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their milking scratches on the thicker parts of Bome small shafts that I was turning. I could, however, have followed up these scratches with the screw tool and have produced the wonder of a triple thread from single dies.—J. K. P.

[4434.]—TAPS AND DEES.—W. Reed can make lefthanded taps and dies very easily: he has onlvto work them the other way or backwards.—SsatPsu Paratch.

[4489.]— MATHER & PLATT'S PATENT PISTON.

«* c. S. A." should write to Mather & Piatt for the

spring clip (I presume it is Barker's patent), and they will send him one, no doubt, and also the necessary information with it. Tho address of Mather & Piatt, engineers, is Salford, Lancashire—Wahsrof.

[4441.]— BAROMETER.—I must ask "Junius" to eatamine the index closely, and he will find that the degrees of temperature increase in u direction opposite to the tube graduations on circle rf d d, so that as the temperature rises the liquid falls and tho ratio in lay l?lass is -4in. for 1- Fahr. more or less, thus : e.g.

543 Fahr. = 6 inches \

££ " = £*S" I Barometer steadv nt 30-5

62° „ = 28 „ ) This must be found by experiment for each glass, and it, is only necessary to select a day when pressure is Mteadj/. Having inscribed your circle d d rf as directed, place a blank circular card therein, and mark on the xxiargin the teraporaturo at that time. This figure must of course coincide with the liquid level on d rf d. An hour After the temperature will havo probably altered 1° Fahr. more or less. Set down this new number opposite its reading on rf d d. A certain interval of tentha will bo

the same fluid. Or chloride of zinc, 10 grains; distilled water, loz. I fancy you will find one of the above solutions to answer. I have never mounted rotifers, but have used them successfully for a great number of animal tissues, and dissections of insects. The vulcanite rings answer extremely well; in fact, they are the most useful cell made.—Operator.

[4449.]— RESTORING FRESHNESS TO FILTERED WATER.—The flatness of tho filtered water, and of that which has been boiled, proceeds from the same causeviz., the absence of air. If, therefore, "F. P. S." will aerate his water after filtering by pouring it from a watering can with a fine rose held at a height of about 3ft. or 4ft. (if necessary repeating the process) he will find it as fresh and palatable as before. The same effect will be produced on boiled water.—Vertumnus.

[4449.]—FRESHNESS TO WATER.—Pour sharply from one vessel to another; or, better, pass carbonic acid gas (easily made from chalk and sulphuric acid) through it.—H. P.

[4451.] —MOULDS OF COINS.—Fusible metal mak es very fine moulds of coins, and avoids the trouble of blackleading. Gutta-percha softened in hot water also answers well if it is placed on the coin, and the two put on a piece of plate glass in a prets. An ordinary copying press will answer well. Sulphur and whito wax are also used; and for small coins, ordinary scaling wax will answer for a rough experiment.—Operator.

[4451.]—MOULDS OF COINS.—They can be made of gutta-percha, or wax, or plaster of Paris. I recommend wax, which I should uso as follows:—Greaso the coin and fix a cardboard ring round tho coin, and then pour in the wax, melted; when it has set, take it off and re

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found for 1'; with a compass mark off the rest around the card. Supposing the interval = 5in., then there will be 2° Fahr. for each inch rise or fall. Any work on "Pneumatics" explains the law of expansion of air, &c, but such a calculation would be difficult and probably inaccurate compared to the plan suggested. In case of barometer falling I can only repeat what appears with illustration (53) : with, however, a correction in 6th line from bottom, the words "pointer a " should be "54-on card." As the position of pointer is confusing where now placed it will be better to fix it In the blank space between 50* and 66-. A larger index is forwarded as desired, but I fear space is too valuable forits insertion. If "Junius " fails now I will draw out an index for him.

—CORNPDIA.

[4442.]—CROQUET.—"Woodman" can buy a book of croquet instructions at almost any bookseller's for 6d., which will give him all the information he asks for. lie will find crabtree or maple as good as anything for his mallet heads and balls, and quartered ash for mallet handles and starting posts.—Wood Spoon.

[4445.]—ASPHALTE FOR GARDEN PATHS.—I had some done by my own man, and if " Sabbas" will get it from the gasworks prepared he can easily lay it down. Mixing the what is called asphalte—i.e.,' the crushed cinders saturated, or nearly so, with tho gas tar, with old lime, broken bricks, bits of limestone rock, Derbyshire spar, &c, to taste, and thou well rollered several times.—Wahsrof.

[4446.]—MOUNTING MICROSCOPIC OBJECTS.— I don't think "H. U." will derive much advantage from mounting rotifers, as any medium in which they are mounted will cause so great an alteration in them as to render them useless; besides which, these creatures have an awkward hlbit of going to smash. Their natural end seems to be diffusion. If, however, " H. U." wishes to irJf $£5J^P0riment of mounting them, he had bettor use ThwjrtfTs liquid, or glycerine and camphor water. Pumphrey's vulcanite cells aro so cheap (Is. per 100) that no excuse exists for trying rubbering*. The latter are a plague to use, but will answer their purpose, when used, most admirably.—H. P.

[4446.]—MOUNTING MICROSCOPIC OBJECTS.— I fear it will be difficult to mouut a rotifer so as to keep well, without causing a great alteration in its appeal nee. Try one in Bean's medium, but mounted in a cell, will be most likely to succeed. Try by soaking the rotifers in water saturated with creosote, and mount in

peat the process on the other side; next stick them back to buck, and brush it well with plumbago (a fine quality black lead), it is then ready for electrotyping.—Semper Paratcjs.

[4451.] —MOULDS OF COINS. —White wax, with

flake white added, gives very good impressions of coins, &c.t which should have a narrow slip of paper gummed round their edges, to hold the wax when poured in a melted state on them. These should, when cold, be coated with plumbago, applied in powder by a camel's hair pencil till the whole surface of the wax assumes a polished appearance.—J. B.

[4151. |-MOULDS OF COINS.—I take impressions on moulds of coins in this way. I use them for medallion cutting by Lowe's machine (the cheapest, neatest, quickest, and best out):—I first get some gutta-percha uf a thickness to suit the coin or medal to be copied and steep it in warm water until it becomes soft, and then warm the medal and lay it on the gutta-percha, and simply place a 141b. weight upon it. This does one side only—the same is required for tho other. I then rub tho gutta-percha impression with the finest plumbago (prepared for electrotyping) and submit it to the sulphate of copper bath/ using the finest sulphate of copper and the carbon battery, and have got some very good impressions.—Wahsrof.

[4451.]—MOULDS OF COINS.—If it be required to produce mould* of coins so as to obtain facsimiles in electrotype copper, the best plan is to make impressions in scaling wax on note paper, then,| to avoid warping, attach them to a heated copper wire, and then thoroughly blncklead the surface. I have a considerable collection of Grecian, Roman, and English coins made in this way when electrotyping was in its infancy. The mould of each side was taken closo together on tho same piece of paper, and a smooth connection between them made with soft white wax, enabling them to be trimmed up so as to show the obverse and reverse side by side, attached by a band, as shown in engravings. They may be sihered or gilt to represent the original; "when larger than a florin gutta-percha will be found to be the best material, as both this and sealing wax have the merit <>f not injuring the surface, which can hardly bo said for stearine and spermacetti, 4c—W. K. B.

