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their making scratches on the thicker parts of some 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.

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 useful cell made.-OPERATOR.

[4434.]—TAPS AND DIES.-W. Reed can make left-rings answer extremely well; in fact, they are the most handed taps and dies very easily: he has only to work them the other way or backwards.-SEMPER PARATUS. [4439.]-MATHER & PLATT'S PATENT PISTON. "C. S. A." should write to Mather & Platt 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. The address of Mather & Platt, engineers, is Salford, Lancashire.-WAHSROF.

55° 56°

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[4441.]-BAROMETER.-I must ask "Junius" to examine the index closely, and he will find that the degrees of temperature increase in a direction opposite to the tube graduations on circle d d d, so that as the temperature rises the liquid falls and the ratio in my glass is 4in. for 1° Fahr. more or less, thus: e.g. 54° Fahr. = 6 inches' = 5.6 19 Barometer steady at 30.5 =5+2 = 2.8 "3 This must be found by experiment for each glass, and it is only necessary to select a day when pressure is steady. Having inscribed your circle d d d as directed, place a blank circular card therein, and mark on the margin the temperature at that time. This figure must of course coincide with the liquid level on d d d. An hour after the temperature will have probably altered 1° Fahr. more or less. Set down this new number opposite its reading on d d d. A certain interval of tenths will be

62°

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[4449.]-RESTORING FRESHNESS TO FILTERED WATER. The flatness of the 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 press. An ordinary copying press will answer well. Sulphur and white wax are also used; and for small coins, ordinary sealing 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 use as follows:-Grease the coin and fix a cardboard ring round the coin, and then pour in the wax, melted; when it has set, take it off and re

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found for 12; 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 for its insertion. If "Junius" fails now I will draw out an index for him. -CORNUBIA.

[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. He 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 the gas tar, with old lime, broken bricks, bits of limestone rock, Derbyshire spar, &c., to taste, and then 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 habit of going to smash. Their natural end seems to be diffusion. If, however, "H. U." wishes to try the experiment of mounting them, he had better use Thwaite's liquid, or glycerine and camphor water. Pumphrey's vulcanite cells are so cheap (1s. per 100) that no excuse exists for trying rubberings. 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 mount a rotifer so as to keep well, without causing a great alteration in its appearance. Try one in Dean'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

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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.

[4453.]-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 bleaching and printing works that, though they use the steam for boiling, &c., 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 & Son, or Messrs. Hick, Hargreaves, & Co., of Bolton, make what are considered very capital reducing valves.WAHSROF.

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

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[4458.]-BLACKING FOR HARNESS.-The following recipe is given by good authority:-Treacle, lb.; lampblack, loz.; yeast, a spoonful; sugar candy, olive oil, gum tragacanth, 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.

is said to be good:-1st, Soft water, a gallon; soap, [4459.] FURNITURE CREAM. The following and add 2oz. of pearlash. 4oz.; white wax in shavings llb. Boil together, To be diluted with water, laid on 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. M.

[4451.] MOULDS OF COINS.-White wax, with flake white added, gives very good impressions of gummed round their edges, to hold the wax when poured coins, &c., which should have a narrow slip of paper in a melted state on them. These should, when cold, camel's hair pencil till the whole surface of the wax be coated with plumbago, applied in powder by a assumes a polished appearance.-J. B.

[4451.]-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 of a thickness to suit the coin or medal to be copied and steep it in warm water until it becomes soft, and simply place a 141b. weight upon it. This does one side then warm the medal and lay it on the gutta-percha, and only the same is required for the other. I then rub the 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.

[4459.]-WHITE FURNITURE CREAM.-Take of raw linseed oil 6oz.; white wine vinegar, 3oz.; methylated spirit, 3oz.; butter of antimony, oz.; mix the linseed oil, with the vinegar by degrees, and shake well so as to prevent separation; add the spirit and antimony, and mix thoroughly.-R. S. NEILSON.

4461.]-SCREW CUTTING.-In answer to "H. Williams," I should use wheels of 12 gauge, provided they can go on to the mandrel, in which case the distance between the centre of mandrel and centre of leading screw would be about 7in. If his lathe has only one collar, and a cone 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 then 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 screw that I am now putting to my old 5in. lathe in place of one of 10 to an inch that I find too slow for what I now require, only my new screw is of double thread, cut with a screw tool of pitch. I have nearly done my new double-geared 5in. head stock, and shall show it with pleasure to any one who wishes to see it and will first address a letter to me per the Editor ENGLISH MECHANIC.-J. K. P.

