ne thoroughly acquainted with the manufacture ive an opinion. If a soap powder were required, t use quilia bark.-GEORGE E. DAVIS. 3-COMMUNICATORS.-An "electric coil" is galvanic battery," a somewhat vague descrip: By communicator," I presume commutator is The coil would therefore seem to be an experi1 one. Any dry hard wood may be made available cheaper substitute for ivory or ebonite; but of a lower degree of insulation must be understood. found dry beach (such as is used by drapers which ribbons, &c., are wound) to answer very it may be rendered a very fair insulator by being aked in an oven and then, whilst still warm, into hot melted paraffine or stearine; when cold, raffine adhering should be scraped off. This will nd to answer very well, not only for the purpose but for coil-winding, &c.-SIGNUS. 9.1-COMMUNICATORS (QY. COMMUTATORS). Eggelre Reeb" means commutators, as I suppose he I believe he will find any dry hard wood answer 1 as ebonite. Ebonite is a very superior insulator, mpared with wood, and very valuable when asion of the current is high, as in coil machines, stance; but with a primary current I do not conit indispensable. I have a commutator that I with a cylinder of ebony which I had turned for a cost of about fourpence, and do not wish for a instrument of its kind. But why must the er be so large as 24in. by 1gin.? Surely lin. dia- and lin. or lin. in length must be large enougn ything?-GLAUPHUS.

0.3-ALLOY.-As "Hammersman" does not say ard he wishes the alloy, or for what purpose, it is alt fto supply him with the information which I be glad to do. If only lead, tin and zinc are the s available, the difficulty is increased, as he must xpect iron produced out of them. An alloy of four lead and one of antimony is a near approach to it, as colour, and the conditons under which it may oken, and its hardness,-STEWART WILLIAMSON. 21.)-SAFETY VALVES.-The diameter of a valve E given, multiply it by itself and the produce by and you will have the area in inches if the diaris in inches. Do you mean to weight the valve by d weight inside the boiler, or by a lever and weight de? as this materially affects a complete answer our query.-STEWART WILLIAMSON. 527.

VERTICAL DRILLS.-In answer to P. J.," I forgot to state that the vertical drill that at the sketch of was for drilling the edges of plates anks; therefore, the frame would support itself

ing the time the drill was in use, owing to the prese of the screw, but the addition of two or four eyes C) cast on the frame would have the desired effect; y little extra trouble would make the required addins.-Josн. MOSELEY.

6529.1-ATMOSPHERIC CHURN.-The atmospheric irn is a cylinder of tin into which fits a concave lid with a hole in the centre. The plunger-rod works through this hole, and is a tin tube having a valve fixed at the top, opening downwards; the handles are also fixed on the rod, at right angles to it. The plunger is a round piece of metal with holes in it. The churn is held while in use by two pieces of wood, with a semi-circular piece cut out of each, into which the churn fits; they are held together by a nut and bolt. The churn is half filled with cream, the operator places himself on the wood stand and raises the plunger, and thus exhausting the air in the hollow plungerrod, air rushes in through the valve to fill the vacuum, and on

head" is aware that there must be a spring-catch in it to fit into the nicks in the pendulum and so regulate the time. The time the metronome will go depends of course on the rate at which it is beating, and therefore instrument, I beg to refer "Thickhead" to 5694, or to no rule can be laid down. For the means of testing his let. 945.-BEACON LOUGH.

[6541.]-RAINBOW.-With the fear of "E. L. G." before me, I venture to assure "J. K. P." that there is not only no reason why circular rainbows should not be seen, provided the sun, spectator, and the drops are in the required position; but such circles have been seen from situations which were as balloon-like as possible. The circle underneath would be of course most difficult to see, from the clouds which caused the rain obscuring the sun. A bow over the surface of the sea, horizontal, was some time ago described and illustrated in the ENGLISH MECHANIC.-M. PARIS.

[6541.] RAINBOW.-There seems nothing to prevent persons in a balloon-car seeing the primary and secondary bows, as "J. K. P." suggests, provided the cloud canopy be limited enough, and sun low enough to illuminate the upper drops, otherwise they are more likely to see only the lower part of each circle. In some books-even in Brewster-I find the mistake that complete circular bows might be seen from a precipice or mountain, which is quite impossible, as the lower drops must be reached by rays passing under the spectator. The sight is not possible from even the slenderest spire-top, but only from a balloon, as "J. K. P." has observed.-E. L. G.

[6548.]-OXYGEN GAS.-If Thomas Lewis requires oxygen gas for the lime light, he should heat in a copper or iron retort a mixture of three parts by weight of chlorate of potash and one part black oxide of manganese. As the gas is evolved it is passed by means of a flexible tube to the purifier, a vessel half filled with water, into which the pipe from the retort dips. The gas bubbles through the water to the upper part of the purifier, whence it is conducted by another pipe to the gas bag. Care must be taken to disconnect the retort from the smaller scale oxygen may be made from the same purifier before withdrawing the source of heat. On a materials in a glass retort, or flask fitted with a bent tube passing through a tightly fitted cork, and dipping into water. The gas may then be collected in a jar or bottle, filled with water and inverted with the mouth below the surface, over the end of the tube.-L.

[6576.]-VESTIGES OF CREATION.-I propose only to touch on some of the questions under this head. From worlds, I am inclined to believe that he must be the a study of Montague Phillips' work on the plurality of author of "Vestiges of Creation." As to another of Omega's questions, the views of Darwin and Huxley are (severally) quite distinct from the doctrines advocated in the "Vestiges." I do not remember anything in the "Vestiges" resembling Prof. Huxley's special biological views. The author of the "Vestiges" (I speak from memory) while dwelling not unfavourably on Lamarck's view that volition influenced by outward circumstances is a principal cause of changes in species, advocates specially the influences due to the long or short continuance of foetation. Darwin and Wallace, as we know, assign the primary influence to natural selection depending on the survival of the fittest. The "Vestiges" dealt with astronomical theories, some of which can hardly be said to have survived. As to the geological theories in the "Vestiges," and again as to the biological questions asked by " Omega," I of course venture no opinion.-RICHARD A. PROCTOR. [6630.]-THE GAMMA FUNCTION.- This name is given to the second Eulerian integral, or

and is represented thus: r (n). For positive integral values r (n) is the same as factorial (n-1), that is (n-1) (n-2).... 3. 2. 1. The function is an important one; but the subject is somewhat abtruse, and with the function, I do not feel justified in sending until I know definitely what " B. C. E. B." wants to do either an explanation of its nature or worked examples. R. A. PROCTOR.

(B) 4-14 x + x = 11-49=-38

x4-14 x2 + x + 38 = 0

From this equation we get = 2,.. y = 7-x2=7-4

V11 V9 = = +3.

[6643.]-PROJECTILES.-Can any one tell me what is the greatest distance that a projectile has been thrown from a cannon, with its weight, ape, bore of cannon, and maker's name?-KENWICK.

[6644.]-DIFFERENTIAL GALVANOMETER-Will any reader give a full description of the "differential galvanometer," with diagram and information as to the different kinds of testing?-A. H. B.

1

[6645.] SIZING CLOCK PINIONS.- Mr. Henry Chapman having so kindly given us such a lucid and haps he or some other of our readers would kindly decorrect description of the dead-beat escapement, perscribe the method for correctly sizing clock pinions to wheels ordinary and lantern, and enlighten numerous readers, especially-MIDDLESBRO.