[4452,]—LIGHTNING CONDUCTORS.—Rod iron is generally used for them. A good size is gin. Thev should reach above the highest part of the building, and be pointed at tho top. The points of contact with the

supports on the side of the house, are preferably of glass; but that precaution is mostly ignored, and the rod must be inserted in the earth to the depth of about a foot or so.—Semper Paratus.

[44531— BACKGROUNDS. — I do not recommend backgrounds to be rolled up. If the stretcher be made wiih wedges, like the stretchers used for painters' canvas, a tap with a hammer now and then will keep it tight. To paint a background, use a coat of size and whiting, with a little glycerine for first coat; and after that is dry, lead-coloured paint, containing a large proportion of turps, will give a perfect dead surface without gloss that will not crack if used with care.—OpeRator.

[4457.]—STEAM BOILER.—It often happens a bleaching and printing works that, though they use the steam for boiling, Ac, after the great pressure has been taken out of it by the engine, they require more steam at a reduced pressure to that in the boiler—and there are many makers. But Messrs. Musgrave <fc Son, or Messrs. Hick, Hargreaves, & Co., of Bolton, make what are considered very capital reducing valves.—

WAHaROF.

[4458.]—BLACKING FOR HARNESS.—The following recipe is given by good authority :—Treacle, Jib. J lampblack, loz.; yeast, a spoonful; sugar eandy, olive ou, gum tragacauth, and isinglass, each loz.; and a cow's gall. Mix with two pints of stale beer, and let it stand before the fire for an hour.—G. H.

[4459.] — FURNITURE CREAM. —The following is said to be good:—1st, Soft water, a gallon; soap, 4oz.; white wax in shavings lib. Boil together, and add 2oz. of pearlash. To bo diluted with water, laid ou with a paint brush, and polished off with a hard brush or cloth. Or, 2nd. Wax, 3oz.; pearlash, 2oz.; water, 6oz. Heat together, and add 4oz. of boiled oil and 5oz. of spirits of turpentine.—G. H.

[4459.]—WHITE FURNITURE CREAM.—Take of raw linseed oil tioz.; white wine vinegar, 3oz.; methylated spirit, Sox,; butter of antimony, £oz.; mix the Unseed oil, with the vinegar by degrees, and shake well so as to prevent separation; add the spirit and antimony, and mix thoroughly.—R. 8. Neilson.

£u61.j — SCREW CUTTING. —In answer to "H. WiRiams," I should use wheels of 12 gauge, provided they can go on to tho mandrel, in which C»bo the distance between the centre of mandrel and centre of loading screw would be about 7in. If his lathe has only one collar, and a cono centre bearing behind, he will have to put a wheel on the back of his pulley working into another wheel supported by a bracket, and to put the driving wheel of his train into the spindle of this second wheel. In this case the distance of centres would probably (it need not) be much less than 7in., and teen wheels as small as 20 gauge are handy. Mine are of 20 gauge, but are gun-metal, cut wheels. Also in this case I should make the mandrel wheel double that carried by the bracket, and use a left-handed leading screw of 8 to an inch, which would by this arrangement be equivalent to a right-handed screw of 4 to an inch applied in the ordinary way, and that is the pitch of scrow that I am now putting to my old fan. lathe in place of one of 10 to an inch that I find too slow for what I now roquire, only my new screw is of double thread, cut with a screw tool of $ pitch. ;l have nearly done my new double-geared Sin. head stock, and shall show it with pleasure to any one who wishes to see it and will first addroas a letter to me per the Editor English Mechanic.—J. K. P.

[4462.]—STRANGE PHENOMENON.—The phenomenon described proves that " Glowworm" is one of thoso few persons that are capable of being affected by, or sensitive to, odie force. I should feel obliged if " Glowworm," if he has a chance, would experiment a little on tho subject, as the existence of the odic force is denied by many. The following is an experiment I recommend him to try: Get a magnet as powerful as possible, and first request a friend to pass it down his back with the poles or ends nearly but not quite touching the dress, commencing at the back of the head and slowly drawing it downwards towards the feet, and carefully note the sensation it produces. Afterwards take the same magnet into a dark room at nighty so as to exclude every trace of light, and placing himself about a foot from tho magnet look at it attentively for some timesay half an hour—and also note the phenomena that take place. I shall feel obliged by these simple experiments of iiig tried by " Glowworm," as they will help to confirm the truth of a little known and despised branch of science. If successful I will describe other experiments to be tried. The light observed by"Glowworm" is caused by the chemical action taking place in tho loaves. I can, if required, uamo manv places where tho above light will bo seen; over a new-made grave it is very often seen, and no doubt has frightened sensitive people terribly, while another person not sensitive would not tic able to see anything unusual. In fact, in every case where chemical action is taking place the light will be seen to a greater or less extent.—Operator.

[4464.] — THE MANGANESE BATTERY.-In reply to "M. D.," I beg to state that I am still a regular reader of tho English Mechanic, and, by your courtesy, an occasional contributor to tho correspondence. The manganese battery continues to work perfectlvwell, and hardly diminishes in strength. It has been absolutely untouched for many months, with tho exception of an occasional addition of water to replace evaporation; The clock keeps better time than a good pocket chronometer in my possession—W. H. Stone.

[4465 J -TRACING PAPER.—This may ho prepared by brushing over one side of a good, thin, unsized paper \wlh a varnish made of equal parts of Canada balsam and turpentine. If required to take water colour, it must be washed over with ox-gall and dried before being used.—T. W. Boord.

[4465.]-TRACING PAPER.-" H. U." can make a

good tracing paper by mixing, with the aid of gentle heat, an ounce of Canada balsam and aquarterof a pint of spirits of turpentine. Wash one side of tho paper witli this mixture. The black oarbonic papers are made by being "painted" with a composition consisting of 2oz. of tallow, \oz. powdered blacklead, $ pint of linseed oil, and sufficient Lunpblaek to make it of tho consistency of cream. These should be melted together and rubbed on the paper whilst hot. Wheu perfectly dry they will be fit for use.—C. T. R.

I

[4466.] — CLEANING PRINTS.—Immene tho print in ft bath made by adding to strong muriatic acid Its own weight in water, and to three parts of this mixture putting one ol rod oxide of manganese. A print may remain in this liquid 34 hours without harm. If the print has been mounted the paste or other adhesive should be entirely removed previously with warm water. The saline crystals left by the solution will wash away by repeated rinsings with warm water.—Sabbab.

[4487.]— IMPRESSIONS FROM PRINTS.—I give the following recipe, but I have not proved it:—Soak tho

?Tlnt in a solution of potash, and afterwards in one of artaric acid. This produces a diffusion of crystals of bitartrate of potash through the-unprinted part of the paper. As this salt repels oil the ink roller can be passed over the surface without transferring any of its contents to the paper, excopt in those parts to which the ink had been originally applied. Tho ink of the print prevents the penetration of tho saline matter, and so only the lines of the picture will take the ink from tho roller.—C. T. R.

[4474.]— HORSE POWER.—" Lloyd's Sliding Rule" will show the horse power of any high-prepare engine, the pressure on the safety-valve of boiler and diameter of cylinder being given.—T. W. Boobd.