[4451.]-MOULDS OF COINS.-If it be required to produce moulds of coins so as to obtain facsimiles in electrotype copper, the best plan is to make impressions in sealing wax on note paper, then, to avoid warping, attach them to a heated copper wire, and then thoroughly blacklead 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 close together on the 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 silvered 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 of not injuring the surface, which can hardly be said for stearine and spermacetti, &c.-W. K. B. [4452.]-LIGHTNING CONDUCTORS.-Rod iron is generally used for them. A good size is in. They should reach above the highest part of the building, and be pointed at the top. The points of contact with the

[4462.]-STRANGE PHENOMENON.-The phenomenon described proves that "Glowworm" is one of those few persons that are capable of being affected by, or sensitive to, odic force. I should feel obliged if "Glowworm," if he has a chance, would experiment a little on the 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 night, so as to exclude every trace of light, and placing himself about a foot say half an hour-and also note the phenomena that take from the magnet look at it attentively for some timeplace. I shall feel obliged by these simple experiments the truth of a little known and despised branch of being tried by "Glowworm," as they will help to confirm 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 the leaves. I can, if required, name many places where the new-made grave it is above light will be seen; over a very often seen, and no doubt has frightened sensitive people terribly, while another person not sensitive would not be 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 the ENGLISH MECHANIC, and, by your courtesy, an occasional contributor to the correspondence. The manganese battery continues to work perfectly well, and untouched for many months, with the exception of an hardly diminishes in strength. It has been absolutely occasional addition of water to replace evaporation: The clock keeps better time than a good pocket chronometer in my possession.-W. H. STONE.

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

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[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 a quarter of a pint of spirits of turpentine. Wash one side of the paper by being with this mixture. The black carbonic papers are made painted" with a composition consisting of 2oz. of tallow, Joz. powdered blacklead, pint of linseed oil, and sufficient lampblack to make it of the consistency of cream. These should be melted together and rubbed on the paper whilst hot. When perfectly dry they will be fit for use.-C. T. R.

[4466.]-CLEANING PRINTS.-Immerse the print in a bath made by adding to strong muriatic acid its own weight in water, and to three parts of this mixture putting one of red oxide of manganese. A print may remain in this liquid 24 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.-SABBAS. [4467.]-IMPRESSIONS FROM PRINTS.-I give the following recipe, but I have not proved it:-Soak the print in a solution of potash, and afterwards in one of tartaric 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, except in those parts to which the ink had been originally applied. The ink of the print prevents the penetration of the saline matter, and so only the lines of the picture will take the ink from the

roller.-C. T. R.

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

QUERIES.

FOR SPA

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 LATHES.-Could some of your readers kindly
[4514.] -STEEL MANDRELS
no change in the chemical or galvanometric results. I
do not at the moment see how to assist R. N." in gain-collars or bearings and hardening the same tr
turner the best means of forming steel mu
ing his object The tangent galvanometer will be fully lathes ?-JOHN THOMAS.
described in my next paper. The British unit is about
one twenty-fifth of Varley's.-SIGMA.

[4494.]-DISSOLVING RESIN.-You need not dissolve the resin; add to the flour with which you intend to make your paste 1-6 to 4 of its weight of very finely powdered resin and proceed as usual; this with the addition, when made of a minute quantity of creosote, oil of cloves, or corrosive sublimate, will keep a long time. T. W. BOORD.

silver articles, when tarnished, may be cleaned by

[4500.] - SILVER THIMBLES.-These and other washing with caustic ammonia.-T. W. BOORD. [4503. MENSURATION OF SUPERFICIES.-The area of "T. W. H.'s" triangle is 20-6197, and the following is the manner of working it :9-275+ 5.5

-=11·1

2

9.2 = 19

11.1 11.1 7.5

[4478.]-BLUE WRITING INK OR FLUID.-One of the best and simplest is made by dissolving soluble prussian blue in distilled water. The blue is obtained by adding a solution of proto-sulphate of iron to a solution of ferroyanide of potassium and washing the precipitate, after it has acquired a deep blue colour, until it begins 111 x19 × 36 × 56 = 425-1724 to dissolve in the water; it inay then be either collected and dried, or at once dissolved for use.-T. W. BOORD.

[4479.]-COLLODION.-In order to avoid ridges when coating the plate, it should be rocked to and fro while the superfluous collodion is draining off into the bottle. I should think that W. Crawley's collodion is too thick.-T. W. BOORD.