[6646.]-ANALYSIS OF IRON AND STEEL.-Will "Sigma," or "Urban" be kind enough to give a short description of the usual method of analyzing iron and steel for carbon and silicon (quantitatively), and if still not too much for sulphur and phosphorus. If either of the above gentlemen will comply with this request, it will doubtless prove profitable to many fellow subscribers who are steel and iron workers, and confer a lasting benefit upon-FERRICUM.

reader of the ENGLISH MECHANIC state the simplest [6647.]-BEET-ROOT SUGAR. Will some kind and best method of extracting sugar from beet-root, so as to be suitable for ordinary household purposes ?HOME PRODUCE.

[6648.]-TWO HORSE-POWER HORIZONTAL ENGINE.-Would any reader give the sizes of the following parts of a two h.p. horizontal engine and boiler, or a rule for finding the same: viz., cylinder, slidevalve steam ports, connecting rod, slide bars, eccentrics, crank, reversing gear, governors, fly-wheel, and bed?W. F. W.

[6649.]-DYEING KID BOOTS.-Can any one inform me how to dye white kid boots or shoes black?H. P. T.

[6650.]-BRASS INSTRUMENTS.-Will some kind reader inform me how to take slides out of brass inand therefore adhere too firmly to draw out without struments that have not been in use for some months, starting the joints? Also how to make a new joint (as solder leaves a mark and does not hold well), and what material used? Also how I can take out the indentations made in brass instrument by falling and otherwise? A detailed account how to do the above, with what tools and materials used will greatly oblige.-COUNTRY BAND MASTER.

[6651.]-WINDMILL POWER.-I should be obliged by some of your readers informing me through the well 100ft. deep to lift water to a cistern in the roof of ENGLISH MECHANIC What size pump should be put in a a house 40ft. high, and supply one jet of ornamental water? Also whether a 2in. drawing lift to surface emptying in a tank sufficiently high to supply the garden fountain jet, and to the rod of the drawing lift a small plunger to force a supply of water to the house cistern would not be most economical? (See 6633.)-F. GUILD

FORD

[6652.]-DRILLING WROUGHT-IRON.-Will any of your numerous readers inform me if there is any substi tute for oil used at the drilling machine when drilling wrought-iron? I have several drills at work continually and find the quantity of oil used is very great.L. L. W.

[6653.] LEKEYO ISLES. Would some brother reader kindly inform me where these islands are situated, and whether there is another name for them, as I cannot find an account of them anywhere? Perhaps some one will be good enough to give a few particulars relative to them, as to their products, imports, exports longitude. I feel assured it will be useful to many. and population; also in what degree of latitude and also want to know a few particulars relative to Dr. Thomas Burnett (author of "The Sacred Theory of the Earth"), such as place of birth and death, &c., and oblige -S. B. ROSEVEAR.

reader be kind enough to inform me how to make a [6654.]-CHEAP ENLARGING CAMERA.-Will any cheap enlarging camera ?-AMATEUR.

[6655.]-OXYGEN BURNING IN HYDROGEN.-Will any of your readers state whether a jet of oxygen will burn in an atmosphere of hydrogen, and if so, describe the mode of operation.-THETA.

[6656.1-ELECTRO-MAGNETS, ETC.-I beg to thank Mr. Tonkes for his reply to my first query (6289, 6432), and to ask him to be kind enough to reply to the third. Also state if the wire on what we may term the legs in the imitation Joule's magnet is crossed from one to the other as in the ordinary magnet, or if the wire is coiled round the tube from the opening on one side to the opening on the other side; or if a space is left opfastened to a board; would it be more powerful if the posite the opening without wire, so that it may be tube was 8in. long? Please state when the details were given in our journal, and oblige.-SNATCHBLOCK.

[6657.]-CARBOLIC ACID AS A DISINFECTANT.-Would some chemical correspondent be kind enough to state how and in what quantities the above should be used, and if the health of those in the house would be affected by using it too strong. Also the price, and or liquid? By so doing, I have no doubt they will benefit many others besides.-SNATCHBLOCK.

two equations. First

Second

reduce the weight until

correct.-R. COOPER. [6532]-METRONOME.-I would recommend "Thick

head" to get some suitable person to make a weight and adjust his metronome, for I should say he will find it rather troublesome. The following are the particulars of the weight on my instrument (a Maelzel):-One side measures 85 of an inch; other two 7; the fourth 325; it is about 125 of an inch thick and weighs 110 grains; the longest side is placed at the top. Doubtless"Thick.

12+y=a (2) y2 + x = b

was not my own but the editor's. I had had the four cells in question in constant use for more than two years, and had used a few for a year or two before for electrotyping small articles; so that I should not have been justified in calling the arrangement new. Will "Signus" kindly describe Leclanche's manganese battery, and oblige me, among, no doubt, many others of your readers? I should also like to know how to utilize the deposit in my arrangement of Daniell's battery. JACOBUS.

[6660.]-SAFETY VALVE.-Seeing R. Brumhall's answer to query 6869, by "Young Hand," would it be asking too much of him, if in his sketch of safety valve he reckons the lever to be 42in. in length, and the ball 52lb. in weight. If so, must I measure from the peg holding down the valve, or from the extreme end of the lever ?-SHROPSHIRE.

[6661.]-MULE SPINDLES.-Will some of our cotton spinning friends say what is the greatest speed that mule spindles, 15 in. in length, spinning from 12's to 24's weft, may be driven without injury; and also how many draws per minute Walker and Hacking's stripping mules, of 600 and 800 spindles, and 62in. stretch, may be run without injury.-JACOBUS.

[6662.]-COPPER LACQUER.-Can any of my brother readers inform me how to make and use a brown or copper lacquer ?-A. SMITH.

[6663.] ANILINE SULPHATE.-Will any kind reader oblige me with a formula for the manufacture of aniline sulphate ?-J. T. SANDELL.

[6664.]-NITRATE OF TIN.-Will any of my fellowreaders inform me what is the composition of the selution used by dyers, under the name of nitrate of tin? I have always understood that tin was insoluble in nitric acid alone, in consequence of its being oxidized to metastannic acid, Sng O5 H010. I am aware that this is capable of combining with hydrochloric acid, and is then soluble in water. But I am told that some dyers use nothing but nitric acid and tin in making their spirits. Also, I should be thankful for any information as to the manufacture and composition of other solutions used by dyers, such as royal blue finishing spirits, muriate of tin, &c., and I have no doubt many would be interested in the subject. I have read Slater's manual, recently published, which, though excellent in some things, is very ambiguous as to the various solutions of tin. I should like to know if it would be better for manufacturing chemists to send out, or for dyers to make, some regular compound of tin, either stannous or stannic chloride, and if other acids are required, the dyer could add them at discretion, instead of being, as he is at present, almost entirely at the mercy of the manufacturer. I am convinced that amongst dyers a profound ignorance prevails on this subject, and a little information would oblige.-UN TEINTURIER.

(6665.]-CASELLI'S INSTRUMENT.-Might I beg some "Telegraph" worker to give some particulars of Caselli's or similar instrument, showing particularly the means used to regulate the motion of paper, and the best mixture for decomposing, especially as regards quickness of action? Your correspondent cannot find a battery powerful enough to make a mark sufficiently quickly-say 10 to 20 distinct dots per second (owing, possibly, to some other defect ?) He has tried Halse's with platinized carbon and sulphate of mercury (six cells), &c. A description, too, of the type-printing telegraph would oblige.-M. A. CANTAB.

[6666.]-THERMOMETER SCALE.-I have a thermometer scale (the tube has long been lost) on an old barometer (probably more than 100 years old), the scale is 21in. long, and the range is 95°. The oddest thing about it is, that the scale commences at 90°, the limit of "extreme cold," as it is called, and rises to 5° above 0, which is marked "extreme heat," or rather "extreme hot" maker's name, Samuel Moore. Now if any brother reader can give me any information as to the probable age of the instrument, and the liquid used in the tube, he will much oblige.-No. 170.

