which call for attention here. Carbon is one of the most remarkable of the elements, possessing what is called "allotropic" forms, in which, though chemically the same thing, its physical properties are different, with different relations to heat, electricity, and light ; such varieties are the diamond, charcoal, and graphite. It is this latter which is useful in electricity, either in its natural form of plumbago or black lead, or the artificial deposit of gas carbon. It must be clearly understood that this substance is not coke; coke is the solid residue left after distilling coal; the graphite comes from the gat, the rich hydrocarbons of which are decomposed by contact with the heated retort, on which they form a shell •, it is, in faot, a.'great nuisance to the gas maker, as it arises from the destruction of the richest gas, injures the retorts, and wastes the heat; in the gasworks it is called "scurfmg." The densest and hardest is the best for electrical use, and some which comes from abroad is far superior to anything our English c >als produce ; it should be almost non-absorbent, and ring like B metal when struck, and have a clear gray colour, not black. It is rather costly when good, simply because of the great diffioalty of working it. Other substances will answer, such as the mater ial of black lead crucibles, which is indeed made up for the purpose,

The chief difficulty with carbon is making the connection with it; this is commonly done by simply fixing a clamp on it, in which case a piece of platinum ought to be interposed between ttie two surfaces. A better plan is to deposit copper on the upper part, and then solder the connection to it, as this gives continuous circuit; the copper takes on it just as it would on a metal. There is one drawback to this, the same in fact which requires the platinum interposed in the first plan ; the acid both creeps up the surface and soaks into the substance, and then acts on the copper and destroys the connection. I have devised a perfect remedy for this which I do not think has ever yet been published. Before use I thoroughly dry the carbon and mark on it the point to which the liquid will reach, and then moisten with water this part, and also the extreme top where the copper is to go; the intermediate part is then heated by a Bnnsen's gas burner, and touched carefully with a piece of paraffin as long as it will absorb any, taking care none runs over the surfaces to bo used; with care this intermediate portion may be thus thoroughly saturated with paraffin, which resists contact of liquids, and on which acids have no action; the copper is now deposited, and the connection fixed, and then the copper surface and top of the carbon is covered with a thick coat of paraffin, which serves as a complete protection.

134. Other materials have been employed, as lead or iron, pi itinised. Cast iron has been strongly advocated under the name of Callan's, or the |Maynooth cell; a very few words will sum up their qualities. They are worthless. If any one wishes to lose his temper and his money he can use a cast iron battery, with some certainty of success. They waste the acid frightfully, they boil over suddenly, in fact they do everything we should wish not done, without having one redeeming quality to atone for their evils.

135. The relative merits of platinum and carbon depend on circumstances; the first is most expensive at first (especially as it is bad economy to use very thin sheet, which is a bad conductor, and soon becomes brittle and breaks up), but it gives a slightly higher force, and is preferable if the battery is to be much used. Still, for ordinary use the carbon answers every purpose, and is much more commonly employed. The actual conditions aud expenses of working are the same with both, and the following remarks apply to both, though the experiments were actually made with a carbon plate.

It is impossible to give an exact statement of the reactions which take place in the nitric acid cell, as they are continually varying with the strength of the acid. HNOj may lose 1 atom of oxygen, becoming IlKOs nitrous acid, under one equivalent of action, which provides II, to from Hi 0 water; but one atom of hydrogen is •equally able to take up one of oxygen together with the hydrogen of the acid; thus UNO., + H -becomes Hs O + NO, ; or the same reaction <t:iking place with the residue (nitrous acid) of the first case HN03 + H.bfc .mes H2 O ■+• NO. lu each of these cases the work done electrically,

by one atom of acid would be different. The principal action which really occurs is the first and third combined, HNO.1 + If3 becoming 2 H, O -)- NO, and according to this, one atom of nitric acid is effective for one had a half equivalents of electrical action; or to express it practically, though not in the true chemical language, two-thirds of an atom is the equivalent. This action is however complicated with others, for the acid is even totally deoxidised and converted into ammonia to some slight extent. Owing to this and to the loss by evaporation or carrying away of acid by the escaping gases, and by leakage through the porous cell, the working equivalent or value of the acid can only be settled by actual experiment, and in addition to this, when we buy nitric acid we only get a solution of it varying very much in actual strength. I therefore have calculated a table showing the properties of the acid at the various strengths; it is not prepared for analytical, bat for practical use, and is based on life's tables. Column I. is the specific gravity as given by him; Column II. is the percentage of true acid HNOs Le e's tables are based on the anhydride Nj Os formerly regarded as the acid, but I have calculated the true acid from his figures. Column III. is the number of atoms of 63 grains weieht contained in one lb weight; 'and Column IV. the number of those atoms in 1000 grains fluid measure; these two I have calculated from'thc percentage, and they will furnish every required information as to the work which acid of any strength is equal to.

