as metal, glass, china, ivory, bone, &c., at a low heat, say 170; what would be the expansion per 2in. ? 2. Is there any fusible metal that will melt at 170 or thereabouts, and its composition ? 3. Is it known with what power mercury expands? Any answers will be thankfully received.-A. B. C. interesting to metallurgists and chemists, that in the process of stereotyping a forme of types overheated shrinks considerably in height (from face to foot), but remains unaltered in every other respect, so far as can be observed without exact scientific analysis. The metal is apparently as hard, the face is as even and as sharp, and the body is as rectangular and correct as it was before the accident; but the type is spoilt for printing purposes, as it is too low to take an impression when used with other type. I shall be very glad if any of your readers will kindly explain the phenomenon.-sists, or refer me to any work in which I might find such TYPO. [5312.)-SCREW-CUTTING LATHE.-Will' our kind correspondent " J. K. P." inform me the proper distance from the centre of mandrel to the centre of leading screw of a 7in. screw-cutting lathe, as I am altering my lathe to make it screw cutting, but don't know the distance to put up my bracket to carry the leading screw?-IGNORANT. [5313.]-POWER OF ENGINE.-Would any reader let me know through the medium of your journal, the pressure necessary to drive a 14 h.-p. high pressure engine to work at its nominal power, and how many revolutions per minute should it go?-J. B. [5326.]-THE BIRD AND THE BAT.-Will any of your readers kindly inform me of the mechanical principles involved in the flight of the bird and the bat, and also wherein the difference between the two modes con information?-T. R. [5327.]-ASSAYING COPPER ORE.-Will any reader of the ENGLISH MECHANIC be so kind as to inform me what spirits and what quantity of spirits are required for assaying the percentage of copper ores, i.e., after breaking the stone (orey stone), from different copper lodes, and dressing or cleaning for market. I wish to know what quantity of copper it contains. By so doing they will greatly oblige-A FOREIGNER. [5328.]-KNEE-CAPS.-Can any fellow subscriber inform me what is the best material for making kneecaps? something strong and durable, and also waterproof.-D. GARDNER. chuck to hold a cylinder, lin. in diameter, by lin. in depth, so as to turn it, not on the flat, but the round edge? If it could be done, I should like one to divide the piece of metal so as to turn two or three flats on it. I wish to have the simplest, as I want to make it myself.-GE. Ss. [5314.]-BINOCULAR MICROSCOPE.-Will "H. P." [5329.]-CHUCK FOR CYLINDER.-Would any of kindly give a sketch of the mode of mounting the prism"our" correspondents tell me of the simplest and firmest on Mr. Wenham's plan; also the fine adjustment for the objective of same? I am going to fit it up myself. I thank H. P." for his notice of my query.-HYDATID. [5815.]-OLD MEDICAL COIL.-Some time ago I received from a medical practitioner an old medical coil, which was minus the contact-breaker. It is of the vertical shape, and the contact-breaker is affixed to two binding screws on the top of the coil, the core acting as the magnet. Isoon supplied the defect and had it working, but find with one pint cell of Smee's it gives but faint shocks. The power, I find, is regulated by different lengths of the coil brought out and attached to binding screws, of which there are fourteen besides the two for battery connections, which are both marked +. The manner in which the different wires from the coil are connected to the binding screws underneath the baseboard, entirely puzzles me, and I herewith send a sketch of the same, and will thank "Sigma," or any other of your numerous correspondents conversant with the subject, to give me an idea of the rationale of the current. B The wires marked A B and C appear from the thickness to be part of the primary coil; and the others which are of much smaller gauge, the secondary B and C. are connected to the binding screws +. The other binding screws are marked from 1 to 14, the wire A being soldered to No. 14, and the wire C at its other end to No. 1. The outside circle of dots represent the binding screws, the inside circle the I am also holes through which the wires are passed. at a loss to know to which of the binding screws I should attach the wires with the handles, whether one of them should be placed in No. 1 and kept there, and the other wire shifted from No. 2 to 3, and so on, according to the strength required? and what sort of battery would be most effective and economical to use?-EcosSE. [5316.]-SULPHATE OF LEAD BATTERY.-Many thanks to " Sigma " for his answer to my query, No.5015, but if he will oblige, I should like further information concerning the manufacture of sulphate of lead. He says, any soluble salt of lead is precipitated by sulphuric acid. Does he mean that the salt of lead should be dissolved in water, and then sulphuric added until a precipitate ceases to fall to the bottom? And is this precipitate the required sulphate of lead? And how is it dried from the solution? If "Sigma" will clearly answer this, I shall feel greatly indebted to him.INDICATOR. (5817.)-LACQUERS.-Will some obliging reader who is acquainted with lacquering give me the recipes for making a good gold lacquer, a good green lacquer for bronzing, and a pale colourless lacquer?-INDICATOR. [5318.]-SILVERING CHEAP LOOKING GLASSES. -Can any of our readers tell me the way to silver cheap looking-glasses; also the materials required, and method of using? Having some pieces of glass that I want silvered for a particular purpose, I should like to try and do it myself.-A. M. [5319.]-CHEMICAL AND BREWING.-The water I ase for brewing contains a large quantity of iron. How can I get rid of this iron in the water? It prevents the beer getting bright. Would a filter of animal charcoal, vegetable charcoal, and gypsum do? I want some sort of filter which will extract the iron without damaging the water in other respects.-BREWER. Would -CONTACT-BREAKER. "Induc[3820.] torium " say what sort of a contact-breaker he uses? 2nd. What is the weight of the primary wire and secondary? 3rd. Would any hard wood do as well as ebonite? Do both ends of his primary come out at one end of the core of the coil? Perhaps "Inductorium" will be so kind as to send a sketch of his coil mounted, the same as "Sigma" did with his medical coil, as I am sure it will be very acceptable to other readers as well as myself.-J. F. R. [5321.] DRESSING MILLSTONES WITH DIAMOND OR "BORT."-Are there any British manufacturers of Leshot's or any other patent diamondpointed drills ?-M. [5330.]-WHITE LIGHT.-I am greatly in need of an artificial white light, one by which I can distinguish shades of colour; not required to be intense, but regular, Is there any and moderate in cost first and second. plan of taking the yellow out of gas or any other artificial light? I have tried tinted glasses for correction, but they do not answer.-J. O. R. [5331.] - CONTRACTION AND EXPANSION OF METALS.