T4478.7 —BLUE WRITING INK OR FLUID.—One of the best and simplest is made by dissolving soluble Prussian bkie in distilled water. The blue is obtained by adding a solution of proto-sulphatc of iron to a solution of ferroyanide of potassium and washing the precipitate, fitter it has acquired a deep blue colour, until it begins to dissolve in the water; it may then be either collectod and dried, or at once dissolved for use.—T. W. Boord

[4479.]—COLLODION.—In order to avoid ridges when coating tho plate, it should bo rocked to and fro while the superfluous collodion is draining nff into the bottle. I should think that W. Crawley's collodion is too thiok.—T.W. Booed.

[4-181.]—BAROMETER SCREW.—There seems no difficulty in determining whether the screw was in any case meant for the use Mr. Tomlinson mentions, by merely measuring whether the scaleis divided into true inches or diminished ones. They ought plainly to be always less than fall inches in the ratio that the lower mercury surface is less than both surfaces together. Rarely is the tube so small relatively to the cistern that a variation in tlw difference of level would practically be all visible at the scale. If its inches then are not diminished, I should conclude the original designers contemplated this very clumsy adjustment of level at every reading.—E. L. G.*

[4482.]—OVAL.—The following method of describing fiU "egg-shaped oval" is taken from "Burchett's Practical Geometry "—a ufficicnt answer to the second part of John Barton's query:—Upon any right line AB

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describe a semicircle CD, equal in diameter to the proposed oval. From C and D, with the radius of the *emioircle, cut the right line in A and B. From A and B, with radius EC, describe arcs CE and DF. Prom A or B draw a right line through tho transverse diameter, cutting it in G, to'iehingthe opposite arc in EorF. From G, with radius GE, deseribo arc EF, completing the iigure. Note.—Tho length of the figure may be increased or diminished by increasing or diminishing the radii AD and BC, and by placing the point G higher or lower on the transverse diameter.—J. Nash.

[4482.]—OVAL.—Works of high geometry, as Sir Isaac Newton's "Euumeratio Linearum Tertii Ordinis," describe plenty of geometrical curves more or less eggshaped—as that described by a point in tho connecting rod. Fig. 1, p. 4-18 (July 29), bnt all such ovals, being of equations above tlie second order, are beyond treatment in popular books. If the question be one of mere drawing, tho outline of a hen's egg is best represented, Mr. Dciiisoti says, in his "Astronomy without Mathematics," by a seini-ellipse for the small end, joined to a semicircle for the large. Many more elegant ones, »s the plover's, are rather composed, I think, of a parabola with a circular arc, which in that case must always be more than tho semicircle. The more you have of one . curve the less of the other,and the more of parabola the longer the egg, and the greater the circular radius relatively to the parameter. An inferior but passable imitation may be composed of six arcs of circles, but hardly of four; though the drawing books affect to form thus an ideal egg-shaped human head. It should also be known tint no ellipse, visibly or plainly different from a circle, can be decently imitated bv fewer than eight circular arcs. The arches of old" lilackfriars Bridge might have only four, but few probnhlv noticed that they were oval at all. The Roman amphitheatres were, as may be seen by all foreign plans of them, all struck from eight centres at least—never from four—as engraved in one of Mr. Fergusson's books, or like the Kensington H«iU of Science. In fact, no race that has anywhere lett monuments, before the English of this reign, over tolerated anything like the crippled fourcentred ovals of our builders. Tho Victorian loss of ** eye," or sudden barbarizing, in one generation of all taBte in form or colour among us, is a really new and world-wide nuisance, one that, though accounted for, will make tho Hgo stink to all others while a relic of it lasts.—E. L. G.

[44*7.J —BURNT CLAY.—The red colour is due to the decomposition of salts of iron during the process of burning,—T. W. Booed.

[44S9.J—TURNING COPPER.—Reduce the width of tho cutting edge of tho tool.—T. W. Kookd.

[4493.]—COIL.—For my own experimental, use I designed and uiado ft commutator, such as " R. N." de-ires, bat it is a troublesome job and requires diagrams to explain. It consists of an ebonite cylinder with three scries of contact arrangements; the middle one for the primary, the two sides corresponding one to the

contacts and the other to the breaks of the primary. There are springs and the requisite conductors to direct the course of the current. I may hereafter fully describe this and its works, but it would be useless for " R. N.'s" purpose, because the driving out of the tube affects the intensity only, not the quantity, and therefore makes no change in the chemical or galvanometric results. I do not at the moment see how to assist " R. N. " in gaining his object The tangent galvanometer will be fully described in my nest paper. The British unit is about one twenty-fifth of Yarley's.—Sigma.

[4404.]—DISSOLVING RESIN.—You need not dissolve the resin; add to the flour with which you intend to make your paste 1-6 to \ of its weight of very finely powdered resin and proceed as usual; this with tho addition, when mado of a minute quantity of creosote, oil of cloves, or corrosive sublimate, will keep a long time. —T. W. Boobd.

[4500.] — SILVER THIMBLES.—Those and other silver articles, when tarnished, may be cleaned by washing with caustic ammonia.—T. W. Boord.

[4608.]—MENSURATION OF SUPERFICIES.—The area of " T. W. IL'a " triangle is *J0*tfltf7, aud the following is the manner of working it:—

9-a + 7-5 + 5*5

2" -111

11-1 -9-3 = 1-9
111 - 75 = 86
11-1 ~ 5-5 = 5-6
11*1 xHx 3-6 x 5-6 = 4351724
4'25-1724(20-6197
4

406\O2517
6 ' 2436

4121 \ 8124
1/ 4121

QUERIES.

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J. Nash,

[4506.1—WATER BAROMETER.—I should be glad to help " tiimel " without price, hat glass in perishable, and a journey would be fatal to such a fragile arrangement; { besides, each glass requires at first a careful oeries of < observations in order *o construct its index (see reply J to "Junius" in this number). Any handy workman would easily construct the glass from the drawing, and if " Gimel " could ^paro ten minutes a day for a week, he would get thojraufc'', and could form index therefrom.—

COKNUBIA.

[4507.] — MUSHROOM CULTURE. — W. Reed can scarcely expect to grow mushrooms in nothing but mould. The delicate filaments which form the roots of this fungi could not possibly spread through a mass of loam. If he will put about three-fourths dung to onefourth mould, and well mix, I have no doubt he will succeed. Possibly a lets quantity of dung would do if the mould used i'* lull of fibre—like turfs cut from an old meadow. But will not tho temperature on the top of the boiler be rather too high ?—Saul Rvmea.

[4509.]— BRASS TUBES.—Brass may be polished with crocus and oil alter properly smoothing with emery, but should then be lacquered to* make it retain its brilliant surface. Both soldering and brazing have been often described.—T. W. Uoohd.

[4511].—WEIGHT OF BALL.—To obtain the weight of a cast-ironfall multiply the cube of diameter in inches by-136. For wrought iron multiply by-146, which will give the weight in lbs. To find how much wire ^in. round can be made from a ball 7in. diameter, first find the weight of a yard of the who by multiplying the square of diameter by 7'854, which gives tho weight per yard in lb. Then divide the weight «.'t ball by the weight per yard of wire. The result will be the number of yards of wire, exclusive of waste in process. By the above rule "Kalpli Williams" will find the weight of a wronghtiron ball, 7in. diameter, tu bo 501b., and tho weight of a yard of Jin. round wire about half a pound. Therefore

— = 100 yards.—Ferrd*. 5*

[4511.]—WEIGHT OF BALL.—I think "Lloyd's Improved Sliding Rule" would nuit Ralph Williams, price about 4s, On referring thereto, it appears to me that a cast iron ball 7iu. in diameter should weigh 471b.,and one of wruught iron 50lb.—T. W. Boord.