[table]

28, is 2HXOs + 3H,0. This is the strength to which boiling brings both stronger and weaker acids and distils unchanged at 248° Fah., but is not, as sometimes stated, a definite hydrate, as it varies according to the pressure.

30 and thenjabouts, is double aauaforiu, and about 63 is tingle aquafortis.

136. The following experiments will both illustrate the uses of the table and the actions of the battery. The acid used was pure, intended for analytical purposes, its specific gravity 1-3175 giving, by averages between No. 49 and 50 in the table, a value of 10-58 atoms per 1000 grains, or 5-29 for 500, the quantity used in the porous cell, which on the above theoretical considerations should furnish at two-thirds 7-03 equivalents; 3000 grains measure of sulphuric acid solution were used in the outer cell equivalent to the consumption of 12 units of zinc, and a sheet of copper was arranged to receive a deposit of copper. The cell continued in action for nearly 7 hours, giving a deflection ranging between 67s to 55° and at last falling rapidly to 20°. There were deposited 8-64 nuits of copper, while 10-21 units of zinc were dissolved, showing B loss, by local action, of 157 units. I afterwards allowed the action to go on as long as any took place, but only 123 more of copper was deposited, and 3 of zinc dissolved, showing how much the local action increases towards the end; it was more than 14 per cent, beyond the 5 allowed in calculations for the simple cell: as to the nitric acid, 8 64. the true work is so near 793 that calculated as to show that the reaction described is the chief one, and that the more perfect deoxidisation which may occur compensates for losses; how ever as it is not possible to w WE to near exhaustion as in this experiment, for practical purposes the atom should be taken as the equivalent instead of two-thirds.

137. It has been recommended to use salt instead of sulphuric acid, and the following trial was made under exactly the same conditions as the first; the current went np to fiV lasted 3fc hours instead of 7 gave a deposit of copper 4-13 Dnits and use of zinc 472 being a loss of oneeighth by local action. This proves, as might be expected, that the use of salt is bad economy, it takes no part in the reaction (so far as cost is concerned), except as a eondnetor, but the zinc is dissolved by the nitric acid transferred to it by electrolysis.

138. For practical use a much cheaper nitric acid may be obtained. Thus I use one of sp. gr. 1-4146 containing 76-4 atoms per lb., and costing threepence per lb., or -0393 of a penny per atom. Applying the results of the experiment to this value we have the cost of working nitric acid batteries thus :—

Cost of simple cell per unit -0471

Extra local action 14 per cent. = '0066

Nitric acid — 3 atom -0262 032S

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ThisshowB an excess of cost of one-eighth by using salt, and this excess would increase according as the cost of nitric acid per lb. or per unit exceeded the figure given. Adding to the first figures enough to bring the cost up to practical working, or 1 atom of acid per unit •0799 + 0131 = -0930 as the cost per unit as compared with the other forms of battery. This is somewhat under that of Darnells, but that is capable of reduction by causing the copper to be deposited in useful forms, while this is at its lowest; the real drawback, however, to nitric acid batteries is the escape of nitrous gases, which are unwholesome and very injurious to all metallic substances; where these can be avoided, and the trouble attending its use is of little m iment, the nitric acid cell is undoubtedly the most powerful and most advantageous source at prjfcot known from which to obtain a steady a id powerful current.

(To le ccn'iiived.)

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(Concluded from page 247.)

TURNING to tho subject of star-mist, under which head I include all orders of nebulre, I propose to deal but with a small proportion of the evidence I have collected to prove that none of the nebula! are external galaxies. That evidence has indeed become exceedingly voluminous. I Bhall dwell, therefore, on three points only. First, as to the distribution of the nebula):— They are not spread with any approach to uniformity over the heavens, but are gathered into streams and clusters. The one great law which characterises their distribution is an avoidance of the Milky Way and its neighbourhood. This peculiarity has strangely enough been regarded by astronomers as showing that there is no association between the nebulm and the sidereal system. They have forgotton that marked contrast is as clear a sign of association as marked resemblance, and has always been so regarded by logicians.

Secondly, there are in the southern heavens two well-marked streams of nebula). Each of these streams is associated with an equally welt. marked stream of stains. Each intermixed stream directs its course towards a Magellanic Cloud, one towards the Nubecula Minor, the other towards the Nubecula Major. To these groat clustors they flow, like rivers towards some mighty lake. And within these clusters, which are doubtless roughly spherical in form, there are found intermixed in wonderful profusion, stars, star clusters, and all the orders of nebula:. Can these coincidences be regarded as accidental? And if not accidental, is not the lesson they clearly teach us this, that nebula) form but portions of the sidereal system, associating themselves with stars on terms of equality (if one may so speak), even if single stars be not more important objects in the scale of creation, than these nebulous masses, which have been so long regarded as equalling, if not outvying, the sidereal system itself in extent?