-If iron be heated and plunged into cold water it becomes hard and contracts, but if copper be heated and plunged into cold water it becomes soft. How is this accounted for? It seems a contradiction of the general law, viz., that all bodies expand by heat and contract by cold.-A CONSTANT SUBSCRIBER. [5332.]-DRY ROT IN WOOD.-Any reader will much oblige by informing me and your subscribers the best plan to prevent dry rot in wood floors. We have had a new floor of the best red deal laid in a new building about four years since, the earth being about 4in. below the wood, and it was so bad in two years it had to be taken up and replaced with an entire new floor. It is only eighteen months since the last floor was put down, and it is going again very fast, and will have to be removed very soon.-YORKSHIRE. [5333.]-POULTRY KEEPING.-Will some kind cor respondent oblige me with particulars for keeping poultry? I want to know what profit I could expect per score hens, and the best way to dispose of the eggs and chicks? I have bought a "Manual for the Many," but it does not give the profits that can be made; its instructions are for those that keep them for their own use. I want to make a living if I can.-FEMALE SUB SCRIBER. [5834.]-MODEL ENGINE.-Will some one help me ? I want to try to make a model engine to work. What I want to know is which is the easiest sort to make, horizontal, table, or beam? I also want to know all the sizes of each. I should like to have the cylinder lin. bore. I have no lathe, and if, sir, you would find space for a few illustrated parts, I am sure Mr. Baskerville, or "J. K. P.," or some other clever correspondent, would send the same, which would be a boon to a great many. -W. REED. [5336.]-RUSSIA.-Will some kind reader inform me whether it is necessary that an engineer going to Russia should know the language, and if so, where could I procure a Russian grammar ?-H. N. [5337.)-FILTRATION.-Will some reader describe the process of filtration through which the water goes that supplies London, or any other large town, stating form of sand beds, proportionate thickness, kind of sand and how often renewed or cleansed ?-E. H. J. [5338.)-STEEL BOILERS.-Will any of your correspondents who have had practical experience in the making of steel boilers be kind enough to answer the following questions? Are the plates set cold or heated, holes drilled or punched, price of plate per cwt., and where to be had? Are not steel plates more liable to become brittle than iron ones, after the boiler has been in use for a length of time, making them more difficult to repair? A sketch of a single-tube boiler of the most modern make, mounted with steam dome and showing the ends properly stayed, will oblige; say steel boiler 15ft. long, shell 5ft. 6in. diameter, tube 2ft. 9in., to work at a pressure of 40lb. per square inch, what thickness should the plates be? At the same time, can any brother reader tell me the best practical work on boiler making, where published, and at what price ?-VULCAN. [5339.]-HYDROGEN GAS.-Will any reader inform me in what proportions to mix sulphuric acid and water to make hydrogen from iron ?-JUMBO. [5840.]-ULVERSTON PIG IRON.-Will any friend tell me what are the qualities of charcoal lorn pig iron, [5822.]-WORKING SAW BENCH WITH HORSE.-made at Ulverston, Lancashire, and how it is made, and I should feel obliged if some reader would inform me the class of ores used? I am told it is £10 per ton. how I can work a saw bench with a horse? I have a -LEARNER. horse that is not at work half his time and should be glad if I could use him in that way, not having sufficient work for a steam engine.-A YOUNG BEGINNER. (5323.] RHODIUM.-Can any reader tell me how I can detect the presence of the sodo-chloride, oxide, and phosphuret of this substance ?-Z. [5324)-REMOVING PAINT AND TAR.-How can I remove oil paint and tar from oil-cloths, tarpaulins and other fabrics, so as to obtain the body cloth intact? Can some kind reader oblige?-OLD TAR. [5823.]-EXPANSION OF METALS.-1. Can any render inform me which is the most expansible substance [5341.]-SOAP MAKING.-I shall feel obliged if some of your subscribers will name the best work pub. lished on soap making; also the best mode of bleaching palm oil.-H. J. D. [5342.]-SILVERING SPECULA.-Will Mr. E. M. T. Tydeman kindly explain the tartrate of soda process, alluded to in his letter, No. 453, p. 38 ?-HuGo. [5348.]-DRY COLOURS.-I should feel obliged if some of your subscribers will kindly inform me how to make dry colours, such as greens and blues, &c., or name a work which will give the information; also the best work on varnish making.-H. J. D. [5844.]-SILVERING PROCESS.-I should be obliged if any of your readers would give me the title, price, and publisher of a work, or works, on the patent silvering process (nitrate of silver), and also platinum silvering.J. W. RANDALL. [5346.]-LEAKAGE [5845.]-ILLUMINATING GOLD.-Can any one give me directions for using "Leroux & Son's " (I believe that is the name) illuminating gold and silver fluid, sold in bottles at 1s. and 28. ? I want to use it with either pen or brush.-DRAUGHTSMAN. IN SLATE ROOF.-I have had a leakage in my roof, "a slate one," for the last eight or nine years, and have had several different men in to see to it, and followed their plans as far as I could, including a new gutter, but still the water comes in every time it rains. Can some of my brother readers suggest a remedy for so unpleasant and disheartening an affair? I may as well add that there are no skylights in the roof, nor does the water drop into the attics, but into the cornice in the second floor, at the side of one of the windows.-OWEN GLENDOWER. [5347.]-MODELLING IN CLAY.-Will a "Working Woman," who replied to query 4975, kindly tell me if any book has been published on the art of clay modelling, a practical and not expensive work? Also whether designs for modelling figures can be obtained? I find it difficult to model correctly without something to copy from.-AN UNSUCCESSFUL MODELLER. [5348.]-THE PHANTOM WHEEL.--I have lately heard an opinion expressed by the captain of a bicycle club in London that an ordinary wheel fitted with a "Phantom "rubber tire is equal if not superior to a "Phantom" wheel (with rubber tire) itself. Can any bicycle riding friends endorse this statement ?-MUZZLE LoADER. [5849.]-A COTTON SPINNER'S DIFFICULTY. — Would any of your numerous readers in the cotton district help a brother spinner out of a difficulty? I have to work a double beater scutcher, and the cotton will stick to the last beater blades, and when it gets on to one side takes all the draught from the other, and so causes one part to choke and make a bad lap. Some time ago we had several letters on cotton spinning which contained amongst many words some good practical hints which were valuable. Could you not induce some of your valued correspondents to write again on this subject, for it is scarcely to be credited, that in such a large trade as cotton spinning, there is not a single practical work on the subject? I know there are plenty of books giving instructions as to calculations, but every one who is in the trade knows that to be a very small part of cotton spinning. If any brother reader knows of any work on the subject giving practical hints I should be glad if he would name it. In the mean time could we not help each other through the ENGLISH MECHANIC ?