[4511.]—WEIGHT OF BALL.—An iron ball 7in.

diameter would weij.'h 49'65'21b.; for the weight o^f a cubic foot of cast iron is 7645oz. A\oir. (Hntton), and the cubic content of a ball Tin. diameter is 17y"5i*4S cubic inches. The following formula will show the working:—

"3 y -5236 x 7645

m^TTo "4fl'652 +

A simpler rule, tl oughuot so exact, is: 9 times the cube of tho diameter, Unidol by 64, will give the weight in pounds. So,

7* x 9

—£j- = 43-334375

The rule is found by assuming that the diameter of an iron ball weighing 91b. is 4in. It is not quite so much; hence the inaccuracy. This may be drawn into 804 8 llths feet of round wire iin. diameter. The solidity of lit. of this wire is found by multiplying the square of the diameter by "7854 and then by 12. This product, divided into the solid contents of the ball, will give the number of feet into which it can be drawn.

1795948 804-8 or m Mil*.

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[4582.]— TELESCOPIC, Etc.—Will one of the many readers of your publication iuform ine whether it would be considered good work for an Sin. reflecting telescope to allow Jupiter's second and third satellites nfty-eignt minutes after sunriso, the sky being entirely free from cloud?—H. A. C.

[4533.]-FURNACE FOR HEATING MOTJLDS.-I understand there is in use in the forges in Staffordshire a patent furnace for heating the moulds from which ppades and shovels, &c, are manufactured. The furnace H small, of an oblong construction, and lias apertures on nofa side sufficiently large to admit one or two moulds. Tbo oud directly opposite the blast is left open, and acts as vent hole and feeder, into or through which the fuel is pushed. Can any rcadov furnish me with particulars of tiie construction of this furnace, or give me i ny idea who is the patentee—i.e., if the thing is really patented? —Wi Scott.

[4534,]—SPECULA GRINDING.—TO MR. PURKISS.—Will Mr. Purkiss be good enough to say whether his machine for specula grinding (desribed in the English Mechanic) would do for tha grinding, polishing, and parabolizing of planoconvex len-es of 4in. oroin. in diameter? If large lenses (pliiuo-convex) could be parabolized by his machine, could not a large aud cheap object-gla98 be constructed with facility? I presume that a couple of largo lenses both plano-convex, one flint, and the other crown glass, lckrabolized, would be a euro for spherical and chromatic aberration? Could the lenses be tested in tho same manner as his specula?—Raymond.

[4335.]—HORTICULTURAL.—Can any one give me a lew instructions concerning pruning gooseberry and currant bushes ?—G. H.

- [4536.]—MELTING POINT.—What melting point should I get when I mix paraflines having melting points of 128- and 109 in the proportions of a to 1, 3 to 1, and4 to 1 respectively? Correct answers andhow it is done will oblige. Is there a latent heat to be taken into account V—Melting Point.

[4537.1—EQUIVALENTS.—Would Mr. G. E. Davis or any of your chemical subscribers kindly favour me with tt lint of the elomontary substances with their equivalents, according to the new notation ?—MaO Co'.

[4583.]—HARMONIUM PAN.—I have an harmonium And I have spoiled the pan experimenting with it. Can Mr. Smith or "Adept" oblige me with the depth of channels, pallet, and reed-holes for a two-row pan, as I should like to make one (or try to do so)? If thoy would oblige I should be thankful.—W. A. S.

[4539.]—CHIMNEY.—Tho firm whose engines, shafting, and machinery are under my charge are about to build a new chimney, and I shall bo much obliged if you or any of your correspondents will give me the best proportions for it, especially aj regards height and size ol flue . There are fouv Galloway boilers to be attached to tho chimney, each 24ft, by 7ft. diameter, with 24 Galloway tubes in each; there is al3o an economizer between tho boilers and the foot of the proposed chimney. The works are situated in a valley with hills all uround. —William Moody.

[4540.] — MOUNTING PLANE MIRROR IN REFLECTING TELESCOPE—I should feel obliged if Mr. Proctor or other of your numerous contributors would inform me if there arc any drawbacks to a system of mounting the prism or plane mirror in reflecting telescopes shown in the enclosed sketch. The speculum

U slightly inclined, as in Herschell's, and the image is received on a reflecting prism placed at tho side, the prism being a portion of the oye-pioce. This form would seem to me to possess the advantages of an increase of light combined with simplicity of construction, but having had no experience in such matters, I should liko to know the opinion of some one of your able writers.—A. White

[4541.1-EMBROIDERING MACHINE.—Can any of your readers tell me upon what kind of a machine the embroidered ia = .nion for ladies' white petticoats is executed? Th_- sewing material is woollen, and the stitch a cha i somewhat similar to the Willcox and Gibbs' stitch. I have tried to embroider on the Willcox and Gibbs, but I And it very difficult to make n sharp curve, owing to the great length of the feed. Is there any other chain-stitch machine better adapted lor the purpose? I fancy there is. A reply would greatly oblige.—A. Rraidbk

[4542.]—STEAM PUNCHING PRESS.—Will any of

your readers show mo how to set steam power to work a vertical screw press, t.«., a press of the kind used for cutting out steel pons by hand, bat on a much larger scale? I want 50 blows per minuto. An excentrie motiou, as in toe common punching machines, will not do. Toothed wheels will not do. The motion must be continuous, as the work is too heavy ami has to be too quickly done to allow of a reversing action.—Punch.

[4543]— TORTOISE-SHELL COMBS. — Could any reader tell me how to join tortoise-shell combs ?—Haiu

imESSER.

[4544.]—PHOTOGRAPHIC. —Can a photographer ffive or sell cartea-de-visite of persons ho takes to other people without their consent ?—Photo.

[4545.]— HOGG'S SECRET CODE.—Will "Cryptographer" please give me the information for finding a clue to the cipher, as he promised in No. 273, and also any suggestion he may have to mako respecting secret codea ?—Abqub.

[4546.]— DIVISION PLATE, fta—Will "J. K. P." kindly give the be*t numbers for a division plate having three rings of holes, and say whether he considers it impossible (or nearly so) for an amateur to fit np a back-geared headstock haviug two steel cones running in steel conical collars (both to be hardened and ground to a At)? I also want to know the best anglo for the cones; 35- appears to me too great ?—Bikrlala.

14547.]—A FIELD OF BARLEY GROWN FROM OATS.—Can any correspondent throw any light on the following, which I extract from Elihu Bun-it's " Walk from London to John o' Groats "?—" It waB a large field of barley grown from oats. The barley sown in this held was tho first-born offspring of oats. The head and berry were barley, and the stalk and sheaves were oats : and the whole proeess by which this wonderful transformation is wrought is simply this and nothing more:—The oats arc sown about the last week in June, and before coming into ear they arc cut down within l^in. of the ground. This operation is repeated a second time. They are then allowed to stand through the winter, and the following season the produce is barley. Tbjfl is the plain statement of the case in the very words of the originator of this process, and of this strange transmutation. The only practical result of it which he claims is this, that the straw ot the barley thus produced is stouter and stands more erect, and therefore less liable to be beaten down by heavy winds or rain. Then perhaps it may be added this oat-straw headed with barley is more valuable as fodder for live stock than the natural barley straw. But the value of this result is nothing compared with the issue of the experiment as proving the existence of a principle or law hitherto undiscovered, which may be applied to all kinds of plants for the use of man and beasts. If any reader of these notes is disposed to inquire more fully into this subject, I am sure he may apply without hesitation to Mr. John Elkins, of Bruntisliam, near St. Ives, Huntingdonshire, who will supply any additional information needed."—S. G.