The third point to whieh I wish to invite attention is the way in which in many nebula) stars of conciderable relative brightness, and belonging obviously to the sidereal system, are so associated with nebulous masses as to leave no doubt whatever that these masses really cling aronnd them. The association is in many instances far too marked to be regarded as the effect of accident. I Amongst other instancesf may be cited the nebula round the stars ci and e> in Orion. In this object two remarkable nebulous nodules centrally surround two double stars. Admitting the association here to be real (and no other explanation can reasonably be admitted), we are led to interesting conclusions respecting the whole of that wonderful nebulous region which surrounds the sword of Orion. We are led to believe that the other nebula) in that region are really associated with the fixed stars there; that it is not a mere coincidence, for instance, that the middle star in the belt of Orion is involved in nebula, or that the lowest star of the sword is similarly circumstanced. It is a legitimate inference from the evidence that all the nobula) in this region belong to one great nebulous g"oup, which extends its branches to these stars. As a mighty hand this nebulous region seems to gather the stars here into close association, showing us in a way there is no misinterpreting, that these stars form one system.

The nebnla round the strange variable star, Eta Argus, is another remarkable instance of this sort. More than two years ago I ventured to make two predictions about this object. The first was a tolerably safe one. I expressed my belief that the nebula would be found to be gaseous. After Mr. Huggins' discovery that the great Orion nebnla is gaseous, it was not difficult to see that the Argo nebula must also be so. At anv rate, this, has been established by Captain Herschel's spectroscopic researches. The other prediction was more venturesome. Sir John Herschcl, whose opinion on such pointB one would always prefer to share, had expressed his belief that the nebula lies far ont in space beyond the stars seen in the same field of view, t ventured to express the opinion that those stars are involved in the nebula. Lately there came news from Australia that Mr.

Le Saeur, with the great reflector erected at Melbourne, has found that tho nebula has changed largoly in shape since Sir John Herschel observed it. Mr. Le Sueur accordingly expressed his belief that the nebula lies nearer to us than the fixed stars seen in the same Hold of view. More lately, however, he has found that the star Eta Argus is shining with the light of burning hydrogen, and ho expresses his belief that the star has consumed the nebulous matter near it. Without agreeing with this view, I recognise in it a proof that Mr. Le Sueur now considers the nebula to be really associated with the stars around it. My belief is that as the star recovers its brilliancy, observation will show that the nebula in its immediate neighbourhood becomes brighter (ran? fainter through being consumed as fuel). In fact, I am disposed to regard the variations of the nebula as systematic, and due to orbital motions among its various portions around neighbouring ■tan.

As indicative of other laws of association bearing on the relations I have been dealing with, I may mention the circumstance that red stars and variable stars affect the neighbourhood of the Milky Way or of well-marked star-streams. The constellation Orion is singularly rich in objects of this class. It is here that the strange " variable " Betelgeux lies. At present this star shows no sign of variation, but a few years ago it exhibited remarkable changes. One is invited to believe that the star may have been carried by its proper motion into regions where there is a more uniform distribution of the material whence this orb recruits its fires. It may be that in the consideration of such causes of variation affecting our sun in long past ages a more satisfactory explanation than any yet obtained may be found of the problem geologists find so porplexing—the former existence of a tropical climate in places within the temperate zone, or even near the Arctic regions.*

It remains that I should exhibit the general results to which I have been led. It has seemed to many that my views tend largely to diminish our estimate of the extent of the sidereal system. The exact reverse is the case. According to accepted views there lie within the range of our most powerful telescopes, millions of millions of suns. According to mine, tho primary suns within the range of our telescopes must be counted by tens of thousands, or by hundreds of thousands

families of satellites; we see the rings of Saturn , in which minute sotellites must bo as the sands on the sea-shore for multitude; the wonderful zoneof asteroids ; myriads on myriads of comets: millions on millions of meteor systems, gathering more and more richly oround the sun, until in his neighbourhood they form the crown of glory which bursts into view when he is totally eclipsed. But wonderful as is the variety seen within the planetary system, the variety within the sidereal system is infinitely more„amazing. Besides the single suns, there are groups and systems and streams of primary suns; there are whole galaxies of minor orbs; there are clustering stellar aggregations, showing every variety of richness, of figure, and of distribution; there are all tho various forms of nebula;, resolvable and irresolvable, circular, elliptical, and spiral ; and lastly, there are irregular masses of luminous gas, clinging in fantastic convolutions aronnd stars and star-systems. Nor is it unsafe to assert that other forms and varieties of structure will yet be discovered, or that hundreds more exist which we may never hope to recognise.