[6667.]-LECLANCHE'S BATTERY.-TO" SIGNUS." -I, for one, should be very glad to hear details of the construction, and of "Signus's" experience, of the working of Leclanché's manganese cells.-H. H. G.

[6668.]-STORM GLASS.-I have recently endeavoured to make one of those reliable weather prognostics, but unfortunately failed. During the last three weeks nothing else has appeared in the tube but a quantity of small particles like stars, which adhere to the sides of the glass and are perfectly stationary, whilst the thick substance has settled closely at the bottom, and a little dirt has by some means got in and settled upon it. The mouth of the tube is corked, as the alcohol evaporates when a perforated skin is tied over it. It is composed of lb. of alcohol; oz. of camphor; 1 drachm of muriate of ammonia; 1 drachm of nitrate of potash; the whole enclosed in a tube 18in. in length by in. diameter. If any of our numerous readers will kindly point out my error, I shall feel obliged to them.-IN DIFFI

CULTY.

"Sigma [6669.] ELECTRICAL. - Will "1 or Mr. Tonkes kindly give me information upon the following?

-I am about making a coil, to be like those exhibited at public gardens, &c., and want to use both primary and secondary currents; but as both terminals of the primary are connected with the battery, I don't quite see how to use that current. Whilst using the primary, what becomes of the induced current in the secondary? Does it not injure the coil? Will not aluminium foil do instead of platinum? What is meant by connecting batteries together "intensity" and "quantity" fashion, and in what cases ought they to be so used? A clear answer to this question will be of benefit to hundreds besides myself.-PYRO.

[6670.]-CHROMEIDOSCOPE.-Will one of our kind friends describe a chromeidoscope and its use ?-WM. SHILLINGLANE.

[6671.]-TRANSPOSITION.-I wish to avail myself of "H. G. W. B.'s" kind offer. I play two instruments-the English concertina, and the Northumberland or sund pipes. The pipes is my favourite instrument for lively music, the concertina for that of a more grave or solemn class. The scale of the pipes is from D below the line to B above the line, and can be played only in the key of G or D. The drones are set to the ke hote and the

fifth, and an octave below the key-note, which forms a sort of imperfect sustained harmony. I often meet with tunes that are not in the suitable keys, and have them to transpose into a suitable key; but I sometimes meet with tunes that will not come within the compass of the instrument; I can, perhaps, get the first strain in the key of G all right, but the second straiu will go too low or too high, so that it is beyond the compass of the instrument; in this case, would it be legitimate to write the second strain in the key of D, or to write part of it in the key of G and modulate the part beyond the Compass of the instrument into the key of D? Would "H. G. W. B." be kind enough to tell me if there is any strict rule for this kind of thing, or is it entirely depen. for a given instrument? Can he give me the title of dent on the taste of the person who arranges the music any work that would assist me in this case? I generally arrange the tunes to suit my own taste, but I do not know whether I do it in the best or proper way. PIPES.

[6672.]-EXPANSION VALVE.-My boiler pressure will range from 501b., required to drive my engine, to 90 or 1001b. for other purposes, this higher pressure being required for a few hours per day only. Will some one kindly recommend, from experience, a simple and effective variable expansion valve to meet the case? I scarcely expect to find one controlled by governors acting through a range of 50lb,; but I shall be well satisfied with one which can be adjusted by the engineer. The throttle valve will have enough to do to regulate speed when machines are thrown on and off, and a stop valve or a diminishing valve is but a clumsy contrivance, and would not be as economical as an expansion valve. Engine 6 to 8 horse-power will run at least 60 revolutions per minute. Again, should I reduce my cylinder an inch in diameter, and work constantly at 100lb. pressure? To save fuel is a great object to me. -R.G.

[6673.]-BRAKE FOR TWO-WHEELED TRAP.Could any reader tell me what kind of a brake to use on a two-wheeled trap, so that instead of the weight being thrown on the horse's back, to be made light on or taken off? All brakes that I have seen throw the full weight as described above.-G. T. B.

[6674.]-FITTING BED TO LATHE.-What is the best kind of iron to case a wooden bed with? Will angle would suit the job better?-SAMUEL LEXICON. iron answer the purpose, or is there any other kind that

[6675.]-BRASS CASTING.-Will some correspondent kindly inform me of the best mixture for brass that will stand a great amount of pressure, such as is used for brass steps and blocks, &c.; also how are the beautiful colours produced which appear on some brass castings?-MONTHLY SUBSCRIBER.

[6676.]-SWISS WATCHMAKING-Is the crysalin or crystalin such as the Geneva watchmakers use to jewel their watches, as hard, and does it wear as well as the diamond for that purpose ?-X. T. Z.

[6677.]—FOUR-JAWED CHUCK.-Will "J. K. P." kindly help me? I am going to make a four-jawed chuck for my lathe, and should be very grateful if he would kindly tell me the best way and pattern for it. If he has a drawing I should be very grateful for the loan of it.-H. H. H.

[6678.]-THE ECLIPSE.-"Cireb" (let. 1364), in No. 307, gives us one of his photos of the late eclipse. I am sure many would be interested and much obliged to him if he would give us a full description of the apparatus used and mode of using it, in obtaining solar photographs. I should much like to know whether he has been successful in taking pictures of the sun showing spots, &c. I had thought that the time of exposure was a small fraction of a second. In that case surely clockwork is not required ?-ALGOL.

length moves about a point placed 3in. from one ex[6679.]-PROBLEMS.-(1). A straight bar 13in. in tremity, a force of 30lb. acts at the end of the longer arm, but inclined to it at an angle of 45°. What force acting at the shorter arm at an angle of 30° will preserve equilibrium? Answer, 141lb. (2). A circular plate, whose radius is 20in., is movable about its centre C in a vertical plane; from two points A and B in the circumference, 90 apart, weights of 18 and 24lb. respectively, are suspended by cords. Find the distance of the lighter weight above or below the horizontal line through C when the plate is at rest. Answer, 12in. Please use Euclid only, and draw figures.-PHILOS.

[6680.]-STRAIGHTENING WIRE.-What is the best and simplest means of straightening No. 4 wire iron? Without stretching there is a simple way of doing it, which is used by wire workers. Sketch or description would oblige-J. B. A.

[6681.]

SOLDER FOR BRITANNIA METAL.

Would Jack of all Trades" state the best composition of solder for the Britannia metal goods, very thin?J. B. A,

[6682.1-CALLAUD'S BATTERY.-I have a Callaud's battery, and the only bad thing in it is the constant falling of the sulphate of zinc, which makes the current feeble. How can the falling be prevented ?—E. A. [6683.]—HYDRAULIC PACKING.-What size should the groove be in a cylinder for an hydraulic press? I have made one for a 5" ram, but I always burst the leather in cutting of it. The cup is 13" X 8" What kind of leather is used?-HYDRAULIC.

[6688.]-COVERING FOR STEAM BOILER E-K some experienced reader will kindly answer the once, it will greatly oblige, as the writer is about 1) something of the kind in a remote district. White wanted is not felt, but a substance composed principl of the refuse from flax-mills, mixed up with composition into a paste and applied in the sta to the hot steam boiler or pipes, which immediately bakes it hard, and, as I have had experience, is the preventor of radiation I know. Any who rep confer a great favour on-ONE IN NEED.