[4546.] —IMMERSION LENSES.—What are the principle advantages of the immersion objectives? Do they cost much ?—M. J. 0.

[4549.] —DOES BOILING DESTROY GERMS.—I should like to hear the opinion of your numerous microscopical readers on this interesting question. According to some authorities, there are some germs which are not destroyed unless tho temperature of the water is raised 10J or 12- above boiling point.—Sabbas.

[4550.] — THE SMEE AND BICHROMATE BATTERIES.—I am disappointed with a Siguia's" answer to my query (4450), and after procuring the numbers he this week recommends, find myself very little wiser. At pago 841, " Sigma " describes the double cell bichromate battery, and says, "Its use in a simple cell system will bo referred to afterwards," which has not been the case for this week at pago 482, he says, "Bat I have now dealt with all tho forms I can remember of any general interest aud practical value, and therefore conclude this part of the subject." "Sigiua's" descriptions are not clear enough for the ordinary mind. For instance, the sulphate of lead battery, described at page 482, would puzzle 99 out of every 10O to tell what it was like, and I am sure, from the description, no one could make one. Will auv other of your readers auswer my query, No. 4450 V— M.R,C.S. (a New Subscriber.)

[4351.] — TRANSFERRING ENGRAVING8 TO WOOD. —Can any fellow-reader tell me a simple way to transfer engravings from paper on to wood, and oblige.—Wood Spoon.

[4552.]—AVIARY*.—Will any one tell me what birds I can keep together in an aviary ?—Rebaf.

[4553.]—SILVERING CLOCK DIALS.—Would "A Morayshire Man," or some other corre-pondent, tell me why I, as **ell as "Poor Clock Jobber," cannot silver a brass plato properly. I had an old-fashioned barometer brought in last week to have the dial silvered. It is one of those which has the mercury shoVing all up the centre. So I accordingly set to work and carried out " A Morayshire Man's" directions to the letter, and, I must say, succeeded in putting the silver on very well; but, on account of applying a dirty brush to varnish it, I spoilt it; so I set to work and scoured oil all the old silver, and began afresh—but all to no purpose; for after 1 had been rubbing tho silver on a little bit it looked just like a decayed bit of bone. I then tried again; and all round the" plate near the edges it looked more like copper than anything else; and as for the edges of the plate thoy looked quite black. How is the plate fixed whilst silvering? I lay mine on a clean bit of rag ?—Young Country Watchmaker.

[4554.]—THE PENDULUM.—Tho law of pendulum motion is, that a weight suspended by a silken cord will move in unequal spaces in equal times. Why, then, should a clock gain time by raising the bob, as by tho law a longer swing should be accomplished in the same time as a short one ?—Vibrator.

[455D.J—PHOTOGRAPHY.—Will some of our readers kindly give tho best process for enlargements upon paper; also the best mode of preparing albumenized paper, and how to free a bath from acetic acid? What is the autotype printing process ?—Lex,

[4556.] —TELEGRAPHY.—May I ask some one the use of A in the diagram? It is affixed to the telegraph

is 82ft. Gin. long, 6ft. 6in. diameter, two tubos running through it, each lift, diameter.—Tnoy. Davlks.

[4560.]—PAINTING CISTERN.—I have an iron soft water cistern. Can any one tell me what is the best thing I can use to paint the inside with? It has been painted with good white lead point, but it has shelled off and the white lead fallen to the bottom of the water.— Cistern.

[4561.]—ENGRAVED BRASS PLATES.—What is the. general modo of filling in engraved brass plates?—T. D.

[4562.]—VIOLIN STRINGS.—I have a number of violin first strings which I keep in a tin box. Will some reader kindly inform me if I ought to take any otherpreeautious for preserving them besides that of keeping them from the air ?—R. E. G.

[4563.]—COPPER AND BRASS COINS —I should bo much obliged if any of the readers ol your valuable paper

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poles. I heard it suggested that it was intruded to hold the wire in the event of the porcelain head breaking. Howover, they are always put on the inside of the pole if they have any strain.—Mus.

[4557.]—WOOD ENGRAVING.—I havo cnt out a

largo stoamer for a billhead, but had the sea too coarse and (men. Could auy one inform me of a composition (if there is such a thing) with which I can till up the hollows, and re-engrave, or mast I have the piece cut off and reversed, and engrave again?—Mus.

[4558.]—STEEL PLATES.—Could any one inform me of the price of eteel and copper plates for engraving upon.—Mus?

[4559.]— HORSE POWER.—Please inform me the horse power 0f &J boiler; it is working at 40lb. per inch. It

send sketches if you can afford space for their insertion ?— Giles.

[4565.] — INDUCTORIUM\S COLL. —Will "Inductorium" kindly state where the ebonite tube may be obtained? also the probable cost of a coil constructed similar to his ?—Wreath,

[4566.] —UMBRELLA FRAMES. —Can any of my, brother readers tell me how the steel ribs and stretchers for uinbrolla frames are made? also how much capital would be required to start a small business ?—Alpha.

[4567.] —MATHEMATICAL INSTRUMENTS. —Can any reader favour me with practical directions for fitting and fastening the steelloaves used in making the joints of mathematical drawing instruments? I believe they are soldered or braxed in, but am ignorant of the process, and wish to replace somo of my present set which have been lost.—S. Stevens.

[4568.]— WEIGHT OF RAILS.—Can any fellow subscriber oblige mo with a rule to find the weight per vard of rails of various sections (iron or steel), whether Tees, Doubleheads, or Bridge rails? I can readily find the weight of round, square, or flat bars, but find very great difficulty in finding the weight of rails from the tracings which accompany the orders.— Ferrum.

[4569.]—ESCAPE OF GAS.—Can any of your numerous correspondents account for the following phenomenon ?—At the end of last winter we had about 20,000 feet of gas left inour'ometer. To preserve this we filled the pipes with water, so that nothing could possibly escapo either by the inlet or outlet pipes. We are confident there Is no leakage at the centre or anywhere else, still the gas has gone ; we have not 5,000ft. left today. Can anv one give a natural or scientific reason why it is so ?—W. C.

[4570.]—A LEGAL POINT.—Can any of your many readers inform me of the real meaning of the law in reference to buying and exchanging old metals. I am an ironmonger in the country, and often get old metals brought to be exchanged for new goods. The police here inform me that I oan neither take in exchange nor buy any less quantity than | cwt. at a time, and that if I have to supply a customer with a new copper furnace, I cannot take tho old one unless it exceeds tbn above weight. Is such really tho absurd wording of the law, or have the wise heads of our officious local police misconstrued tho meaning and intontiou of the Act? Any information on the subject will bo verv acceptable to many in the trade, but more particularly to—IRONMONGER.

T4571.] RUBBINGS.—Is there any better way of taking rubbings of coins than by using the hcolball sold by shoemakers.—W. J. Eoolsston,

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4135 Steaming Bottles, p 358.