But lastly, even more wonderful than the infinite variety of the sidereal system, is its amazing vitality. Instead of millions of inert masses, we see the whole heavens instinct with energy,—astir with busy life. The great masses of luminous vapour, though occupying countless, millions [of cubic miles of space, are moved by unknown forces like clouds before the summer breeze j star-mist is condensing into clnsters; star-clusters are forming into suns; streams and clusters of minor orbs are swayed by unknown attractive energies and primary snns singly or in'systems are pursuing their stately path through space, rejoicing as giants to run their course, extending on all sides the mighty arm of their attraction, gathering from ever new regions of space supplies of motive energy, to be transformed into the varions forms of force,—light, and heat, and electricity,—and distributed in lavish abundance to the worlds which circle round them.

Truly may I say, in conclusion, that whether we regard its vast extent, or its infinite variety,, or the amazing vitality which pervades its every portion, the sidereal system is of all the subjects man can study, the most imposing and the most stupendous. It isas a book full of mighty problems, —of problems which are as yet almost untouched by man, of problems which it might seem hope

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* The substance of a Lecture delivered by R. A. Proctor, B.A.. at the Royal Institution on May 6.

t Eight pictures of nebulas were exhibited in illustration of ton peculiarity.

numbers imply but that the space separating sun from sun is enormously groater than accepted theories would permit? And this increase implies an enormous inorease in the estimate we are to form of the vital energies of individual suns. For the vitality of a sun, if one may be permitted the expression, is measured not merely by the amount of matter over which it exercises control, but by the extent of space within which that matter is distributed. Take an orb a thousand times voster than our sun, and spread over its surface an amount of matter exceeding a thousandfold the combined mass of all the planets of the solar system :—So far as living force is concerned, the result is—nil. But distribute that matter throughout a vast space all round the orb —that orb becomes at once fit t> be the centre of a host of dependent worlds. Again, according to accepted theories, when the astronomer has succeeded in resolving the milky light of a portion of the galaxy into stars, he has in that direction, at any rate, reached the limits of the sidereal system. According to my views, what he has really done has been but to analyse a definite aggregation of stars—a mere corner of the great system. Yet once more. According to accepted views, thousands and thousands of galaxies, external to the sidereal system, can be seen with powerful telescopes. If I am right, the external star-systems lie far beyond the reach of the most powerful telescope man has yet been able to construct, insomuch that perchance the nearest of the outlying galaxies may lie a million times beyond the range even of the mighty mirror of the great Rosse telescope.

But this is little. Wonderful as is the extent of the sidereal system as thus viewed, even more wonderful is its infinite variety. We know how largely modern discoveries have increased our estimate of the complexity of the planetary system. Where the ancients recognised but a few planets, we now see, besides the planets, the

lems are given to him for solution, nnd he will solve them, whenever he dares attempt to decipher aright the records of that wondrous volume..

* Sir John Herschel long since pointed to the variation of our sun as a possible cause of such changes of terrestrial climute.

SCIENCE FOR THE YOUNG.*

By The Rev. E. Keenan, Clonoowes College.

( Continued from page 223.)

§ II.—Flexibility.

FLEXIBILITY is tho capability of bending without any permanent separation of the particles in a body. This is an important property, in consequence 'of practical questions which it involves.

No. I.—Laws.—A body in which the dimension of length is considerably greater than the other two dimensions, may be viewed as constituted by three sets of particles—the upper, the lower, and the middle. The conditions of these in a flexed body are the subject of the few but important laws of flexibility. A rod with wires passed through it, shows well, in an enlarged form, the meaning of the laws. When the wires oarry white beads the action is made still more evident, Fig. 37. Lead or some body thajt keeps the bent form, is the best material for the rod.

Law I. Tho tipper particles of a flexed body aro separated without destroying their molecular attraction. Hold tho wired rod, the wires perpendicular, bend the endsoonn, the wires diverge, forming an angle between each pair. The beads, as Fig. 38, represent the particles as separated by the action of bending.

N.B.—The terms upper and under, are not tobe taken in their ordinary sense only. For then the laws would refer to but one sort of flexion— centre raised up, ends bent down. Every flexed body has a convex and concave side. And in this sense are used the terms upper and under.

Law II. The lower particles of a flexed body are compressed. Look at the beads below («), they are close up, or perhaps overlapped.

* The copyright of this series of articles Is reserved by the Author.

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