= 36 11.1 - 5.5 5.6

425 1724(20-6197

4

406 02517 6) 2436

4121

41229

8124 4121

400300

9 871061

412387) 2923900

2886709

[4481.]-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 full inches in the ratio that the lower mercury surface is less than both surfaces together. Rarely is the tube so small relatively J. NASH. to the cistern that a variation in the difference [4506.1-WATER BAROMETER.-I should be glad to of level would practically be all visible at the help "Gimel" without price, but glass is perishable, and scale. If its inches then are not diminished, I should a journey would be fatal to such a fragile arrangement; conclude the original designers contemplated this very besides, each glass requires at first a careful series of clumsy adjustment of level at every reading.-E. L. G. observations in order to construct its index (see reply [4482.]-OVAL.-The following method of describing would easily construct the glass from the drawing, and to "Junius" in this number). Any handy workman anegg-shaped oval" is taken from "Burchett's Prac-if "Gimel" could spare ten minutes a day for a week, he tical Geometry"-a ufficient answer to the second would get the range, and could form index therefrom.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 semicircle, cut the right line in A and B. From A and B, with radius BC, describe arcs CE and DF. From A or B draw a right line through the transverse diameter, cutting it in G, touching the opposite are in E or F. From G, with radius GE, describe arc EF, completing the figure. NOTE.-The length of the figure may be increased or diminished by increasing or diminishing the radii AD and EC, and by placing the point G higher or

lower on the transverse diameter.-J. NASH.

CORNUBIA.

[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 less quantity of dung would do if the mould used is full of fibre-like turfs cut from an old meadow. But will not the temperature on the top of the boiler be rather too high ?-SAUL RYMEA. [4509.]-BRASS TUBES.-Brass may be polished with crocus and oil after 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. BOORD.

[4511].-WEIGHT OF BALL.-To obtain the weight of a cast-iron ball multiply the cube of diameter in inches by 156. For wrought iron multiply by 146, which will give the weight in lbs. To find how much wire fin. round can be made from a ball 7in. diameter, first find the weight of a yard of the wire by multiplying the square of diameter by 7854, which gives the weight per yard in lb. Then divide the weight of 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 "Ralph Williams" will find the weight of a wroughtiron ball, 7in. diameter, to be 50lb., and the weight of a yard of fin. round wire about half a pound. Therefore 100 yards.-FERRUM.

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[4482.]-OVAL.-Works of high geometry, as Sir Isaac Newton's "Enumeratio Linearum Tertii Ordinis," describe plenty of geometrical curves more or less eggshaped-as that described by a point in the connecting red, Fig. 1, p. 448 (July 29), but all such ovals, being of equations above the second order, are beyond treatment in popular books. If the question be one of mere drawing, the outline of a hen's egg is best represented, Mr. Denison says, in his " Astronomy without Mathematics," by a semi-ellipse for the small end, joined to a semicircle for the large. Many more elegant ones, as the plover's, are rather composed, I think, of a parabola with a circular arc, which in that case must always be more than the 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 that no ellipse, visibly or plainly different from a circle, cau be decently imitated by fewer than eight circular arcs. The arches of old Blackfriars Bridge might have only four, but few probably noticed that they were oval at all. The Roman amphitheatres were, as may be seen by all foreign plans of them, all A simpler rule, though not so exact, is: 9 times the cube of struck from eight centres at least-never from four-as the diameter, dividel by 64, will give the weight in engraved in one of Mr. Fergusson's books, or like the pounds. So, Kensington Hall of Science. In fact, no race that has anywhere leit monuments, before the English of this reign, ever tolerated anything like the crippled fourcentred ovals of our builders. The Victorian loss of "eye," or sudden barbarizing, in one generation of all taste in form or colour among us, is a really new and world-wide nuisance, one that, though accounted for, will make the age stink to all others while a relic of it lasts.-E. L. G.

[4487.)-BURNT CLAY.-The red colour is due to the decomposition of salts of iron during the process of burning.-T. W. BOORD.

[4489.]-TURNING COPPER.-Reduce the width of the cutting edge of the tool.-T. W. BOORD.

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

[4511.]-WEIGHT OF BALL.-An iron ball 7in. diameter would weigh 49 6521b.; for the weight of a cubic foot of cast iron is 7645oz. Avoir. (Hutton), and the cubic content of a ball 7in diameter is 179 5918 cubic inches. The following formula will show the working:78 x *5236 × 7645 1728 × 16

73 x 9 64

= 49-652 +

= 48-234375

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[4515.]-FELT HATS.-Would any brother form me how to clean felt hats when they get er shiny ?-IGNORANCE. [4516.] ASTRONOMICAL PHENOMENA-E "F.R.A.S." or Mr. Webb kindly give an opinim following? A young friend of mine write to mor follows:-"The moon was very low, being only Fam the house at the end of the garden *** it was exactly as if a continual current of air mang sionally with the position of objects, but no ad off the north edge of the lunar disc, inlede with their sharpness, but quite prevented vary and a jects being seen. A power of 540 showedway vibration." My friend's stand is of mixed garag and, though portable before some sa was, I know, quite steady. The house atie van de fe garden is distant about 120 yards; th stands usually about 100 yards from Whether it is to vibration of the stand.%ærend air arising from the roof of the house, i àa URSE MINORIS.