4138 Designs for Stamping Tea-trays 358.

4139 Stains in Veener, 858.

4140 Foreign Carmine, 858.

4143 Dyeing Woollen Carpets, 858.

■4152 Manufacturing Gas from Vegetable Substances,

858. 4157 Reed Organ. 858.

4161 Refrigerator, 858.

4162 Strengthening Steel Wire, 858.
4164 Slits in Steel Gauges, 358.
4170 Smoke Burning, 858.

4172 Boring Bar, 358.
4179 Crayon Drawings, 358.
4184 Lathe Work, 869.

4186 Sheathing Iron Ships with Copper, 859.

4187 and 4258 Steam Carriages. To G. Plow, 359. 4190 Emigration to the Cape and West Indies, 359.

4196 Cement for Fastening Brass Caps to Bottles, 359.

4197 Warming by Hot Water, 359.
4200 Precipitating Cochineal, 859.
4203 Paris, 382.

Naval Architecture, S82.M82
Black Diamonds for Drilling, 382.
Adulteration, 882.
Water-wheel, 382.,
Sign Writing 882.
Harmonium Reeds, 882.
Photography, 882.

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4224 Treatment of a Chrysalis, 382.

4232 Unnoticed Queries on Magnetism, 382. Iffl,

4289 Medical Coil, 882.

-1240 Watchmaking, 882.

4242 Incrustation in Boilers, 382.

4343 Wire Netting Machine. S82.

4246 Glycerine as a Substitute for Cod Liver Oil, 383.

Anatomical Models, 383.

Paint for Aquarium, 383.

Gold Lacquer, 383.

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ANSWERS TO CORRESPONDENTS.

♦»* All communications should be addressed to the Editor of the English Mechanic, 81, Tavistockstreet, Covent Garden, W.C.

R. F., W. 4 S., S. O., T. W. W., W. E. Mavcrly, Thinker, John Bell, Beacon Luff, J. H. B., Sergiurs, J. H. P., J. H., T. E. Graham, Goo. Jackson, Frank Chessell, R. D., B. B., Operator, J. W. Cox, G. Buck R. T., J. Haines, W. D., E. J. Lay, G. W., T. W. Phillips, A Subscriber, Exhibitor at Royal College o( Science, J. T„ A Poor Mechanic, W. Airoy, Verturnnus, Studeut, J. H. T., Kevd. J. H., An Engraver.

B. E. Loddy And Youso Jodbeb.—" Second's Practical Watchmaker," in a letter, says:—" I shall be pleased occasionally to reply to such queries as may be iu my power to answer."

H. Pocklinoton.—Thanks. Please send the MS.

E. L. G.—Your other excellent answers next week.
Kensingtonian.—Suggestion not practical.

The Microscope.—Q. Sea says, "I am pleased to seo that we are to have some information ou microscopic subjects. The telescope and bicycles have had their share of space. I hope some friend will give a list of objects easily obtainable and how to mount them."

W. R. Birt.—" Telescopic work for moonlight evenings," next week.

F. H. S., Dewsbdry, is of opinion there is want of an English Mechanic Improvement Society in his town. Let him, by all means, then, do what he can to establish one.

Kbnsinotonian.— The pump, or its connection with

the well, must be out of order. M. J. Whxatley.—Mr. Baskerville's letter on link

motion was in type before vours came. Velocipede.—We don't seo now your suggestion would

"get or gain speed;" besides it would increase the

weight of the machine. An Upper Foreman.—Is there any need of such a

society? Ask some of your confrere*. Henry Monro.—Your answer to " Sabbas" as to a good

microscope is au advertisement, and, therefore, not

inserted. We have decided not to insert replies in

future with recommendations and [prices of articles.

We have known instances where Questions have hupn

CONGRATULATIONS & TESTIMONIES

(<Joniinu<d from page 408.)

04 "The whole forms a most valuable and iastrc-a, publication for all who delight in scieuc*."— Mar<^, New/paper.

95 "The English Mechanic, with its »*-*! illustration and fund of information, is almost T by its bulk."—Leamington Courier.

96 "To those who are anxious to know who:* ;, done with pence wo suggest the postage of 11 srj,.,., the Tavistock-street office for the current nwarW.i and wc aro suro that astonishment will only cWr * pleasure in turning over the pages of this joasWiEvention."—Hackney andKingtland Gazette*

EMPLOYMENT COLUMN. We have frequently been asked t o devote a portion of our space to cheap or rather SMALL Wanted Advertisements, and we now propose to do so under the heading "Employment Column." Hundreds of skilled labourers are continually wanting employment, and very frequently employers are in wont of skilled labour. These wants, in a great industrial country like ours, exist under a variety of forms. A brass-founder may want a foreman; or an optician an assistant; a person may want his microscope repaired, his pianoforte tuned, or his manu. scripts edited, when in all probability there is just the person to do the work near by. But the two do not know of each other's wants. At the present time there is no national cheap and expeditious medium whereby the one who wants the work done, and the other who Is ready and able to do it, may easily place themselves in communication with each other. We think the Enolish Mechanic is just the organ for such a purpose. This, in most cases, may be done in a very few words. We therefore place at the disposal of all who may wont it,

OUR EMPLOYMENT COLUMN. As in the Sixpenny Sale Column, the chargo will be sixponco for the first sixteen words, and sixpence for every additional eight words.

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e have known instances where questions have been asked Bo that an advertisement in the shape of an answer might appear. The Microscope.—Thanks. "An Axmouth Resident" says, "Allow me, through the medium of our MeChanic, to thauk Mr. Pocklington for his kind and courteous reply (1831, and also for his promised information on 'How to Choose and I How to Work tho Microscope,' which I have no doubt will be highly appreciated by many an amateur reader." 8. A. R.—See back numbers. A description and illustration of the Mitrailleuse are given in this number. W.harrold.—Evidently the kail mark. Pattern Maker.—There is no quick method of learning to read and work from mechanical drawings. Practice and attention will alone help you. Tojieter.—The Patent Office Library, 27, Southamptonbuildings, Chancery-lane, is free every day to the public, and contains many valuable scientific books. H. Holderness.—For the second time we have to ask you to read the journal before you complain of the non-insertion of your communication. Your query was inserted on page 455 (No. 4406). Bonnet.—We cannot advertise manufactuiers of lifting

jacks gratis. P. G. Greville.—Questions are selected for Insertion not solely for the benefit of the individual questioner, but for our readers generally. We will willingly insert any information which you or Mr. Coffey in reference to his patent (? 4424) may send. Our correspondents are too numerous to keep their addresses. J. H. 8.—Your suggested improvement of the bicycle is insignificant—if, in fact, it is an improvement at all: J. H. L. says:—° No doubt others have congratulated you on the incorporation of the British and Foreign Mechanic, but I think, Sir, you ought to be congratulated on your moderation in the hour of victory. It so happens I .know how you were treated about twelve months since. As you have not related the story, I shall not, much as I am tempted to do so. You have permitted the originator and editor of 'the would-be rival,' to pass into contemptuous obscurity, without a parting kick, although you have all the field to yourself." E. M. D.—Agree with thine adversary quickly. J. Bull.—See par.—sixpenny advertisements. Florist.—You may kill aphides on geraniums, fuchsias, and various other plants, by dipping them bodily into hot water. The temperature must not be above 140° Fahr., or the tender shoots will be destroyed.