-B. [5350.)-ELECTRO-MAGNET.I have made an electro-magnet of -iron, and covered with No. 18 cottonThe wire gives thirtycovered wire in four layers. six turns to the inch, and the approximate quantity used is about twenty-four yards. As "Sigma," in his valuable paper says the battery used should be proportionate to the resistance, and as I have not the means of measuring the resistance of the wire on the magnet, I will thank your able contributor or any reader to inform me how many cells of the sulphate of lead, manganese, or Daniell's battery would be required to work the I wish to apply it to the lifting magnet effectively. of a weight of 4oz., placed at the distance of fin. from its poles once in every two seconds. Perhaps some of your correspondents would be so kind as to give their opinion as to its capability of performing the work mentioned.-Ecosse. [5351.]-TINNING COPPER.-As I observe from some of your correspondents' answers to queries respecting the sulphate of lead battery that the copper cups forming the negative plate require to be tinned to preserve them from local action, I will be greatly obliged by the information how to tin them. I understand it is done by boiling the article to be tinned in some solution of tin, but that there has lately been an improved method of doing it discovered.-ECOSSE. [5352.]-CLUB WHEAT.-A sort of wheat is called by that name in the United States. Could any brother reader favour me with the explanation of that name?B. C. W. [5357.]-THE POST-OFFICE TELEGRAPH SYSTEM. -Will any brother reader give me instructions through the MECHANIC how to learn the telegraph instrument, as used in the Post-office? By so doing they will oblige, and I think it would benefit my brother readers.-POSTMAN JOE. [5358.]-OIL LAMP FOR MAGIC LANTERN.-Will some kind reader inform me which is the best kind of oil lamp for magic lanterns? There has been a great deal said in back volumes, but nothing about oil lamps. -ZETETIC. [5359.]-TEETH OF WHEELS.-Could any of your readers give a scale and description of the teeth of wheels on the odontograph principle ?-ZETETIC. [5360.]-ENGINEERING ESTABLISHMENTS.-Will some subscriber please state what engineering works employ the largest number of hands, and state the number of hands employed by several of the largest works in the world ?-DRAUGHTSMAN. [5361.]-SELF-ACTING INCLINED PLANE.- Will any reader of the ENGLISH MECHANIC be kind enough to give a rule to ascertain the necessary inclination of a self-acting inclined plane, the loaded waggon to pull up the empty ones? I wish to construct one from a quarry which rises 84ft. in a distance of 1,980ft. Will the present inclination do for that purpose ?-CLECKHEATON. [5362.]-INCLINED PLANES.-TO THE REV. E. KERNAN.-Will the Rev. E. Kernan solve the four problems on inclined planes which appear in page 582, Vol. XI., and oblige one who wishes to learn?-CLECK HEATON. [5363.]-STEEL PLATES.-I want to harden some steel plates, of 15-gauge thickness, and from 4in. by 6in. up to 12in. by 8in. Can any subscriber say what I must do to prevent them from warping, or how to straighten without softening them ?-FRED ROE. [5364.]-CIGAR SHIP.-Will some correspondent tell me what has become of the "cigar ship;" whether it has been out to sea, and if so, in what respects it failed to fulfil expectations?-W. [5365.] ELECTRO-MAGNETIC ENGINE.-Will some brother reader kindly answer my query (No. 5024) ? Surely out of the immense number of correspondents to our MECHANIC some one could give a description of the above which would greatly oblige me ?-INDICATOR. [5866.]-CHURCH BELLS.-Will some one inform me the weight of the three heaviest church bells in Eng. land ?-R. CROOKE. [5367.] - BULLET MOULD.-How is the hollow (called, I believe, the cherry) in a bullet mould, either conical or spherical, made ?-FABER. [5368.]-NUTS FOR MODELS.-How can I make nuts and bolts for screwing up models, the bolts to be about 1-16" diameter, the nuts about 3-16" diameter? -FABER. [5369.]-INSTANTANEOUS PHOTOGRAPHY.-I am a farmer and amateur photographer. I want to take photographs of my cows, horses, sheep, &c. Can I work instantaneous with the bath I am now using; the exposure is about 30 seconds in my glass room?-A FARMER. [5370.]-HOT-AIR v. STEAM ENGINES.-It is said that hot-air engines are theoretically inferior to steam engines, inasmuch as the same amount of heat when applied to evaporate water will produce far greater motive force than when used to expand air. Will some kind reader show me a concise method of making the calculation, and also state what are the practical disadvantages of hot-air engines ?-QUILLDRIVER. [5871.]-VENEZUELA.-Will any of your readers give some information of Venezuela, as a place of emigration?-J. W. R. [5372.]-POWER OF ENGINE.-What would be the power of an engine having a cylinder 4in. by 2in., also of one 4in. by 8in. both working at 75lb. ?-IXION. [5373.]-PLASTER CASTS, ETC.-Will some one of our readers kindly inform me how I can harden moulds made of plaster of Paris, so as to take casts from them, and also the best material (if there is anything better than that recently described) to take moulds of groups of fruit, &c.?-Mus. [5874.]-COUNTERPOINT.-I should feel obliged to any fellow student of counterpoint if he would say whether I can invert (or rather whether it will) a minor canon upon the 5th, resolving all accidentals, and also all leading tones, into the major. Some are capable of being augmented (if I may call it such), and then inverted, but can only be used by the addition and aid of passing notes.-CARL DITTENHOFFER. [5875.]-DEFECTIVE COIL.-Will you allow me to ask some reader to help me out of the following difficulty? I have a six-celled galvanic machine, by Smee, which I use medically, being an invalid. The battery is in good working order, proved by trying a small coil; but my own coil will not work. Several times the handle of the positive director, in front of the coil, touched the negative pole, also in front of the coil, and caused the vibrator to rise with a sort of shock. 1st.Can this have injured the coil; and will any brother suggest what is necessary to remedy the evil? 2nd.-Is it likely to injure a small coil, lin. in diameter, and not over 34in. long, to use all the six cells? I think I have read somewhere that excessive battery power, with a small coil, may destroy the insulation of the coil? 3rd. -When the insulation of the coil is destroyed, what must be done to restore it? 4th.-If a new coil is necessary, is there any one more effective for medical purposes than others; quantity rather than intensity being the thing required?-G. F. L. (5376.] ELEMENTARY VEGETABLE PHYSIOLOGY.