[4517.]-STAINING GUT FISHING LIV-743 the best stain for gut lines, and how can Ipan FLUVIUS.

[4518.]-MYROBALANS.-What is myria for what is it used?-H. U.

[4519.]-PHOTOGRAPHY.-Can any of our

readers inform me of a varnish that will pre negative while printing, and not stick to the pat would prefer one that requires heat to vandent any one could tell me how to make it I should be ea. -YOUNG PHOTO.

[4520.]-PERCH FISHING.-When is the best time to fish for perch, and what is considered the prop tackle ? Are there any good perch near London *EDWIN JONES.

[4521]-EXTRACTING HONEY FROM THE COME. -Can any of your numerous correspondents enlighten me as to the best way of extracting the honey from the comb, for domestic use?-AMATEUR BLE KESPER

[4522]-PURE CHARCOAL-Ishould feel obliged ? Sigina" would tell me how to make pare charcoal, an what kind of fire and hot plate is pare.-SAMUEL IBBOTSON.

[4523.]-COLOURS FOR TICKET WRITING.-C any brother reader kindly inform me what ingrediens are used, and the way of mixing the following colours as used by ticket writers-red, green, brown, and fe low ?-COLOURMAN.

[4524.]-STEAM JOINT.-I have a portable foil
boiler, and I wish to have one or two fixed engines A
different parts of my farm, and also to have a parti
Cameron's steam pump. In fact, I want to ca
boiler to where I have an engine or pump instal
portable combined engine and boiler. The dir!
have is to get a perfectly tight steam job
boiler and engine. As with a portable b
be almost impossible, having regard ag
ground and any slight change of place it, to keep
the joints of steam pipe tight. The accid
tube vulcanized, but I am afraid that te te MED
be met temporarily by the use of a fie rubber

at a pressure of 80lb. to 100lb. per inca vald in a few
weeks destroy the india-rubber. Can we ne
readers tell me whether any telescopic
vertical motion, and motions right and da
from engine has ever been used, and if so, what is
be got ?-SCHEMER.

[4525.]-VESUVIANS.-Will some reader oblia D with a recipe to make vesuvians and cigar hetalJ. B.

any obliging scientific or other re der of Lae Mecha [4526.]-ELECTRIC TIME GUN AND BALL give me a description of an electrical time gun sei -I mean a model on the same pr c.ple as that k perimented with on the lecture table, and wish vẽ, Edinburgh or Birkenhead, &c.? I ave seen then much to construct one myself.-W. E.TH.

[4527.)-AERATED WATERS.-C. n any one we quainted with the manufacture of the above tell me. bottled fourteen days or so? Has diaerent temper cause of nectar turning thick and bitty after h anything to do with it, or is it fermentation that cas it? if so, what does the syrup require in it to preve Any information on the above will oblige.-

WATER.

[4528.]-CARVING AND TURNING WOODEN WARE -Can any reader inform me how to make hollow w turnery, such as butter prints, spice boxes, ce? H are they hollowed out, and by what means do they c the screws? They must be done quickly, as they are cheap.-MAP.

[4529.]-CHAIN ADJUSTMENT TO COMPOUND MICROSCOPE.-Would any reader be kind enough. inform me what is the principle of the chain adjustin as applied to the compound microscope, and whether. is sufficiently accurate to take the place of both the ru and fine movements with high powers ?-S.

[4530.] - REMOVING PLASTER FROM GLASS CHANDELIER.-I shall feel obliged if any reader ... inform me how to remove old plaster of Paris fra glass chandalier. I want to take one to pieces, and not know how to proceed.-OXFORD.

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[4532.]-TELESCOPIC, ETC.-Will one of the many readers of your publication inform me whether it would be considered good work for an Sin. reflecting telescope to show Jupiter's second and third satellites fifty-eight minutes after sunrise, the sky being entirely free from

cloud?-H. A. C.

[4583.]-FURNACE FOR HEATING MOULDS.-I understand there is in use in the forges in Staffordshire a patent furnace for heating the moulds from which spades and shovels, &c., are manufactured. The furnace is small, of an oblong construction, and has apertures on each side sufficiently large to admit one or two moulds. The end directly opposite the blast is left open, and acts as vent hole and feeder, into or through which the fuel is passed. Can any reader furnish me with particulars of the construction of this furnace, or give me rny idea who is the patentee-i..., if the thing is really patented?

-W. Scorr.