B. Y.—Order through a bookseller.
J. H. W.—Answer through our columns.
E. West.—Dr. Ussher fully described the American

organs in Nos. 225 and 239.

A Ledger.—Write to L. Olrick, 27, Leadenhall-street.

J. H.—The curlew may be found feeding on mud flats at the mouths of harbours about this time. It is an excellent bird for the table, although rather out of fashion.

Spero.—See reply 4438.

C. Hudson.—You can buy fret saws cheaper than you can make them.

May And Mountain—Send drawings if you like.

Salt-water Aquarium—G. P.—Yes. It is quite possible to keep marine animals alive for some months in ordinary glass tanks. Anemones, hermit crabs, limpets, small mussels, winkles, shrimps, 4c., will live a considerable time if the water is properly aerated. Fit a piece of slate in so as to vary the depths; and oyster shells may be fixed to the sides by gutta-percha to act as ledges. The greater portion of the light should be excluded by covering the side nearest the window with thick paper You can obtain sea-water in London at 3d. per gallon.

One Op The Firm or B.—We do not remember your former letter. You should have repeated your your question.

T. W. Wedlake.—We can give no other information than appears hi the article.

97 "Your journal, with its moderate jt» ud excellent information, is a great boon to t£r peek H. N. Hcmphheys, Gas Works, New Boras.

98 "The best and most useful iourwilers reti: T. O'brien, North Wall, Dublin.

99 "Nearly all the members of the C'Waf Astronomical Society are readers of your w »nM« journal."—William F. Denning, Hon. Sswiwir. Astronomical Society, Ashley-roachBristoL

100 The Rev. Dr. Gibbes, Plymouth, in aleinna Editor, says ho weekly eagerly expects, boroj reads with great satisfaction, the English Heebie

101 "While I am writing, I cannot forbear «y^. word as to the wonderful improvement of the Emit; Mechanic. You must be satiated with congratuUfej; on this subjeot, but we subscribers must comrratiiU^ ourselves. Your latest incorporation will render it tl ditionally valuable and interesting. I have often beet struck, in comparing the quality of tho questions sad contributions, with the immense progress they have mode since I first became a subscriber—soon after Hi commencement. This is at ttaet as noticeable in astronomical and cognate subject* as in any other branch of science which has been treated of. I am sure this flows mainly from the educational power ol the Mechanic. The influx of such names as Proctor, Webh, Lockyer. Birt, 4c—not to forget all the other learned thoojdi anonymous contributors—has given your editorship to* character of quite an era in the history, and a warrant for additional success, of your estimable jonrnaL"-r. H. Bcpfham, Earith, Hunts, July 12.

102 " Within less than four months yon have ten? nated the individual' career of three publication* rr i> sorbing them into yourself. I have had someenaxs? of journalism, but I never saw a speedier and an^ex change for the better than has been eihSiWfriSi English Mechanic. Yon have enlarged rx au sad improved your type; you give better paps-JeaiauroTel engravings ; you have multiplied your srreneBAefti. as you have certainly widened the scope sM ^sryese at your journal."—Suburban.

103 "I hail the arrival of your most comprobart journal as oneof the greatest pleasures of the wettci must add my testimony to tho seal and ability « which it is conducted."—H. D. Crozier, Captain, Esf>i Engineers, Gibraltar.

104 " Quite a mine of intellectual « faith. What i satisfaction it must be to your numerous scientific eerre spondents to act on the give-anl-l* ke principle, and «■

assist each other in substan ial improvement-" J. D

Seymour, Albion, Broadst lirs.

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105 "The absorption of Scientific Opinion, and Us British and Foreign Mechanic must have increased yoc already va6t circulation, and proportionately augment,*. your influence in the country."—Jas. Harris, Garlinge, near Margate.

106 "The great' and increasing success of the EngLish Mechanic, which has grown from an acorn to aa oak tree, is the best guarantee that scientific inatrnctira is making rapid progress in the country. For years p»_=t we have had widely circulated and extensively re»il newspapers and religions publications ; now we have as ably edited, many sided, and numerously read uriejattA: journal."—A New Subscriber.

107 "It is as engrossing as a romance to the lover •! practical engineering. It is half full of pictures of mechanical and scientific apparatus, and the other half i* a, concentration of scientific knowledge."—IUuttrataal Mi<il tnd News.

108 "Its chief charm is that its subscribers are axten bers of a universal instruction society."—Thos. Wbexj,s

109 "There is something in it for the engineer, tlie* chemist, the microscopist, the electrician, the lover of natural history, tho astronomer; in fact, for tho stxadcrst. of all branches of science.—Samuel Jokes,

®Itq (fmjltslt Palmitic

AND

MIRROR OF SCIENCE AND ART.

FRIDAY, AUGUST 26, 1870.

SATURN.

By A. Fellow Of The Royal Astuonomic.il

Society.

(Continued from page 506.)

THE ellipticity of the disc of the planet itself, as in the case of that of Jupiter, strikes the eye the moment it is applied to the telescope. On April 19, and later, in May, 1805, Sir William Herschel, examining Saturn with reflecting telescopes of various apertures and focal lengths, thought that it presented a figure " somewhat like a parallelogram, with the four corners rounded off deeply, but not so much as to bring it to a spheroid;" and that very eccentric writer, but assiduous star-gazer, the late Dr. Kitchener, in his singular omnium gatherum on "The Telescope," states that he witnessed something of the same appearance in September, 1818, with a 3-tnn. achromatic of 46in., and a 4in. achromatic of 10ft. focus. The most elaborate micrometrical measurements, however, made by Bessel in 1833, and repeated by the present Radclitte observer, the Rev. R. Main, F.R.8., at the Royal Observatory, in 1848, go to show that this effect is probably referable to some optical illusion, and that Saturn is, in reality, an exact spheroid of revolution of considerable ellipticity. The compression adopted in the "Nautical Almanac " is polar semi-diameter = equatorial semi-diamoter X -927. Like Jupiter, the ball of Saturn is diversified by dusky bands or belts, which are very variable in their aspect. Ball, of whom we have before spoken, saw them as early as 1656 ; Cassini noticed two Borne nineteen years later; and Herschel, who devoted great attention to them, saw sometimes only two and sometimes more. In 1793, he observed a quintuple banding consisting of three dark and two intermediate bright spaces. He also remarked the dusky hue of the planet's poles, which is, however, a very obvious and persistent phenomenon. By a careful and prolonged examination of various serial changes which occurred in those "belts," Herschel at first fixed the time of Saturn's rotation at lOh. 16m. 0-4s., and afterwards at lOh. 29m. 16-8s.; Schroter gave a longer period, but the exact one must be considered as still tubjudice. This banding of the planet is doubtless atmospheric, and may be held to be the analogue of our terrestrial trade winds, save that from the enormous velocity with which Saturn rotates on his axis, they must blow parallel to his equator, and not as our own do (so to speak) diagonally. The spectroscope indicates a very marked resemblance between the Saturnian atmosphere and that of the earth. Under favourable circumstances, the dark shadows cast by the rings may be seen on the body of the planet, and of course that of the planet on the rings. A little sustained attention, too, will sometimes show that the globe is not absolutely central in the ring. This is, however, by no means always to be seen. Micrometric measures make the dark opening a very little larger on the east side.