-Could anyone kindly point out any work on Elementary Vegetable Physiology to-BOTANIST. [5377.] -TO "INDUCTORIUM."-What weight of P. wire did you use in your coil; what was the cost of the ebonite; have you tried glycerine in place of oil for your pump? It ought to answer well.-OPERATOR. The magnet [5378.)-TO "SIGMA."-Will you kindly tell me if a pound of No. 14 cotton covered, or an equal weight of No. 16 cotton covered copper wire would excite ar electro-magnet lin. diameter, 8in. long, most powerfully, using in each case one or two of Bunsen's pint size; and if two cells would excite more than one? is the core of an induction coil.-OPERATOR. [5379.]-WINE IN A GLASS.-Has any one of your readers observed how almost perpetual is the motion of the film of wine (sherry) on the sides of a wineglass? How long it will continue I do not know; if the glass is covered over certainly for many days. Is it due to adhesion. The glass must be all but emptied.-M. P. [5380.]-LOGARITHMS.-I wish to learn to work arinetic by logarithms. Can any reader tell me of a book, name of publisher, and price, by which I could learn the above?-F. W. S. [5381.-HYDRATED OXIDE OF ANTIMONY.-Will some kind reader be good enough to tell me the way to make the above.-G. J. T. [5882.)-VIRGINIA.-Will any brother reader be kind enough to inform me re the following queries about Virginia ?-What is the quality of the soll near to Washington; and which is the best grain to cultivate so as to be marketable in Washington? What is the length of the summer, and also of the winter, and the degrees of heat and cold to be expected there? Is the river upon which Washington is situate navigable 25 miles up? The price of farm labour about Washington; and if negro labour is obtainable, and the price? Are there good large fish in the river, and are there wild fowl within a radius of 25 miles of Washington? What is the price of land about the above place, and the quality of the timber, and if fit for building purposes, and if easily wrought?-WASHINGTON. [5383.]-GASEOUS VAPOUR.-Can you or any of your readers inform me through the ENGLISH MECHANIC what gaseous vapour is formed when sulphur and nitric acid are heated together? When passed into water and and indicates likewise the presence of nitric acid.-W. tested with chloride of barium, it forms a milky solution, MATON. [5884.1-RESPECTIVE MERITS OF TELESCOPES.has such a decided objection to 8in. O G telescopes in If it be a proper question, may I ask "F.R.A.S." why he general, and of Solomons 3in. telescope in particular? Through almost all his correspendence in the last volume of the ENGLISH MECHANIC he speaks detrimentally of them. In one of his letters he says he would reckon a 3in. O G not only good, but miraculous, that would show 5 stars in the Trapezium of Orion, considering 3.75 the very least aperture which would show the above 5 stars. Now all Solomon's 3in. telescopes are warranted to show 5 stars in the Trapezium of Orion; and the Rev. F. E. Winslow, who has one, says he saw five stars distinctly, highly of the above telescope, and I am sure many of with it. "Scorpio" and "Amateur" also speak very correspondents can support them. Why then does "F.R.A.S." speak of them in a disparaging tone? I have not yet got one myself, but thought of purchasing one. Would "Amateur," or some other of your talented correspondents, give their opinion of the telescope in question, and they would much oblige.-CUMBRIAN. [5385.]-ORGAN ACCORDION.-Can any corresponaccordion, or organatina, with and without the tremolo dent kindly explain the construction of the organ stop? And how is it that beautiful soft tone attained; also size of parts, number of notes, &c., best adapted for a good instrument? A sketch would oblige.-G. W. our your correspondents tell me how the ornament in [5386.]-GLASS MARBLES.-Could you or any of glass marbles is done? I am sure if any one would describe the process it would interest more of your subscribers than-AN ATHENIAN. [5387.]-THE NORTH POLAR STAR.-Thanks to Mr. Birt. Will he kindly further oblige me by stating on and how long will it stay in that position ?-CYRO. which side the Pole Star is 1° 23′ from the North Pole, [5388.)-SIPHON PRESSURE GAUGE.-Would any pressure gauge, as mentioned in the ENGLISH MECHANIC, brother reader kindly inform me how to make the siphon No. 283, August 26th, to indicate up to 201b. ?-A CONSTANT READER. [5389.]-MOULDY BREAD.-I found some bread that had been left in a house, and I observed it to be very mouldy. When I came to examine it under my microscope I found it to be covered with large berries, and it all appeared to be held together by long elastic bands. I wish to know if that is very common, and what kind of a fungus it is, or if it is a fungus at all?H. WHITHAM. globes whose diameters are 14iu., 16in., 18in., and 20in. [5390.]-DIAMETER OF GLOBE.-I have four metal respectively, and they are to be melted down into one globe, and I want to find its diameter. kindly tell me of some rule whereby to ascertain the Will some one diameter. If the weight has anything to do with it I know the weights.-DRYDEN. [5391.] electrical correspondent favour me with titles of recent works on electro-metallurgy, or any of its branches?T. A. U. ELECTRO-METALLURGY. — Will some thank any of my fellow-subscribers to inform me of the [5392.]-CLEANING MEERSCHAUM PIPE.-I will best way to clean or renew a meerschaum pipe which has become oily ?-SMOKER. and block; also how to dye them black and brown? If [5393.]-WHITE FELT HATS.-How to clean, stiffen, any correspondent will kindly answer the above they will greatly oblige.-JOHN THOMA S. [5402.]-KEEPING WALNUTS.-Can any one inform winter ?-Nux ? me of the best way of keeping walnuts for use during the [5403.]-VAL DE TRAVERS ASPHALTE.-I should me of the chemical composition of the asphalte now feel obliged if any correspondent would kindly inform being laid in Cheapside.—R. G. B. Society,' the English Mechanics' Scientific [5404.]-THE EPICYCLOIDS.-Would "Member of and Mechanical or some other mathematical correspondent, give the theory of the epicycloids?-J. W. PASSMAN. [5405.]-A DIFFICULTY.-PULLEYS.-Will any of ing-Two pulleys of, (say) equal diameters, are conyour numerous correspondents assist me in the follownected by an endless band. How can I contrive to make the second pulley rest during every third revolution of the first? In other words, how can I obtain an intermittent motion of the second, from a continuous motion of the first, without introducing a train of wheels between, which is just what I want, if possible, to avoid? I have examined your illustrations of mechanical motions from the beginning, but fail to find anything to answer my purpose.-G. S. [5406.]