[6639.1-RIBAND OF BRUGES.-How is it medal

E. A.

have a slide-rest for a 6in. back-gear lathe, and we [6690.]-SLIDE-REST.-TO "J. K. P."--I vid feel obliged if our able correspondent would say it short or cross slide ought to be below the long sid in the lathe figured on p. 111, No. 994, Vol. XIL Cunliffe, Manchester. I would not like to attempt fitting of long slide with projecting fillets which mos good lathe rests have. Also could I manage to pa the castings on a morticing machine table, which of course, two slides, by having a strong bar bolle standard to carry tool-holder, and would the tooth require to be hinged so as to clear work on the ro stroke. The table would have about 14in. traverse If "J. K. P." would oblige by a sketch of shem for plain iron turning, &c., to scale or the sizes mirad it would be of great service to many of our resis As the slide rests shown in "The Lathe and Its U are perspective views, and are mostly for aram work, an outline drawing ought to do.-J. 8.

[6691.]-COCOA.-Which is the best method of pre paring the bean for a beverage; can it also be prepares as an edible for ordinary household use 7-A COSTANT READER.

[6692.]-ELECTRIC BELLS.-I wish to erect dates bells between twe businesses distant apart 500 yards! have a 10-cell Leclanche battery, and I wish to kosi will work the two bells from one battery by car the wire the whole circuit; also if the studs are wel right places? Must both studs cut the current; ü «. how will the current be complete by the pressure f one stud?-G. HARVEY.

[6693.]-PARSON'S WHITE BRASS.-Will see inform me anything of Parson's white brass, its position, or, if a patent article, where it can be tained? Any information on the point will be resi thankfully.-CROMWELL.

[6694.]-CURING BACON.--Would any of the Esc MECHANIC readers kindly inform me how bacon is in large provision stores; in fact, give me soten pits ral hints on the provision business as done in lago cerns?-J. F. G.

[6695.]-ARTILLERY.-How are the heavy be? rather bolts for the modern guns rammed home guns are muzzle-loaders and rifled, and the st

-AN OLD NAVAL OFFICER.

[6696.]-MOUNTING MICROSCOPIC OBJECTSTO "H. P. H."-Many thanks to "H. P. H. reply to my query (6435), but would be enlighten A one or two points in his method of mounting? I be glad to know, in the first place, what is the f arsenic used with dilute alcohol. Will he als his reason for heating the glycerine after moving this medium, unlike Čanada balsam, is never re any thicker thereby; on the contrary, the app of heat in some cases would be more likely to exc reappearance of air-bubbles than otherwise

SCOPIST.

[6697.]-ARITHMETIC FOR THE BLINDthanks to "Bernardin" and other kind friends wh replied to the above query (6121). Could M. Pat. thinks handling lead would be injurious to be recommend any other material which would 22. better? Please also give brief hints how to " figures. Would gutta percha answer the purpesa! I here mention that I find "our" MECHANIC Very esting and useful, and that my son, who is unable t for himself, is anxious to hear it read every w soon as it comes to hand.—C. F.

[6698.] HORSE POWER. Would some th reader please to inform me the horse-power of e gine with the following dimensions:-Cylinder. pressure, 80lb.; speed, 75 per minute; stroke, a BEN. LODDY.

[6699.]-INDUCTION COIL BATTERY, Ebe glad it "Sigma" or some other ader will me upon the following points:-1. How many

pista f Bunsen's battery may I safely use with a coil sade by sin. Primary Coil. 3 layers No. 18 cotton vanished cartridge paper, core 6in. long by in. copper wire, divided from the core by 8 or 4 lavers small iron wires. Secondary Coil-About 10.1 86 silk covered and varnished copper wire, each l insulated with two coats of varnish, varnished silk and two layers of gutta perchs except on the 1st and 2nd layers, which are whe silk. Between primary and secondary coil are the layers of well-varnished silk, and two coats of allowed to dry hard before covering with secondary have some in my possession? Brdly. Can tart copper wire, No. 36, improve the coil (if added t 2ndly. Would some cotton cove red and van fumes be got rid of when using the Bunsen's tutor without impairing the battery, with regard to its p for working the coil; if so, how ?-CURRENT.

[6700.]-RE-BRONZING LEATHER-1 have beautiful embosses and other fancy articles in kid, and morocco leather, which have become so discoloured.

Will any kind reader tell me how i

re-bronze them ?-DODO.

KETTLE. Will some one inform me how to de [6702.-[DEODORIZING SMOKE FROM VARNIS the smoke from a varnish kettle ?-G. KXIST.

1

3

8.)-MUSIC.-H. G. W. B." (let. 1872, p. 494), y offers to answer questions in music to the best of bility. Can he, or some other correspondent help A friend of mine has a "Breeches Bible," date a prayer-book of the same date is bound up with lost, if not all, the metrical psalms have a melody ed to them. I send a copy of the first line of four em. The first note in each case is evidently the ote? Is this denoted in the signature; if so, how; a what keys are these examples set? As far as I been able to find out by examining a great number tunes, the mark something like the flat in modern c is in most cases placed on the minor third below ey-note.-H. T. W.

04.] HUGHES'S TYPE - PRINTING TELEPH.-Can any one give me a description of this inment, or tell me when it was patented, as I have hed at the Patent Office and failed to find it ?-Z.

05.]-LATHE MANDREL.- I wish to thank K. P." for his kind answer and attention to my fons on lathe mandrel, but without wishing to ss too much upon his time and patience would yet me favour of another answer. 1st. I will take his e and decide upon a 6in. instead of a 7in. lathe, a leading screw of in. pitch x 14in. diameter. I wish to know the distance from centre to centre ctively of mandrel to back spindle and mandrel to ng screw, and size and form of wheel plate. 3rd. we measured the drawings of the 5in. Whitworth , but cannot get the measurement I want with degree of certainty, as only the thickness of a line vs it out very much after being multiplied five or imes. I hope he will forgive me for saying that the avings are scarcely to be depended upon, that of ast headstock representing a 5in. lathe, and the ing poppet a 6in, or 6 in. ditto. I shall therefore be if he can oblige me with the measurement in es of, say, the working collar surfaces of front and x cones, diameter and depth or length of each with side and thickness of the planed top of bed; all the I can manage myself.-D. W.

2

MECHANIC would give me a description, and if possible, a sketch of an apparatus for turning them. It should be capable of doing various descriptions of twistings in diameters from ore inch to five inches, and of various lengths.-A DUBLIN SUBSCRIBER.

[6716.]-ELECTROTYPING.-With other duties I have had charge of a printing press belonging to the establishment with which I am connected. The founts of type being small in quantity, and having certain work to perform at regular intervals, I am often labouring under great disadvantage by being compelled to distribute the type in the "formes " belonging to the regular work, in order to print odd jobs. Now so as to avoid the disadvantage I am thus brought to, I have tried often to electrotype those formes, and have in that succeeded, but have never been able to mount such electrotypes on the metal blocks I have prepared for that purpose. The electrotypes-copper-would never adhere to the metal blocks, or where there has been adhesion the electrotype has warped, and has consequently been useless for printing from. May I beg you will kindly give me such information as will enable me to effectually solder the copper copies I make to the type-metal blocks.-P.S.-The press I have had charge of is not in England or in any country where such work as I wish information on can be put out; and as I return shortly I should like to be able to do such work as I have stated on my return?-A PRACTICAL INQUIRER.

[6717.]-SOFTENING WELL WATER.-Should feel greatly obliged if any of your numerous correspondents can give me details of Clark's, or any other process for softening well water for domestic use. Water from sandbed 30ft. below surface; we lift it 12ft. above the ground, into a large cistern; the only fault is its hardness.-W. HICKLIN.

[6718.]-PRACTICAL GEOMETRY.-Would any of your scientific correspondents' kindly inform me how to apply geometry practically. For instance, how to measure with compasses, without a micrometer, and get exactly, 63661 of an inch? I wish to make a circle of 2 inches exact, and I calculate that the above is the proper diameter, but how to measure it on actual work, I am at a loss.-L. O. W.