The subjoined view, drawn expressly for this essay, ad naturam, represents Saturn as he appeared in a 4 {in. achromatic telescope, with a power of 250, on the night of June 21,1870, at; lOh. Mm. Greenwich mean time, and will serve to illus

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planet, only some 16° above the horizon when on tho meridian, would effectually preclude the chance of perceiving it. Next, Ball's great division will be noticed, extending right round the ring and passing at a marked and notable distance above the planet's north pole (below in the picture, which was of course drawn with an inverting telescope). We then arrive at the broad bright ring B, which shines with a purity and brilliancy contrasting curiously with the dull appearance of ring A, on the one hand, and with the yellow tint of the globe on the other. The faint shading on its inner edge, at the extremities of the major axis of the ellipse which it forms will be observed. And then travelling onwards we find the crape ring C, which, on the night when our drawing was made was of a brightish slate colour. Its tint is not, however; always uniform—nay, it sometimes varies in the two ansa?. It will strike the observer, when he has once fairly got this very wonderful object in view, how much too narrow the portion of it which crosses the ball appears in comparison with those parts of it in the amp. None of the engravings with which we are familiar give this curious effect. In all which we have seen the dark ring is represented as far too broad where it crosses the globe of Saturn, and proportionally too narrow in the answer. Returning, however, to our own sketch, the marked ellipticity of the globe will be palpable to the student. He will also notice the bright equatorial belt, succeeded by a narrow dark one; that again by a narrow bright one, north of which a dusky capping extends right up to the pole. The shape of the shadow on the ring B will be remarked too, and the fact of its terminating in, or becoming indistinguishable from, Ball's division.

We have taken care, as far as possible, to present a facsimile of what we saw at the date referred to above, in order that our readers who may be in possession of instruments of 4in., er thereabouts, in aperture, may know exactly what sort of view of Saturn they may expect, should their telescopes be of adequate goodness. In fact, it may be considered as a kind of test view of the planet in its present position, as the achromatic employed in this observation is one of the very highest excellence; and we have shown absolutely nothing but what was seen at the epoch of the drawing. In most of the modern books on Astronomy, most exquisite pictures—or fancy portraits-^-of Saturn are given; but these are made up by piecing together B quantity of detail never seen in conjunction at any one time.

Turn we now to the satellites, with which this planet is more richly endowed than any other member of the Solar System,—no less than eight circulating about him. The largest of these (the sixth, reckoning outwardly from Saturn),Titan,was first discovered by Huygens, on March 25,1655. It is a very easy object to discern; it may almost always be picked up in the finder of an ordinary telescope on a dark night. The moon exterior to it, Japetus, is also pretty bright, especially at its western elongation. It was first seen by Cassini, in October, 1671. The same astronomers detected the three more minute satellites, now called Tethys, Dione, and Rhea, between the years 1672 and 1684. From this time until 1789, it was believed that no more satellites than these five existed; but on August 28th in that year, Sir William Herschel picked up another; and on the 17th of the following September, yet one more. These two interior moons are now known as Mimas and Enceladus. It was now imagined that no more moons remained to be discovered, and we find in works published as recently as "The Penny Cyclopedia," the statement that Saturn has only seven of these attendants. It is, however, most remarkable that an eighth was discovered on the very same night, September, 19,1848, by Mr. Bond, in America, and by Mr. Lassell, at Liverpool; it has been called Hyperion, and is situated between Titan and Iapetus. We append some details with regard to these satellites in a tabular form.

trato many of the remarks which we have been making. The darker tint of the outer ring A, will be noticed. No division in it is perceptible, but even were this always seen (instead of, as in fact, very seldom) the present position of the

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apparently travels to a considerable distance from Saturn, and whose orbit, unlike that of the other satellites, is inclined perceptftly to the plane of the ring, may also be readily seen; at all events, when it is situated to the west of the planet. Rhea usually looks something like a (standard) 9'4 magnitude star, but is sometimes brighter, and sometimes not so bright as this. Tethys and Dione are both very faint objects; the latter resembling a standard 11- magnitude, and the former being even fainter than this. They require a first-class telescope and acute vision to see them fairly. Mimas and Enceladus are both beyond the reach of all ordinary instruments, and we need scarcely add that Hyperion is hopelessly so. Transits of Titan over the disc of the planet, where it appears as a black spot, have been seen by Sir William Herschel, on November 2, 1789; by Gruithuisen, in 1833; by Dawes, on April 15, 1862; and by Mr. Gorton on the same night, with a telescope of 3S aperture; while Mr. Banks actually saw it easily tcith a 2j/n. object-glms. Webb and others also observed it. Dawes witnessed another transit on May 17, in the same year; and on the 25th of that month he watched the immersion of Titan into the shadow of Saturn. Having thus detailed the principal appearances presented by this grand system, we may very shortlv endenvonr to decipher their significance, and to ---„ it we can 2nd any plausible theory to a<!^.-^nt for them. And, lr the outset, we have ..ever opened a book treating o f the planetary system which did not contain the statement—or some equivalent one—that " the density of Saturn is about that of cork." Now this assertion can only be made upon the assumption that it is the outline of the solid body of the planet which we are looking at; whereas, as must be perfectly obvious from the shifting belts, &c, we are regarding his atmospheric envelope, which may be, and must likely is, of great height and volume. It is also necessary to assume that the globe of Saturn is solid throughout, of which we have not the shadow of it proof. It is then quite credible that the actual structure and density of the planet itself may not differ to any very great extent from those of our own earth, and if this be the case, the vaporous atmosphere would retain sufficient heat, by stopping radiation, to enable people, constituted in no material respect differently from ourselves, to live there.

But what are the rings? Ay, what are they? The answer to this question is by no means so simple as it would appear; and our first difficulty arises in this wise. There is a limit to the cohesion of every known substance. If we tried to model Mont Blanc of its natural size, in jelly, the whole structure would be crushed down flat" from its own weight; while it would be obviously impossible to spauthe Straits of Dover by a single 'arch of any conceivable material. What then must be the coustitutiou of the stupendous circles of light of which we are speaking? whatever it may be, it was shown by La Place, in his "Theorv of Saturn's Ring," in the Memoirs of the Academy of Paris for 1787, that what appear to us as single rings must consist of numerous concentric ones, "and that a rapid motion of rotation round their central axis was essential to the stability of the system. More recently it has been demonstrated by the American Professor Pierce, and after him bv Messrs. J. Clerk Maxwell and R. A. Proctor, that even La Place's numerous rings will not rigorously satisfy the conditions of stability, and that it is in a much higher degree probable that these most wonderful luminous hoops are made up of thousands and thousands of minute satellites so closely packed as to affect our eyes with the impression that they form solid plates! Still, this occult question can scarcely be said to be definitely settled, and we can only accept this hypothesis provisionally, as, on "the whole, the most plausible that has ever been advanced.

Any notice of this nature would be incomplete • without a reference to one of the ablest astronomical monographs which have appeared during the present century,—a work by which its author, previously absolutely unknown beyond the walls of his dim university, acquired, per taltum, a European reputation,—we mean, of course, "Satur:> and its System," by Mr. R. A. Proctor, B.A., F.R.A.S., &O., the familiar contributor to these columns. It would not be going too far to assert that it is impossible to understand the Saturnian system properly without a perusal of the book referred to, and we would in all sincerity counsel every one whom our cursory remarks may have interested in the subject, forthwith to pro

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