-BLACKENING INSIDE OF TELESCOPES. -will" A Fellow of the Royal Astronomical Society," 587, col. 1) to Mr. Hill. He there says that it would be be kind enough to refer to an answer given by him (page a telescope tube. I do not for one moment question this; a good plan to blacken with a dead black the inside of but is the reason given the correct one, namely, the less light lost by internal reflection, obviously the more will tubes, one of which is blackened in the inside and the pass through the lens. Now it appears to me that of two other not, that more light will pass through the one falling on the side will be absorbed, but if the sides are not blackened. For if the inside be blackened, the light not blackened some of the light falling on them will be reflected, and some of it will eventually pass out at the light will pass through the tube whose inside is not further end of the tube. Thus it seems to me that more blackened. I do not say that the blackened tube will not be better for astronomical purposes, but merely that more light will pass through the further end of the unblackened one.-SAEPE. [5407.]-SPECTRUM ANALYSIS.-Will any of your kind correspondents give me a list of the spectra given by each and all the elements, if it would not be encroaching on too much of your valuable space ? and oblige-AN OLD DUFFER? [5408.]-AERIAL VOYAGE.-The readers of Scientific Opinion will probably remember that in No. 15, Vol. I., of that journal, it was announced that M. Alex. Chevalier intended to cross the Atlantic Ocean in a balloon, and that he had gone to America for that purpose. Will they, or any other kind reader, inform me whether the attempt was ever made; and, if so, with what result?— WILHELM M. B. me the best kind of varnish for varnishing maps [5409.]-VARNISH FOR MAPS.-Will any friend tell mounted on canvas?-G. L. UNNOTICED QUERIES. IN future, if any query remains unanswered for four weeks, we shall insert the number and subject of the query in this list, where it will remain for two weeks, if not previously replied to. We trust our readers will for the benefit of their fellow-contributors. look over the list, and send what information they can Choo," 4679, 4695, 4722. 4730 [5394.]-REFINING OLD METAL.-Can any of my brother readers favour me with the particulars of the Acklam Refinery, Middlesbro'; with the size of cupola and ores or oxides of iron used? I have to refine a large 4736 quantity of old metal, and want it free from impurities? -SMELTER. 4735 Nail-making Machine, p. 598. Pearl Oyster Shells, 599. Balance in Verge Watches, 599. 4743 Hem-stitching Machine, 599. 4745 Starch, 599. 4747 Glass Burning, 599. 4750 Softening and Purifying Water, 599. 4754 Dressing Skins, 599. 4755 Conical Winding Drums, 599. 4756 Constructing Magic Lanterns, 599. 4762 Displacement of Ships-To W. Felton, 593 4763 Soldering Britannia Metal, 599. 4767 4769 Civil Sevice Examinations, 599. Model Paddle Steamer, 599. 4777 Link Motion, 599, 4778 Dentist's Cement, 599. Tempering Steel Needle Wire, 599. Conveyance of Water, 599. obliged to " Seconds Practical Watchmaker," if he will [5397.]-CONTRACTORS' ESTIMATES.-Will some [5400.]-DISSOLVING VIEW APPLIANCES.-I have oxygen and household gas from main, and can always a set of full-size apparatus, 3in. condensers use show a good picture by transparency-have lately purchased a new aphengoscope, for showing carte de visite light on a spot about the size of a shilling. How can and opaque objects, but can only get a "really" bright I disperse it over the whole picture?-OPTICS. flame is suitable for brazing with the blowpipe, where [5401.]-BRAZING WITH THE BLOWPIPE.-What gas cannot be obtained ?-HOROS. Horizontal Oscillating Cylinder, 622. 4793 Iron Ship, 622. 4801 Greenhouse, 622. 4802 Water Power Wanted, 622. 4803 Faure's Battery, 622. 4809 Celestial Globe, 622. 4814 Water Supply, 622. 4815 Good Reed-Organ Pipe, 622. 4817 Steam Carriages, 622. Rubber Valve, 622. 4820 Ebonizing, 622. 4818 4821 Pendulum Spring, 622. 1827 Motive Power for Lathe, 623. 4836 Artists' Lay Figures, C28. 1839 Cannon, 623. 1841 Sponges, 623. 1818 Hydraulic Apparatus, 623. 1953 Gearing for Bucket, 623. 4857 Model Windmill. To John James, 623. 1860 Regulation of Compass, 623. 1861 Incline, 623. 1867 Australian Nugget, 623. 1868 Trumpet Stop, C23. The English Mechanic AND than the others, whether there is anything in what showers observed when the earth passes through we know about this stream to lead us to suppose the system, is in reality one of the least important that it is more important than the rest. of the meteor-systems. The comet with which it It seems to me abundantly clear that the con- has been (beyond all question) associated is so trary is the case. We have only two means of faint and small that it has never yet been disjudging of the richness and importance of a cerned by the unaided eye. In a powerful telemeteor-system. One is the observation of its scope it appears but as a faint nebulous light, WORLD OF SCIENCE AND ART. apparent richness, and the individual magnitude nor is it even adorned with the ordinary appendage of respectable comets-a tail. Taken apart from the significance of what we know respecting it, this comet is certainly one of the least striking objects which the telescope has ever revealed to astronomers. FRIDAY, NOVEMBER 4, 1870. METEORS AND SHOOTING-STARS. (WITH PARTICULAR REFERENCE TO THE NOVEMBER METEORS.) A In of the meteors belonging to it. But the apparent richness alone can be but a deceptive indication of the real richness of a stream of meteors. If we were sure that the earth plunged through the heart of each meteor-stream, we could indeed learn something in this way, precisely as we On the other hand, the August meteors are asmight compare the relative thicknesses of dif- sociated with a comet of distinction-with a comet ferent cords by the resistance experienced in which has been watched by many millions of piercing them through the middle with a needle. human beings as the harbinger of some uncanny BY RICHARD A. PROCTOR, B.A., F.R.A.S. But we have no assurance whatever that the event, and has been recognized even by men of MONGST the many surprising discoveries earth passes through the heart of a single science as worthy of respectful attention. which have of late years rewarded the meteor-system. It may be that if she did the deed, if its approach had been anticipated and labours of astronomers, none perhaps are more results would not be altogether pleasing or its course known, but the hour of its arrival unremarkable than those which relate to the phe- satisfactory to her inhabitants, and certainly certain, it is far from unlikely that men of science nomena-once thought so insignificant-presented the chances are enormously against her doing so. would have looked forward with some dread to by" falling stars." Ten years ago, though the The minuteness of the space actually passed the possible effects of its arrival. For it was one thoughtful astronomer had become convinced that through by the earth on her course round the sun of those comets-few, indeed, among the larger these objects really belong to the domain of astro--at least the minuteness of this space by com- sort-whose track crosses the earth's; and had nomy, doubt still rested on that theory of their parison with the dimensions of the solar system it come but a few months earlier or later, we should nature. Men could scarcely believe that the vast is not commonly appreciated. If we