[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 the grinding, polishing, and parabolizing of planoconvex lenses of 4in. or 5in. in diameter? If large lenses (plano-convex) could be parabolized by his machine, could not a large and cheap object-glass be constructed with facility? I presume that a couple of large lenses both plano-convex, one flint, and the other crown glass, parabolized, would be a cure for spherical and chromatic aberration? Could the lenses be tested in the same manner as his specula ?-RAYMOND.

[4535.]-HORTICULTURAL.-Can any one give me a few instructions concerning pruning gooseberry and currant bushes ?-G. H.

[4536.]-MELTING POINT.-What melting point should I get when I mix paraffines having melting points of 128 and 109 in the proportions of 2 to 1, 3 to 1, and 4 to 1 respectively? Correct answers and how it is done will oblige. Is there a latent heat to be taken into account ?-MELTING POINT.

[4537.1-EQUIVALENTS.-Would Mr. G. E. Davis or any of your chemical subscribers kindly favour me with a list of the elementary substances with their equivalents, according to the new notation ?-MaO Co?.

Can

[4588.]-HARMONIUM PAN.-I have an harmonium and I have spoiled the pan experimenting with it. 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 they would oblige I should be thankful.-W. A. S.

[4539.1-CHIMNEY.-The firm whose engines, shafting, and machinery are under my charge are about to build a new chimney, and I shall be much obliged if you or any of your correspondents will give me the best proportions for it, especially as regards height and size of flue. There are four Galloway boilers to be attached to the chimney, each 24ft. by 7ft. diameter, with 24 Galloway tubes in each; there is also an economizer between the boilers and the foot of the proposed chimney. The works are situated in a valley with hills all around. -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 are any drawbacks to a system of mounting the prism or plane mirror in reflecting telescopes shown in the enclosed sketch. The speculum

[4547.]-A FIELD OF BARLEY GROWN FROM OATS.-Can any correspondent throw any light on the following, which I extract from Elihu Burrit's "Walk from London to John o' Groats "?-"It was a large field of barley grown from oats. The barley sown in this field was the first-born offspring of oats. The head and berry the whole process by which this wonderful transformawere barley, and the stalk and sheaves were oats; and tion is wrought is simply this and nothing more:-The oats are sown about the last week in June, and before coming into ear they are cut down within 14in. 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. This 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 of 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 Bruntisham, near St. Ives, Huntingdonshire, who will supply any additional information needed."-S. G.

is slightly inclined, as in Herschell's, and the image is received on a reflecting prism placed at the side, the prism being a portion of the eye-piece. 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 like to know the opinion of some one of your able writers.-A. WHITE

[4541.]-EMBROIDERING MACHINE.-Can any of your readers tell me upon what kind of a machine the embroidered insertion for ladies' white petticoats is executed? The sewing material is woollen, and the stitch a cha somewhat similar to the Willcox and Gibbs' stitch. I have tried to embroider on the Willcox and Gibbs, but I find it very difficult to make a sharp curve, owing to the great length of the feed. Is there any other chain-stitch machine better adapted for the purpose? I fancy there is. A reply would greatly oblige.-A. BRAIDER,

[4542.]-STEAM PUNCHING PRESS.-Will any of your readers show me how to set steam power to work a vertical screw press, i.e., a press of the kind used for cutting out steel pens by hand, bat on a much larger scale? I want 50 blows per minute. An excentric motion, as in the common punching machines, will not do. Toothed wheels will not do. The motion must be continuous, as the work is too heavy and has to be too quickly done to allow of a reversing action.-PUNCH. [4543.]-TORTOISE-SHELL COMBS.- Could any render tell me how to join tortoise-shell combs?-HAIR

DRESSER.

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[4548.]-IMMERSION LENSES.-What are the principle advantages of the immersion objectives? Do they cost much ?-M. J. C.

[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 the temperature of the water is raised 10 or 12 above boiling point.-SABBAS.

[4550.] -THE SMEE AND BICHROMATE BATTERIES.-I am disappointed with "Sigma's" answer to my query (4450), and after procuring the numbers he this week recommends, find myself very little wiser. At page 341, "Sigma" describes the double cell bichromate battery, and says, "Its use in a simple cell system will be referred to afterwards," which has not been the case for this week at page 482, he says, "But I have now dealt with all the forms I can remember of any general interest and practical value, and therefore conclude this part of the subject." "Sigma'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 100 to tell what it was like, and I am sure, from the description, no one could make one. Will any other of your readers answer my query, No. 4450 ?M.R,C.S. (a New Subscriber.)

[4544.]-PHOTOGRAPHIC. Can a photographer give or sell cartes-de-visite of persons he 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. 278, and also any suggestion he may have to make respecting secret codes?-ARGUS.

[4546.]-DIVISION PLATE, &c.-Will "J. K. P." kindly give the best 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 up a back-geared headstock having two steel cones running in steel conical collars (both to be hardened and ground to a fit)? I also want to know the best angle for the cones; 35° appears to me too great ?-BIERLALA.