706.]-THE EQUAL WEIGHT OF ULTIMATE TICLES.-Sir Isaac Newton has shown upon the osition that the ultimate particles of bodies are lly heavy that the absolute refractive power is l to the excess of the square of the index of the retion above unity divided by the specific gravity of bove. Can any of our optical readers give me ton's demonstration of the above?-Vox. 707.]-WHITWORTH'S LATHE.-I am fitting up a head stock for my lathe on the principle of the one ribed by "J. K. P." (let. 1166, p. 897); but there are or two things that I would very much like him to ain a little more clearly. Are the two nuts marked "for tightening up the collar "e"? If so, what vents the pulley from coming to the left? Also, t is the diameter of the front and rear collars ? uld the mandrel made of scrap iron, have steel ar for the bearings working into the head-stock; will it be better made of the best cast steel unlened? Does not the mortice-hole through the [6721.]-FLUID LENSES.-TO MR. WRAY.-Having drel weaken it ?-D. S. B. F. been informed Mr. Wray is a reader of the ENGLISH MECHANIC-I think he has formerly also been a contri1708.3-GILDING WATCHWORK. - How is the butor-and seeing that "Hyperion" (p. 472) states he ing done on watchwork?-I. T. (Mr. Wray) has great practical experience with finid lenses, I most respectfully suggest that he would confer who desire the improvement of refracting telescopes if a great favour on myself and my many fellow readers he would kindly inform us how refractors with fluid intercepting concave lenses perform, and to what extent he was able to reduce the lengths of these tubes below the lengths required when flint concaves close to their convex lenses are employed? I can well understand there is little temptation to construct double concaves of bisulphide of carbon for telescopes of moderate focal length and aperture (say 6in. and 12ft. focus), and that, having two additional surfaces to grind and polish, instruments; but with very large apertures (say from there could be no pecuniary saving by doing it for small 10in. to 30in.) I suspect the fluid lens would, from its comparatively small size, cost less than a flint concave, and I think its dispersive power be found more equal than that of glass; but Mr. Wray's opinion on this question is the desideratum. I trust Mr. Wray will not be offended by the liberty I take in addressing to him the above questions, for which the importance of the subject is my only excuse; but it is so natural for us when we want "more light" to apply to those who have obtained it by experience-that best of teachers. I should also be obliged by Mr. Wray's address.-THE HARMONIOUS BLACKSMITH.

[6719.]-PROBLEM.-Given the base and the height of a triangle, and the difference of the angles at the base, to find the opposite angle.-A BELGIAN.

[6720.] SPEAKING TUBES.- We have three lengths of gutta-percha tubing, ĝin. diameter and about 50 yards long; the ends are connected, as usual, to a piece of coiled wire covered with worsted braid in. diameter, and whistles at each end. They are carried up to the ceiling of a lofty shop from 4ft. off ground-line, and then drops at other end to about same height. There are several other bends in same necessitated by the formation of shop. Now, the trouble is we can easily sound the whistles but cannot make our voices heard. What is the matter? The help of our friends is requested.-ARMLEYITE.

3709.J-MALLEABLE IRON GIRDER,-Will some der show me how t design a malleable iron girder a span of 60ft., to support a travelling weight of two 3?-M. R.

7101-CLEANING CRUDE OIL TANK.-1 have a er, formerly used as a crude oil tank, made from le. Would any reader inform me how to clean all oil out of it, as I intend using it as a steam boiler?-1711.]-OXYGEN GAS.-How many cubic feet of gen gas ought to be obtained from a mixture comed of lb. of chlorate of potash in crystals, and 1lb. powdered black oxide of manganese ?-EDWARD

JAR.

1712.]-HYDRAULIC LIFTING JACK.-Can any ow reader kindly state the exact time required for a raulic lifting jack to run out or lift its highest, hely, 7in.; lifting power, 2 or 3 tons.-WAREHOUSE

3713.1-HEATING BY PARAFFINE LAMP.-I have de a small hot water apparatus to sffine, but cannot get the lamp to burn without be heated by oking. It is an ordinary lamp, with a tin chimney ened at the top, to allow of the funnel-shaped boiler rly touching the flame. Will some one kindly help [6722.]-PIANOFORTE CONSTRUCTION. TO J. JENKINSON.-Will J. Jenkinson be so kind as to inform

2--C. R.

6714.)-ASTRONOMICAL-Could "F. R.A.S.," or any er of your astronomical subscribers kindly answer following? Give the degree and minute of the ecliptic, which the eight primary planets are in their apogee extreme distance from the sun. I have consulted ny common books on astronomy but cannot find it en.-BAZILICUS.

715.]-LATHE APPLIANCE FOR TWISTING.-I ve, at various times, twistings in wood, and the time kes to cut them by hand is rather more than I can veniently devote to it. I would be glad if some of able and talented contributors to the ENGLISH

purposes, we may regard them as being parts of two sonnding-boards, which is = duplicating the treble of the piano.-THE HARMONIOUS BLACKSMITH.

[6723.] ROOK RIFLES.-What is the best make of the modern rook rifles; and could a moderate shot hit an object of the size of a rook at 150 yards distance with one?-HESITATING.

[6724.]-SILVER MEDAL.-Would any of our readers kindly inform me of the value of the medal with the following inscription; it is of silver and considerably larger than a crown piece:-Obverse. Catharina. D.G. Mag. Bri. Fran. et. Hiber. Regina. Reverse-Pietate. insignis.-H. C. C.

[6725.]-MACHINE FOR RULING PAPER.-Would any of my fellow readers kindly explain the machine for ruling paper? A drawing would oblige-J. H. S.

[6726.]-MOUNTING MICROSCOPIC OBJECTS.-In mounting with Canada balsam, I find that objects have a great tendency to become displaced from the centre of the slide; first, when the balsam is applied, and again when the thin glass cover is being put on. If one of your able correspondents would kindly explain how this difficulty can be avoided, the information would be thankfully received. It has been suggested to me that the object should in the first place be attached to the slide by a drop of balsam being placed underneath it.J. H.

[6727.]-SOAP PLAISTER.-Will some kind reader inform me how to make soap plaister for corns? the same as the dark-coloured sold by chemists, as I wish to add another simple ingredient to it for the cure of corns. HANTS FARMER.

[6728.]-BOOKBINDING.-GILDING ON CLOTH.Will" A Practical Bookbinder" or any reader inform me of the method of gilding on cloth, as I have frequently tried, but cannot succeed, though I can do it very well on leather ?-PORTSMOUTH AMATEUR.

[6729.]-PHOSPHATE OF LIME.-I shall be glad if Mr. Davis or " Urban" will kindly give me particulars of the best method for analysing quantitatively phosphate of lime. Also its uses.-P. J.

[6730.]-POWER OF FIRE-ARMS.-What is the reason that a revolver carries a bullet to a greater distance in proportion to its size, and the length of the barrel, than that of a rifle? Both of them are grooved, and a long barrel either in rifle or gun is generally supposed to carry further. Is it because the steel in the barrel of revolvers generally is harder, or of different expansive power to rifles? Or what is the reason?-A GRATEFUL SUBSCRIBER.

[6781.]-VARNISH POR WOODCUTS.-Will any one kindly inform me what is the proper varnish for wood cuts (cartoons from Punch, &c.), and is the varnish to be applied before or after the print is mounted ?-LIVERPOOL SUBSCRIBER,

[6732.]-WIDTH OF STEAM PORTS.-What width of steam ports would be required for 2in. engine, 4in. stroke, and the distance between them; also the area of each port; also the lap and lead of the valves; also any information regarding the size of cam and link, &c.? A sketch would much oblige.-STEAM.