represent by this time have had the means of answering that depths amidst which the planets pursue their career the sun as a globe about as large as a billiard-long-vexed question whether the earth would suffer around the sun are the home of countless bodies ball, the space along which the earth pursues her injury were she to come into direct collision with a which rush with even more than planetary velocity course must be represented by a thread or wire large comet. So that if we judged of the relative upon wide orbits round the solar orb. It seemed finer by far than a hair, and forming a circle a importance of the August and November meteorincredible that each of those faintly gleaming hundred yards or so in diameter. Now, conceiving systems by a reference to the relative importance lights, passing with silent swoop across a star- such a circle, and regarding the meteor-systems of their comet companions, we should undoubtedly group-leaving no trace of their existence and as oval hoops round the central ball which conclude that the August [meteors are far the seemingly as little important in the economy of happen to cross this fine circular thread, it is most important. It would follow from this that nature as a rain-drop or a snow-flake-indicates scarcely conceivable that in one case out of a since the November meteor-system produces the close of a career during which the mighty thousand the thread would pass centrally through showers quite as striking as any seen in orbits of Jupiter and Saturn have been encircled, the substance of one of the hoops. August, we do not in reality see the full splendour nay, often the utmost limits of the known planeof the August meteors-but passing only through tary scheme overpassed by uncounted millions of its edge, recognize but the scattered outliers of miles. the system. Even now, when the nature of these objects has been revealed to us, and some insight afforded us into the part which they perform in the economy of nature, it seems difficult to realize the full significance of ascertained facts. The very aspect of the planetary scheme seems changed as we contemplate the results of recent labours in meteoric astronomy. Kepler and Copernicus, could they revisit this world, and, mixing as of old among astronomers, inform themselves respecting the theories now upheld, would scarcely recognize the scheme of the universe so unfolded to their view. Truly the harmony of the planetary system recognized by Kepler seems strangely marred, "as sweet bells jangled out of tune and harsh," by these eccentric meteor orbits. These crowds of independent orbs rushing disorderly around the sun in no sort resemble the "obedient family" which Copernicus recognized in the solar system. Many times during the last few years the history of those discoveries and researches by which meteoric astronomy has reached its present position has been recounted. It is not my purpose to describe these matters anew. But it has seemed to me that the approach of the earth towards that great stream of meteors to which the November shower is due, will render a brief discussion of some of the most striking facts lately discovered not unacceptable even to many who look on astronomy from afar off, and regard astronomers somewhat as Indians regard their medicine-men. We, therefore, can infer little or nothing from the apparent richness of meteor-streams as to their real importance, because we do not know whether our earth passes through the core of any particular stream or merely grazes its surface. We may learn something from the average dimensions of the meteors belonging to a system, though our inferences may not be altogether reliable. So far as this point is concerned, the November meteors would seem relatively inferior to many others. They are too small to penetrate through the atmosphere, so as to reach the surface of the earth, not one instance being on record of a November meteor affording any tangible evidence of its existence; and from the researches of Professor Alexander Herschel it would seem that on the average the November meteors weigh but a few grains each. When we compare this with the fact that bodies belonging to other systems have been found to weigh many pounds, some even being several tons in weight, the relative insignificance of the November system in this respect will be recognized. But there is a second method by which in comparatively recent times it has become possible to guess at the importance of different meteor systems. The surprising discovery that many meteorsystems are associated with comets has not hitherto been fully interpreted. We know quite certainly that along the orbits of certain comets there travel myriads of tiny bodies-meteorswhich we assume to be solid. But what connection there may be between the gaseous comet and its solid attendants, whether the comet gave birth to the meteors, or whether the meteors in some way or other combined along one part of the system, to form the comet, has not hitherto been explained. It may be regarded indeed as one of the most mysterious facts ever discovered by astronomers that any association whatever should exist between bodies seemingly so different in their nature as comets and meteors. But there the relation is, let us make of it what we will. No doubt rests on the validity of the discovery; no one who understands the nature of the evidence can believe for a moment that the relationship is merely apparent, and the coincidence of orbits merely accidental. So that, in fact, it has come to be gravely questioned whether any meteor system exists without a cometic nucleus, and whether any comet exists without a meteoric We may take the November shooting-stars as typical of a class of meteor-systems, which must undoubtedly be very numerous. It is true that as the earth sweeps on her wide orbit round the sun she encounters few such streams as that to which the November meteors belong. As she reaches certain critical parts of that orbit she is exposed, indeed, year after year, to a species of cannonade of greater or less intensity; and occasionally the weight of metal with which she is thus assaulted is far heavier than any which she has to encounter during the second week in November. But for a systematic and continuous downpour of missiles the November stream is unsurpassed by any, except perhaps the August meteor system. If we could count the total number of meteors which have been rained upon train. the earth during the past five or six centuries. and assign each individual meteor to its proper system, I have very little doubt that the November stream would be found to have supplied a full tenth part, though the total number of systems which our earth encounters is known to exceed one hundred. This being the case, it may be worth inquiring whether the November system is in reality richer Be this, however, as it may, we are at least justified in comparing together such meteorsystems as are known to be associated with comets, and inferring the probable importance of such meteor-systems from the observed brilliancy of