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[4551.] TRANSFERRING
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.

is 32ft. 6in. long, 6ft. 6in. diameter, two tubes running through it, each 2ft. diameter.-THOS. DAVIES.

[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 paint, 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 mode 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 other precautions for preserving them besides that of keeping them from the air?-R. E. G.

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

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GILES.

ROMA

No2

[4553.]-SILVERING CLOCK DIALS.-Would "A Morayshire Man," or some other correspondent, tell me why I, as well as "Poor Clock Jobber," cannot silver a brass plate 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 showing all up the centre. So I accordingly set to work and carried out "A Morayshire Man's" directions to the letter, and, send sketches if you can afford space for their insertion?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 off all the old silver, and began afresh-but all to no purpose; for after I had been rubbing the 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 they looked quite black. How is the plate fixed whilst silvering? I lay mine on a clean bit of rag ?-YOUNG COUNTRY WATCHMAKER.

Why,

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

[4555.]-PHOTOGRAPHY.-Will some of our readers

kindly give the 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

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

[4557.]-WOOD ENGRAVING.-I have cut out a
large steamer for a billhead, but had the sea too coarse
and open. Could any one inform me of a composition
(if there is such a thing) with which I can fill up the
hollows, and re-engrave, or must I have the piece cut off
and reversed, and engrave again?-Mus.

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

[4559.]-HORSE POWER.-Please inform me the horse power of my boiler; it is working at 401b. per inch. It

[4565.] INDUCTORIUM'S COIL. -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 umbrella 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 steel leaves used in making the joints of mathematical drawing instruments? I believe they are soldered or brazed in, but am ignorant of the process, and wish to replace some of my present set which have been lost.-S. STEVENS.

[4568.]-WEIGHT OF RAILS.-Can any fellow subscriber oblige me with a rule to find the weight per yard of rails of various sections (iron or steel), whether Tees, Double heads, 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 in our 'ometer. To preserve this we filled the pipes with water, so that nothing could possibly escape 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 any 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 can 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,

cannot take the old one unless it exceeds the above weight. Is such really the absurd wording of the law, or have the wise heads of our officious local police misconstrued the meaning and intention of the Act? Any information on the subject will be very acceptable to many in the trade, but more particularly to-IRONMONGER.

[4571.] RUBBINGS.-Is there any better way of taking rubbings of coins than by using the heelball sold by shoemakers.-W. J. EGGLESTON.

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4157 Reed Organ, 358.

4161 Refrigerator, 358.

4162 Strengthening Steel Wire, 358.

4164 Slits in Steel Gauges, 358.

4170 Smoke Burning, 858.

4172 Boring Bar, 358.

4179 Crayon Drawings, 358.

4184 Lathe Work, 359.

4186 Sheathing Iron Ships with Copper, 859.

4187 and 4258 Steam Carriages. To G. Prew, 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, 359.

4203 Paris, 882.

4205 Naval Architecture, 382.1192

4207 Black Diamonds for Drilling, 382.

4208 Adulteration, 382.

4209 Water-wheel, 382.

4210 Sign Writing 382.

4217 Harmonium Reeds, 382.

4222 Photography, 382.

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EMPLOYMENT COLUMN.

We have frequently been asked to 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 want 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 ENGLISH 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 want it,

OUR EMPLOYMENT COLUMN.

As in the Sixpenny Sale Column, the charge will be sixpence for the first sixteen words, and sixpence for every additional eight words.

The following are the initials, &c., of letters to hand up to Tuesday morning, August 16, and unacknowledged, elsewhere:

C. B. A., C. S., G. H. R., H. S., W. K., Thos. Hirons, W. L., Robert Mastone, Map, R. S. N., S. O'Connel, J. H., Samuel Cracknell, J. O'Connor, J. H., F. W. Grierson, R. C. Browne, Jun., M. & Co., J: C. Hudson, R. R. Antrim, J. W. B., Rev. H. D., German Reed, Rev. E. K., C. D. A., R. Cunliffe, E. West, J. A. Lee, J. H. Collins, R. N., W. Seltar, Terrun, J. H. Wheatley, Rev. Dr. T., Jas. Franklin, S. Brors., J. G. B., B. J. W., P. H. F., J. H. W., J. Hinton, H. Ledger, Horace Jones, Scapegrace, J. H. Long, W. Piper, J. R. F., Amateur Tuner, R. W. B., Andes, W. Willis, W. B. H., J. M. W., All's Well that Ends Well, J.

(Continued from page 408.)