[6733.]-BLEACHING BONE.-Will any one inform me how I can bleach bone; that is, to take out the bad coloured marks? Also the best way of getting grease out of bone ?-J. TWIST.

[6784.]-TOOL FOR CUTTING JACQUARD PINS.Will any reader of the MECHANIC tell me how to make a tool for cutting jacquard card-pins; they are cut in 5in. lengths, about fin. diameter ?-GALA.

telescopes are generally constructed of plano-convex [6735.]—OBJECT LENS.-As terrestrial eyepieces of lenses, the object lens in diverse position to the others, will any of your readers inform me the focus of the obof the latter and distance from the field-lens; the focns ject-lens; its distance from the amplifying lens; the focus of the latter and distance from the eye-lens, and the focus of the eye-lens to constitute an eye-piece of lin. focus, or equivalent to a single eye-lens of that focus? Likewise the rule (not algebraic) for such calculation, and whether it is customary in practice to use a larger focussing-tube for a 4in. object-glass, and consequently increased diameter of the lenses than that used in a 2in., which with me is 1fin. diameter ?-K.

[6736.]-OBJECT-GLASS.-Having a pair of glass discs suitable for a 4in. object-glass for telescope, the focus of which I purpose 66in., would any of your correspondents favour me with the concave curves of the flint disc, and whether they are the same on either side, with the rule (not algebraic) as adopted for this and other foci, and confer a great favour up on a brother subscriber?-K.

occur.

[6797.]-WHAT IS A LINE.-In Dr. Ferguson's "Electricity," p. 103,"133 lines" and "26-6 lines I can understand what a line means in geometry, and I know something of English and foreign measures, also of decimals; but what authors mean by saying that anything should be so many lines thick or wide, I never could clearly understand, although the expression is by no means unfrequent. Will some one have the kindness to enlighten me? Dr. Ferguson is not to be sneered at; his is an important and well-written work.

OLD PLOUGHMAN.

[6738.]-FIGURED GROUND GLASS.-By what method is the pattern upon figured ground glass obtained? My experiments with fluoric acid having failed.-A. O.

[6739.1-BOOT CLEANING MACHINE.-Will any of my brother readers tell me how to make a boot and shoe cleaning machine?-Look Cook.

[6740.]-BLEACHING.-Will any reader inform me of the process of bleaching with either chloride of lime (bleaching powder) or chloride of soda (chlorinated soda), the quantity by weight or strength by Twaddle's hydrometer, that will not injure the article to be

measure, or strength by hydrometer, of acid necessary to liberate the gas; and should there remain an excess of acid how am I to wash it out? Also, would it improve the power of the bleaching agent to saturate without such ?-AN AMATEUR BLEACHER. the article with a soap solution previously, or be better

USEFUL AND SCIENTIFIC NOTES.

ARITHMETICAL CURIOSITY.-A correspondent of the Photographic News says:-"Starting with the hands of a clock at Oh. Om. Os. the minute hand during one hour passes over the several numbers 1, 2, 3.........12; these being added together make the sum of 78, which, being multiplied by 24, the number of hours in the sidereal day, make the number 1,872, or the date of next year. Of course this has never happened before in the Christian era and never can happen again." Here is a coincidence for Zadkiel and

the prophets !

TRANSPOSING PIANO.-A simple invention has been perfected by Messrs. George Carr & Co., of Cannon-street, whereby the transposition has been obtained in a very easy manner. The method is as follows:-The key-frame is made in duplicate, and on it is screwed, by means of ordinary thumb-screws, the At each extreme action, making it perfectly rigid. end of the keys the block of wood, called the "keyblock," is also attached to the key-frame, and thus rendered movable. These blocks are pierced with holes exactly a semi-tone apart, in which small pegs of wood are inserted. When it is required to alter the piano to a higher or lower pitch the pegs are taken out, and the key-board can then be moved with the smallest possible power up or down the scale. To meet the hammers, when used either way, there are extra strings, so as to exable the performer to have a full compass instrument always to play upon, and sufficient length is allowed to make it available for transposition into any key. The advantage of this piano to musicians, especially vocalists, can hardly be over-estimated, as it affords a mechanical means of changing the key in which a piece of music may be set, so as to accommodate the voice of the singer.

CEMENT FOR SEALING EDGES OF THIN GLASS.-Hunt's formula for a cement, which is used for sealing the edges of thin glass, is to evaporate Canada balsam to a solid consistence, dissolve it in an equal bulk of benzole, and then thicken it to about the density of cream with white lead or zinc ground in oil.

THE WIRE TRAMWAY IN THE FOREST OF DEAN. This cheap mode of transferring minerals has been applied for the removal of iron ore from the Devil's Chapel mine to the Severn and Wyre Railway in the Whitecroft Valley. The tramway is 1 miles in length. It is carried at an altitude of some 30ft. The line consists of an endless wire rope, supported by a series of pulleys, which are fixed to and carried over one of the most rugged tracts in the district. The buckets in which the mineral is conveyed carry about cwt. of ore at the rate of 200 an hour. The rope is driven by a portable steam engine. A wooden siding has been made near the Severn and Wye Railway to expedite the delivery.

THE ORGAN IN ST. PAUL'S.-It is proposed to remove the existing choir organ to the entrance to the choir, dividing it into two parts, and placing the one on the north and the other on the south side against the blank wall where the monuments of Lords Nelson and Cornwallis now stand. By continuing the choirstalls to the iron rail, now serving in the place of a screen, it would be possible to erect the organ above the new stalls, and so increase its power, without allowing it to extend more than 6ft. from the wall on either side.

The following are the initials, &c., of letters to hand up to Tuesday morning, February 21, and unacknow ledged elsewhere:

J. K. Laughton, W. Heatherington, Carter Draper, EdHaines, W. D. E., J. & H. Crace, T. N. Turner, R. Cunliffe, J. A. H., John Glenman, A. Brothers, F. H. Chastney, W. M., J. H., Arthur Wm. Waters, Numskull, David Lyon, Jabez Francis, C. Fissett, Ashworth Bros., J. H., Joshua Wood, H. B. Boyds, G. E., J. F., Thos. Simmons, G. J. Hinton, W. A., Jas. Lawton, Geo. S. Chase, Fred. Carre, J. P. McClean, Thos. Andrews, J. H. T., Parisian, Jas. Scarlett, The Harmonious Blacksmith, G. T. R., F. H., Wm. Tonkes, W. Southwood, T. W. C., J. Pickles, Jack of all Trades., Dentes, A Carpenter, Civet, Jas. Burt, J. H. H., Lemas, Carpenter, A Son of Toil, W. S., Australia, Voltaire, Nervous, 8. A. Grimshaw, Box, W. C. P., T. P. Barkas, T. W. Shearing, Delta, T. G., Thos. Holl, A New Subscriber, A. Tucker, X. Y. Z., Frank Chessell, W. Purkiss, A. Z., W. T., H. G. W. B., J. Roberts, A. L., A Mechanic, G. R. Fitt, Musa, A Selftaught Mechanic, Bernardin, Ab Initio, Hy. Habfield, A. P. S., Telegraphicus, Spica, Henry Martell, H. Turner, J. O. Dyffryn, Eos, Thos. Dewson, H. Jones, Cupio Scire, Rufus Wm., A. A. M., An Apprentice, J. R. C., Wm. Long, E. Tydeman, Thos. O'Connor, J. R. C., M. Starr, F. R. C. P., Aroma, W. B. C., Q. Lea, Cornwell, M. T. C., Iriosal, J. Bennett, G. R., A Young Mechanic, Beacon Lough, Hy. Beadling.