their comet-chief. But this being so, those who remember the magnificent display of November meteors in 1866, will consider with amazement how grand the August system must be if it is really capable of supplying a far more splendid shower. We remember how the stars seemed to fall continuously, so that at every instant (at least during a certain interval) shooting stars could be seen in some part or other of the heavens. And we know, also, from the accounts of Humboldt and Bonpland that, sixty years before, there had been a yet grander display. If a meteor-system associated with so insignificant a comet as that of 1866 can produce these wonderful showers, how inconceivably magnificent would be the scene if the earth passed through the heart of the August meteor-system, associated as that system is with a comet of considerable splendour! But similar considerations may fairly be extended to all the meteor-systems which the earth encounters. These are counted by the hundred, and though most of them seem insignificant compared with the August and November systems, yet we have seen that no opinion can hence be formed of their real importance. Some of the m may as far exceed the August system in importance as that system probably exceeds the November system. Nay, we have two excellent reasons for feeling some degree of assurance in this respect; for one of these less-noted systems has been associated with the comet of 1861,-an object not inferior in splendour to Donati's comet-and some of the recognized systems occasionally send us visitors in the form of massive aerolites, compared with which the tiny bodies forming the August and November meteors are as small shot to the Whitworth bolts. Startling however, as are the considerations thus suggested, it is when we pass in imagination beyond the confines of the earth's orbit, that the true significance of what we know respecting meteors and meteor-systems becomes apparent. We have seen that our earth really visits but a minute proportion of the solar domain. The space actually traversed by our globe as it circuits round the sun, though enormous compared with any of our ordinary estimates of size-nay, though exceeding fifty-fold the volume of the sun-is yet but the minutest fraction of that vast sphere over which the sun exerts supreme sway. Now sine the meteors are not individually discernible sive when they enter the earth's atmosphere, all our direct information respecting the condition of the interplanetary spaces is derived from the actual contact of the earth with Now, judging in this way, we should be led to bodies belonging to thos spices. We obtain our conclude that the November stream, notwith-information respecting the planets through their standing the wonderful magniicence of the star-visibility, but as respects the meteors our earth [5198.]-THE MONT CENIS TUNNEL.-Professor Ansted contributes an article to the current number of the Popular Science Review on "the Geology of the Mont Cenis Tunnel." The following are the rocks met with in the tunnel (commencing with the north or French entrance), as indentified by Professor Sismonda:-1. Upper member: consisting of schists, sandstones, and psammite with anthracite, resting on a thick band of quartzite, corresponding to Oxford clay series, 4,500 ft. thick. 2. Middle member: gypsums, crystalline, limestone, and calcareous schist, corresponding to Lower Oolites, 1,700ft. thick. 3. Lower member: calcareous schist, with bands and strings of quartz and threads of limestone; Liassic and Rhetic series; 17,500ft., thick.J. FORD. ["Beacon Lough" also answers this query from the same source.] [5231.]-GROVE'S BATTERY.-If during the time the battery is not working, though charged with acids, a hissing sound is heard, the zinc requires reamalgamating, how often depends on the amount of work the battery has and the quality of the porous cellOPERATOR. [5235.]-COLOURING CHEAP TIN TOYS.-They are coloured or gilded by painting them over with deep gold lacquer, sold at any brassfounder's. A little practice will be all that is required to obtain good results. The brighter the tin, the better they look when finished. -GE. SS. [5236.] VOLTAIC PILE. - A dry pile, first constructed by Lamboui is composed of sheets of paper, gilt or silvered on one side, and coated on the other, with peroxide of manganese and gum water, these are pressed into a glass tube alternately, each metallic facing meet[5203.]-BRAZING SHEET STEEL.-File the lapsing a manganese coating. Even when the alternations on a bevel, so that they lap thus, and then lay half-dozen amount to thousands the quantity of electricity is exlengths of brass wire for brazing in be- tremely feeble.-TRINITROPHENIC tween, and on the laps; bind all round with I common binding wire; lay on borax on laps, wet the borax and direct blast until the brass flows; let cool and clean off with file.-W. REED. [5203.]-BRAZING SHEET STEEL.-" Tit for Tat" must turn his steel up in the form that he requires; clean the seam, then anoint it with borax and water, then lay on bits of clean sheet brass and braze with blow pipe on hearth. The steel should be tied up with wire to keep the seam close.-J. MOSELEY. [5208.]-PRACTICAL GEOMETRY. The following will be found useful:-"Elements of Descriptive Geometery," by J. Woolley, text, 8vo., plates, 4to., published by Parker, London. "Practical Geometry," by R. Burchett, published by Chapman and Hall, London.CHARLES HENFREY, Jun. [5210.]-CART SPRINGS.-Make the leaf blood-hot, quench, and temper by making it hot very carefully till oil will burn on it, or till by rubbing with a piece of dry stick it will sparkle ?-F. J. D. Pr [5212.]-BOILER PRESSURE...t=. ".t thickness of shell; f = tenacity of material; p = 6 times working pressure; r radius of boiler; f=for wrought iron shell 28,600lb. per square inch.-Fux CпOO. [5214.]-PAIN IN THE LEG.-Might not rough worsted stockings prove useful to the patient ? - FRIEND. [5214.]-PAIN IN THE LEG.-As the general health is good, try the following:-Get a medical coil, and one "Smee's cell." Having charged it, take one of the conductors in your left hand, strip the leg and put in a basin of water. Get some one to sponge your leg quickly, and with the other conductor in your right hand touch your leg all over with it. Never mind the pain. Continue for ten minutes the first day, before breakfast. Repeat in the evening. On the the second day repeat treatment, making time 15 minutes; third day, 20 minutes each; sixth day, repeat treatment 4 times, before meals, 20 minutes each. If you do not know how to charge your battery, I shall be bappy to send you instructions by post, if you will send your address to our Editor.-SURGEON. P.S. I omitted to state that when the time is up, dry your leg well, and wrap in flannel, continue treatment for a fortnight. [5215.]-TRANSMITTING STEAM POWER.-Use a four-way cock.-FUM CHOO. [5217.)-BICYCLE CRANK.-I advise "W. G. C." to use a 7in. crank by all means.-FREDERIC W. SHEAR ING. [5236.]-VOLTAIC PILE.