R. F., W. & S., S. O., T. W. W., W. E. Maverly, CONGRATULATIONS & TESTIMONIES.
Thinker, John Bell, Beacon Luff, J. H. B., Sergiurs,
J. H. P., J. H., T. E. Graham, Geo. 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
of Science, J. T., A Poor Mechanic, W. Airey,
Vertumnus, Student, J. H. T., Revd. J. H., An En

graver.

B. E. LODDY AND YOUNG JOBBER.-"Second's Practical Watchmaker," in a letter, says: "I shall be pleased occasionally to reply to such queries as may be in my power to answer."

H. POCKLINGTON.-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 see that we are to have some information on 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., DEWSBURY, 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.

KENSINGTONIAN.-The pump, or its connection with the well, must be out of order.

M. J. WHEATLEY.-Mr. Baskerville's letter on link motion was in type before yours came. VELOCIPEDE.-We don't see how 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 confreres. HENRY MUNRO.-Your answer to "Sabbas " as to a good microscope is an 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 been asked so 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 thank Mr. Pocklington for his kind and courteous reply (183), and also for his promised information on How to Choose and How to Work the

Microscope, which I have no doubt will be highly appreciated by many an amateur reader."

S. A. R.-See back numbers. A description and illustration of the Mitrailleuse are given in this number. W. HARROLD.-Evidently the hall mark. PATTERN MAKER.-There is no quick method of learning to read and work from mechanical drawings. Practice and attention will alone help you. TOMETER.-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 manufacturers 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. S.-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 ex-
cellent bird for the table, although rather out of

fashion.

SPERO. See reply 4433.

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, &c., 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 6d. per gallon. ONE OF THE FIRM OF B.-We do not remember your former letter. should have repeated your your question.

You

T. W. WEDLAKE.-We can give no other information than appears in the article.

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94 "The whole forms a most valuable and instre publication for all who delight in science."-Mar.. Newspaper.

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97

"Your journal, with its moderate pas aud excellent information, is a great boon to the pH. N. HUMPHREYS, Gas Works, New Barat.

98 "The best and most useful journal ever read”T. O'BRIEN, North Wall, Dublin.

99 "Nearly all the members of the VDE, ARtronomical Society are readers of your ele journal."-WILLIAM F. DENNING, Hon. Set, g Astronomical Society, Ashley-road,Bristol.

100 The Rev. Dr. GIBBES, Plymouth, in a letters Editor, says he weekly eagerly expects, became a reads with great satisfaction, the ENGLISH MECHAR 101 "While I am writing, I cannot forbear say word as to the wonderful improvement of the Essus MECHANIC. You must be satiated with congratulation on this subject, but we subscribers must congratulate ourselves. Your latest incorporation will render it a ditionally valuable and interesting. I have often been struck, in comparing the quality of the questions and contributions, with the immense progress they have made since I first became a subscriber-soon after its commencement. This is at least as noticeable in astronomical and cognate subjects as in any other branch of science which has been treated of. I am sure this flows mainly from the educational power of the MECHANIC. The influx of such names as Proctor, Webb, Lockyer, Birt, &c.-not to forget all the other learned though anonymous contributors-has given your editorship the character of quite an era in the history, and a warrant for additional success, of your estimable journal"—I. H. BUFFHAM, Earith, Hunts, July 12.

102" Within less than four months you have term nated the individual career of three publications by sorbing them into yourself. I have had some exper of journalism, but I never saw a speedier and deplet change for the better than has been exhibit the ENGLISH MECHANIC. You have enlarged yr end improved your type; you give better paper and improved engravings; you have multiplied your respondents, as you have certainly widened the scope and purpose of your journal."-SUBURBAN.

103 "I hail the arrival of your most comprehen journal as one of the greatest pleasures of the week, must add my testimony to the zeal and ability va which it is conducted."-H. D. CROZIER, Captain, Baga Engineers, Gibraltar.

104"Quite a mine of intellectual wealth. What & satisfaction it must be to your numerous scientific come spondents to act on the give-and-ta ke principle, and se assist each other in substan ial improvement.”—J. D. SEYMOUR, Albion, Broadstairs.

105 "The absorption of Scientific Opinion and the British and Foreign Mechanic must have increased you already vast circulation, and proportionately augmente your influence in the country."-JAS. HARRIS, Garlinge, near Margate.

106 "The great and increasing success of the Ess LISH MECHANIC, which has grown from an acorn to as oak tree, is the best guarantee that scientific instructica is making rapid progress in the country. For years pas we have had widely circulated and extensively read newspapers and religious publications; now we have az ably edited, many sided, and numerously read scientif journal."-A NEW SUBSCRIBER.

107 "It is as engrossing as a romance to the lover e practical engineering. It is half full of pictures of me chanical and scientific apparatus, and the other half is a concentration of scientific knowledge."-Illustrated MidLind News.