The Sixpenny Sale and Exchange Column are the only places in which can appear queries sent by P. R., A Reader, Trafalgar, E. J. S., S. S., Milo, B. E. T. A.,

X. Y. X.

THOMAS CARRUTHERS.-Your letter gives no information. We should be glad to insert a description of your plan. AMATEUR PRINTER.-See Vol. X.

H. PALMER.-See indices to back vols.
ERRATUM. In letter 1858, p. 492, first line, for " analysis"
read analogies.

C. P. E.-See pp. 287, 383, 455, 478, 501, 524, Vol. XI.
J. H.-See articles on "Electricity."
W. H.-He can only patent the process.

J. R. W.-249 can be had, the others are out of print.
YOUNG VULCAN.-See pp. 502, 548, 571, Vol. XI.
E. A. See p. 141, Vol. XI., reply 2577.
FAILURE. It was fully answered in Vol. X.
YOUNG ILFRACOMBE.-Given in Vol. X.

F. G. Buy dollar bills of any money-changer and remit them. Don't forget the difference in the rate of exchange.

No. 170.-It depends very much on our space open. Very few letters appear posted later than the preceding Friday.

W. WRIGHT. See many back nos.

C. J. H.-Write Porter & Lane, 172, Fenchurch-street, Their arrangement for gaslighting would suit you. See back Nos. for electric bells.

W. E.-See back nos. First query answered recently. BISMARCK.-Very probably. The present query can only appear in the Sixpenny Sale Column.

G. O'HANLON.-We have not received it.
THOMAS A. BASS.-Consult indices.

F. W.-Very likely. Please don't send us the method.
J. H. R.-See pp. 310, 834, 356, 502, 526, 547, 548, 520, 595,

and 596, Vol. XI.

A. J. V. GOODEARL.-The last two lines of your letter give the best of reasons for not inserting it. The experiment is simple, and can be easily made by yourself.

HYPERION.-Letter on Telescope, next week.

W. WHITE, of Monmouth, says "My advertisement is left out this week. It is a great loss to me to have it omitted."

J. N. TAYLOR, of Pembroke, says "Your promise of a series of practical papers on music has gladdened my heart."

GEOLOGY IN CONNECTION WITH AGRICULTURE.-"Derf Errac" writes to inform us that the papers contributed by T. Jones on this subject were appropriated without acknowledgment from Prof. J. F. W. Johnson's "Elements of Agricultural Chemistry and Geology." Immediately after the appearance of the last paper from the said T. Jones we had our suspicions and declined further connection with him. Probably we shall have more to say about the authorship of the mposition in a week or two.

CASTOR, who wrote to us first under that twelve months since, is somewhat indic other correspondent should assume the Y. Y.-The article under the beading "Sh nius" was a selected one-in fact, the repor read before the last meeting of the Be tion. We see nothing in it to offend Roma Science and Criticism will inevitali y things unhesitatingly, calmly, and i the followers of all forms of faith will tru them in a similar spirit.

AN INQUIRER.-The space required for the of the merits of Acme skates can be d advantage.

W. S. (Glasgow.)-See back Nos.

AN ADMIRER, ETC.-Much information has lea on printing, which you could have seen subscribed regularly. We frequently do thi all the "suggestions," &c., which reach us o "constant readers" who buy a copy ab twelve months.

THE LIFE BOAT.-Edmund Williams ESE) card or billhead be provided and distributed c those who might feel disposed to collect a for the "Life Boat Fund." Others ha similar suggestion, but we have not wit because some might apply for collecting car giving the least account of the moneys cle DELATEUR.-Please send name and address J. RYAN.-See account of Geological Sociste HY. T. VIVIAN.-Your letter would only pr productive controversy. Mr. Denning is qu of vindicating himself, and it is best be do so. ALGOL.-Write W. R. Birt, Cynthia-villa, Wakan C. HAROLD.-She could consult a physician Toy plication of dyes would probably be hurth-n foolish.

G. HUNT.-Many replies have appearedfind space for. JACK OF ALL TRADES.-Fuller particulars must sketch of sewing machine is to appear. A. Y.-See pp. 600 and 622, Vol. XI. R. H.-Entirely a legal question, only to be answered by a lawyer well versed in such n JOHN TURTLE.-The plan has been many gested, but cannot be adopted. Better have small subscription.

DETECTOR.-We have a wholesome horrerat information. Food adulteration is quite enough.

ONE WHO IS NOT AN AMATEUR.—If you read the
article in our last number, you will see the
perfectly aware of the variation of resistan
and German-silver wire at different temp
you will look at the article to which you re
find that" Sigma "says "the opinions of
differ from mine"; and if you have any
to offer, and express yourself in a gentlema
ner, we will insert it. We are quite cer
your opinions will be treated in & more t
manner than your present effusion treats
"Sigma."

W. GARBETT.-We cannot interfere.
F. H. B.-You cannot be a subscriber,
not have sent your letter to the wrong sh
T. AYERS.-The information was public

and must be imparted for the public good. S. HEWELL says:-" Requiring such articles I recipes of glycerine and litharge, as gr number by Jack of all Trades-solatie d percha in turpentine, and rock-salt and C boiled linseed oil, and found them all

J. L. IANSTONE.-We offer no opinion on thi tised.

W. H. N.-No room for hair-brained notions S. J. REDPATH.-No time to search at the Pa MINNEHAHA. You ask, "Can any of your me full instructions how I can make an orde mometer?" As such a thing can be b shilling, we should say, buy one. We have with questions like this. Last week & Y in two or three lines, wantel "a descrip the processes in the manufacture of e) complete answer would occupy several p

space.

trivial.

R. ANDREWARTHA.-The letter was forwarded to De

not Devon, Cornwall.

A

The English Mechanic

AND

IT

FRIDAY, MARCH 3, 1871.

ORIGINAL ARTICLES.

PHOTOGRAPHY AND THE RECENT
ECLIPSE.

T may probably interest the readers of the ENGLISH MECHANIC to hear something of the photographic operations at Syracuse, and it may not be uninteresting if I say in few words how we got there. The Sicilian portion of the English Eclipse Expedition, under the charge of Mr. Lockyer, started by the mail train from Charingcross on the evening of December 7th last. We arrived at Ostend early on the morning of the following day, and started shortly afterwards for Brussels, on our way to Naples, taking in our ronte Cologne, Munich, Innspruck, the Brenner Pass, Verona, Padua, Bologna, Florence, and Rome, arriving at Naples on the 13th. Much of the discomfort of railway travelling in winter was removed by the good arrangements of the South Eastern and other railway companies, a saloon carriage having been provided for our journey from Ostend to Florence; and, but for an accident to some portion of the ironwork in passing over the sharp curves of the rails in the Brenner Pass, we should have completed the journey to Naples in the same carriage. I may also mention, as a matter of some interest, that the usual inconvenience in passing custom-houses was avoided-in no instance were our packages required to be opened.

Punctually to the time appointed we found the Government steamship Psyche waiting for us in the Bay of Naples, aud on the following morning we were within sight of Sicily. The wreck of the Psyche at Cape Molini, about nine miles from Catania, has been so often described that I shall assume the readers of the ENGLISH MECHANIC know all about it. We were so near the end of our journey that all the luggage and boxes containing telescopes, &c., were on deck ready to be landed. As soon as all the passengers were in safety the instruments were brought ashore, and deposited also on the rocks; and immediately that the boats could be spared they were manned by crews from the ship, and ourselves and luggage were conveyed to Catania, where we arrived in the afternoon of the 15th.