108 "Its chief charm is that its subscribers are mernbers of a universal instruction society."-THOS. WELLS 109 "There is something in it for the engineer, the chemist, the microscopist, the electrician, the lover of natural history, the astronomer; in fact, for the student of all branches of science.-SAMUEL JONES.

The English Mechanic

AND

MIRROR OF SCIENCE AND ART. picture, which was of course drawn with an in

FRIDAY, AUGUST 26, 1870.

SATURN.

BY A FELLOW OF THE ROYAL ASTRONOMICAL
SOCIETY.

planet, only some 16° above the horizon when on the 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 verting 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 (Continued from page 506.) THE HE ellipticity of the disc of the planet itself, night when our drawing was made was of a brightish slate colour. Its tint is not, however; as in the case of that of Jupiter, strikes always uniform-nay, it sometimes varies in the the eye the moment it is applied to the telescope. two ansæ. It will strike the observer, when he On April 19, and later, in May, 1805, Sir William has once fairly got this very wonderful object in Herschel, examining Saturn with reflecting tele-view, how much too narrow the portion of it scopes of various apertures and focal lengths, which crosses the ball appears in comparison thought that it presented a figure "somewhat like with those parts of it in the ansæ. None of the a parallelogram, with the four corners rounded engravings with which we are familiar give this off deeply, but not so much as to bring it to a curious effect. In all which we have seen the spheroid" and that very eccentric writer, but dark ring is represented as far too broad where it assiduous star-gazer, the late Dr. Kitchener, in crosses the globe of Saturn, and proportionally too his singular omnium gatherum on "The Telenarrow in the ans. Returning, however, to our scope," states that he witnessed something of own sketch, the marked ellipticity of the globe the same appearance in September, 1818, with a will be palpable to the student. He will also 3-6in. achromatic of 46in., and a 4in. achromatic notice the bright equatorial belt, succeeded by a of 10ft. focus. The most elaborate micrometrical narrow dark one; that again by a narrow bright measurements, however, made by Bessel in 1833, one, north of which a dusky capping extends and repeated by the present Radcliffe observer, right up to the pole. The shape of the shadow on the Rev. R. Main, F.R.S., at the Royal Obser- the ring B will be remarked too, and the fact of vatory, in 1848, go to show that this effect is its terminating in, or becoming indistinguishable probably referable to some optical illusion, and from, Ball's division. 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-diameter x927. 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 some 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 these "belts," Herschel at first fixed the time of Saturn's rotation at 10h. 16m. 0-4s., and afterwards at 10h. 29m. 16-8s.; Schröter gave a longer period, but the exact one must be considered as still sub judice. 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 shadow 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.

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The subjoined view, drawn expressly for this essay, ad naturam, represents Saturn as he appeared in a 4in. achromatic telescope, with a power of 250, on the night of June 21, 1870, at 10h. 45m. Greenwich mean time, and will serve to illus

trate 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

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., or 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 a 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 Huygnens, 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 astronomer 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 Cyclopædia," 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 Japetus. We append some details with regard to these satellites in a tabular form.

Number and
Name

1 Mimas

Rhea

apparently travels to a considerable distance from
Saturn, and whose orbit, unlike that of the other
satellites, is inclined perceptibly to the plane of the
ring, may also be readily seen; at all events, when it
is situated to the west of the planet.
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 re-
sembling 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 3 aperture; while Mr. Banks
actually saw it easily with a 24in. object-glass.
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.

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Having thus detailed the principal appearances presented by this grand system, we may very shortly endeavour to decipher their significance, and to it we can 2nd any plausible theory to acat for them. And, the outset, we have ever opened a book treating of 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 most 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 a 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

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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 span the Straits of Dover by a single arch of any conceivable material. What then must be the constitution of the stupendous circles of light of which we are speaking? Whatever it may be, it was shown by La Place, in his Theory 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 by 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 Sidereal Revolu- Distance from Saturn the present century,-a work by which its author,

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tion

in his Radii

2 Enceladus

3 Tethys

d. h. m. 8.
0 22 37 27-9
1
6.7
8 53
1 21 18 257

4 Dione

2 17 41 8.9

5 Rhea

4 12 25 10-8

3.3607 4.3125 5.3396 6.8398 9.5528

15 22 41 25-2

22.1450

[blocks in formation]

6 Titan
7 Hyperion
8 Japetus

7 54 40-4

The smallest optical power, as we have intifact, very seldom) the present position of the mated, will suffice to show Titan. Japetus, who

previously absolutely unknown beyond the walls of his own university, acquired, per saltum, a European reputation,-we mean, of course, "Saturn and its System," by Mr. R. A. Proctor, B.A., F.R.A.S., &c., 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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