All our arrangements were altered by the unfortunate wreck. Syracuse was to have been the headquarters of the expedition, and detachments were to have been sent to Augusta and other places. Catania became the centre of operations. Syracuse was fixed on as the station for photography, and on Friday, the 16th, Mr. Fryer and I started by rail to Lentini, and thence by road to Syracuse, where we arrived late in the evening of the same day. Dr. Vogel was to have been one of my party, but it was thought desirable to have a second station for an experiment in photography, connected with the polariscope, which Dr. Vogel undertook, and he accompanied Dr. Roscoe to Mount Etna.

It was difficult to realize the fact that less than a week previously we were shivering from the frost of a northern winter; here, in Sicily we were enjoy ing the most agrecable spring-I had almost said summer-temperature. Extra coats and wraps were discarded; and yet it was strange to notice that the Sicilians thought the weather cold, and wore thick clothing. The wind, which we felt refreshingly cool, caused them to draw closer their picturesque cloaks, and to cover their heads with the hoods which appear to be the usual appendages to their cloaks, and very comfortable they no doubt are for cold weather.

shown a tendency to fall. We also observed that Etna, which was about 40 miles distant, and which had been remarkably distinct, became clouded. The morning of the 22nd was somewhat cloudy, but the sky cleared, and the sun remained bright until within about an hour of totality, when a up, and we had almost abandoned all hope of seeing any other eclipse than the one caused by the cloud. Darkness ccntinued to increase, and we saw the sun no more until within a few minutes of the disappearance of the last gleam of sunlight, when the thin crescent of the sun made its appearance through an opening in the cloud, which we could now see was thinning off, and there was a prospect, after all, of our getting some photographs. The sky, in every other part excepting near the horizon, and just in the neighbourhood of the sun, was brilliantly clear.

For about fifteen minutes before totality I had been occupied in the dark room preparing six plates; but when I came into the observatory, about two minutes before the time, I was much struck by the beauty of the sight which at once attracted my attention. The darkness of the eclipse was fast approaching, but there was distinctly seen through the cloud the crescent sun, giving just sufficient light to illuminate the fleecy cloud bordering the denser parts, and producing a very beautiful effect-brilliant rainbow tints being reflected, not in broad masses of colour as we see in a rainbow, but broken up, and producing more of the effect of sunlight reflected from drops of dew than anything else with which I can compare it.

The critical moment was fast approaching. At last, Mr. Fryer, who had been watching through a small telescope for the disappearance of the last ray of sunlight, gave the signal "total," and our work commenced.

I must pause here to say something of the preparation we had made before leaving England, and after our arrival at Syracuse. I will first state what we proposed to do, and then describe how we did it.

Photography was, I believe, first employed by Dr. De la Rue and Father Secchi, in Spain, in the year 1860, when the red prominences were successfully photographed, and at the same time proved to belong to the sun. Again, in India and America the red flames obtained the chief share of attention, but observation had been scarcely at all directed to the corona. Faint traces, however, of this mysterious light were found on the photographic plates. The corona had, indeed, been known as one of the phenomena of all total eclipses of the sun, but very little attention had been paid to it while the prominences attracted so much notice. It was, however, determined by the English observers, that during the recent eclipse, the corona almost exclusively should be observed, and I was requested to take charge of the photographic arrangements. Bearing in mind all that had been done during previous eclipses, it appeared to me that the corona could not be successfully photographed if a telescope were used for the purpose. There are objections to both reflectors and refractors. I therefore determined to attack the matter somewhat differently, and, as the event proved, successfully,

The corona has usually shown itself on the photographic plate merely as a bright light extending a very short distance from the moon's limb; but all observers of the phenomena speak of this bright light as extending much further, and of rays projecting in some cases one or two diameters in every direction around the moon, and presenting all sorts of fantastic shapes. These appearances also have been said by some observers to change during the eclipse. The small extent of the corona hitherto photographed had given rise to the idea that its light was not very actinic, and that a very long exposure would be necessary to photograph the image. That I might obtain negatives showing the rays and a corona such as is usually visible to the naked eye, and also test the matter as to the actinism of the light, I determined to take several pictures, and to give each plate a different exposure.

46°.

in England, and was forwarded by way of Malta (with the other heavy baggage), so as to be ready immediately on our arrival at Syracuse, thus saving time, few hours sufficing to put the erection together. The whole was covered with thin waterproof canvas, and as an additional

protection, chiefly from the wind, a large sail was securely fastened over the building-a protection of the value of which we had ample proof before our work was over.

To the eyepiece end of the telescope (which is mounted on the German plan, and driven by clockwork) was fixed the camera for taking photographs of the partial phases, and also for taking one picture during the totality. Mounted on the telescope was the camera for photographing the corous. I wished to obtain the pictures with short exposures, and yet to get as large an image as possible. Fortunately, an instrument combining these two qualities, a long focus, and quick acting, was available, Mr. Dallmey having very kindly lent me one of his "rapid rectilinear" lenses of 4in. aperture and 30in. focus, giving an image of the sun 3-10in. in diameter. This lens was fixed to a camera adapted for plates 5in. square. Six dark slides were prepared and fitted for use in either camera. As I had to do the whole of the photographic manipulation myself, a large number of partial phasepictures could not be taken-time was lost in the preparation and development of the plates—but I secured about nine negatives before clouds prevented further work. My plan was to prepare three plates, and expose them after intervals of two minutes; then develop, and so on, up to the time when it was necessary to get ready for the totality.

I had found that it required two minutes to prepare each plate; and at fifteen minutes before totality, I commenced the preparation of the six plates required. No. 1 was placed ready in the camera for the corona, and No. 6 was put into the telescope camera ready for exposure at the proper time. We had arranged a scale of exposures varying from three to thirty seconds; and we had found, by repeated drilling, that it required about six seconds to change the slides and make the exposures. We had previously decided that we would go through the ceremony of exposing the plates, regardless of the atmospheric conditions at the time, and so take the chance of any break in the cloud which might occur. Exposure No. 1 was, therefore, made with very little prospect of success, and it came out blank, No. 2. and the others following in their proper order; the whole showing results, but No. 5 giving a perfect picture. The cloud had completely cleared away by the time this picture was taken. No. 6 was exposed three seconds in the telescope for the prominences.

The plate No. 5 was exposed eight seconds. It is, of course, impossible to say whether this plateshows as much of the corona as would have been seen on the plate exposed thirty seconds if there had been no cloud at the time when that picture was taken; but, as it shows the corona extending about a degree on the north and west sides of the moon, and less on the east and south, and as one of the observers who was watching through a telescope for the reappearance of the sun assures me that there was no cloud at the time my photograph was taken, it is, I think, safe to assume that the whole of the corona is shown on this plate.

How could six photographs be taken in 105 seconds? This is a question which will no doubt occur to many readers. It was done in the manner following:-Mr. Fryer stood at the end of the telescope ready to uncover the camera at the appointed time. Lieutenant Spaight (who had very kindly consented to assist us) was standing near my right hand ready to give me the dark slides, and to take those already exposed from me, and Sapper W. Gardiner was at the chronometer counting seconds, and I was stationed at the telescope. The changing of the slides was effected in six seconds each, and at the finish we had about two or three seconds to spare.

It may be asked why we did not use repeating frames. This was thought of, but decided against, for reasons which I need not particularize here.. I believe the plan adopted was the best.

Immediately after the end of totality I commenced the development of the plates, and most anxiously did I watch for the appearance of the image. My anxiety was not of long duration; the picture was there, and good beyond all expectation; this was plate 5. The other plates were all under-exposed, as I have before stated, owing to the partial cloud.

Early in the day a strong breeze sprung up, and at the time of the eclipse it was blowing half a gale; consequently clouds of dust covered everything. This we attempted to keep down by watering, but only with partial success; and worse than all, the cloud, no larger than could