-A simple voltaic pile may be made by putting small circular pieces of zinc and copper alternately, and interposing a bit of cloth between the copper of the first and the zinc of the second -i.e., first, zinc; then copper; and, lastly, cloth.-D. GARDNER. ་་ [5237.]-CARTE DE VISITE. "Imowole" will find full information on the subject in Newman's Harmonious Colouring as applied to Photographs," price 1s. DEDALUS. [5237.]-CARTE DE VISITE.-To colour a carte, simply pass the tongue over the surface of the picture, when the paint will easily adhere.-IXION. [5266.]-POLISHING MOTHER-OF-PEARL.-"Holtzapffel "(p. 1094) says: "The pieces (after being sawn) are roughly shaped on the edge of a grindstone into grooves, and afterwards smoothed on the flat side of the stone. Many use soap and water with the stone, &c. Detached pieces are smoothed with Trent sand or pumice stone and water on a buif-wheel or hand-polisher, and are finished with rottenstone. The latter powder is more frequently moistened with a little sulphuric acid, nearly or quite undiluted; this produces a far more brilliant polish."-J. K. P. [5267.)-BALLS.-How does Fred Roe get his iron support for the core out through the fuse-hole, after the ball is cast? All the rest seems right as far as I can see.-J. K. P. [5271.]-ALGEBRA AND DIFFERENTIAL CALCULUS.-Like "F.R.A.S." I cannot undertake to work out sums. "A Manxman" should read the thoughtful letter by " E. L. G.," p. 113. My time is very much occupied, and an ingeniously contrived problem might very unprofitably employ an hour or two of it; whereas "A Manxman," if, as I suppose, he is a learner, would be employing his time profitably in working out such matters. He can gain little by being merely shown how. Still, as this is the first time I have been set to drudgery work, and as "A Manxman" says I must efficiently work out each question and explain each step, I will, at least, make a note or two on his three questions. dr (1) is mere drudgery. Take in each write down the values for ав case; and 1 (), equating severally to 12 pa This will give the required relation, the work is perfectly plain sailing throughout. (2) There is obviously a misprint, as no mathematician would ever write down such an expression as save in an exercise-book for a beginner in algebra. When correctly written this question is probably difficult, though one can never tell till one "tries out" a little. [5218.)--TRANSFERRING ENGRAVINGS, ETC.--Your correspondent "G. P." can best attain his object by aid of photography. If the print or printing be only on one side, a negative on prepared paper can readily be taken by placing the latter underneath the printing or engraving, which must be face downwards, and pressed closely to insure contact. After sufficient exposure to light, and proper subsequent manipulation, he will have a negative from which any number of facsimiles may be printed. The writer adopted this plan very successfully in obtaining copy of a title page of a rare old book, to replace one lost from another set. In this case the leaf could not be removed from the book, and some ingenuity (i) may be written( had to be exercised in order to carry on the experiment. Of course if the thing to be copied is printed on both sides the above plan will not answer, and the camera must come into operation. The reason is obvious, because the impression on the upper side would produce an effect on the sensitive paper as well as that on the under. I presume your correspondent, if not a photographer himself, has some photographic friend who would help him to carry out these suggestions. SENECIS. [5218.)-TRANSFERRING ENGRAVINGS, ETC.-.A facsimile of an old print may be taken in pencil in the following manner:-Carefully blacklead the back of print with some "Diamond Lead," and with a clean cloth rub off all superfluous particles; then prepare a hard piece of wood in form of a lead pencil; place the clean sheet under the print, and with the fine point carefully trace over the lines, using at the same time slight pressure.-TOTNESIAN. [5219.] POONAH PAINTING.-Is it not Poonah dye? Poon-nag is a Bengalese name of the dye-stuff Kottlera tinctoria; or perhaps a name for the paintings on mica, made at Madras, &c.-BERNARDIN. [5219.)-POONAH PAINTING-is rubbing with a hard stiff brush water colour, rather dry, through holes cut in oiled card, which protects all other parts of the paper. This is done with successive templates, till the whole is coloured, on the principle of chromo-lithographs, but is most inartistic and greatly to be condemned.-J. B. PRIMUS. [5224.)-BICHROMATE BATTERY.-Cover tle wire well with wax. The carbon plates will not hurt by being left in the acid; when taken out, wash them with water. [5280.]-MEASURING, ETC.-(Sewers.)-I send for "Country Gabie's" benefit a small extract from "Engineers and Contractors' (not Adcock's) Pocket-book," 1858, about egg-shaped culverts. Depth from soffit of arch to invert 6, diameter of arch 4, diameter of invert 2, radius of connecting arcs = 6, then the area = 1855, or depth as to area nearly as 12 to 37. "Allowing the small error of 3 per cent. in excess, the area is equal to the product of the depth multiplied by the mean of the diameters." I never have built any but round sewers myself, and am rather in favour of that form. I remember, when a student at King's College, a problem was set the class, to decide the form of sewer that would always run the water at the same lineal velocity whatever the depth; and it was proved to be a *Here is an evidence of the impropriety) we almost said absurdity) of carrying on mathematical controversies involving the use of mathematical formulæ in a rapidly-printed,weekly paper. Our circulation is, as Mr. Proctor on another occasion said," so enormous that we are obliged to prepare for press at midday on Mondays. Consequently the composition of the paper has to be done with unusual rapidity. This is our reason why we discourage such controversies. We often wonder, considering the hundreds of letters we receive daily, and the various kinds of writing the compositors have to decipher, that more errors are not made. It therefore may be easily conceived why we discourage mathematical controversies. Mr. Proctor advises "A Manx man" to read "E. L. G.'s" "thoughtful letter," 624, p. 113. He might well do so; in fact, almost all might do so with advantage.-ED has only omitted the shaded corners in the drawing, which together measure four times 3ft. 24in., by 3.0 by 2in., or 9 cube feet. The true contents is 18 yards, and the contractor's way of doing it gives 18 yards.J. K. P. [5289.]-SELF-CENTERING LATHE CHUCK.-Selfcentering chucks are a delusion and a snare for practical purposes. No work will run true in them unless previously turned true in the portion to be grasped by the chuck. The best chuck out is the 4 dog chuck with four separate screws. I consider three screws to be a snare also. "American" 3 dog-chuck ditto, except for exceptional work.-J. K. P. [5295.]-THE MICROSCOPE.-Let "A Poor Microscopist "cut from a cork a ring which will fit tightly upon the end of the eyepiece tube (removing the cap), leave two projections on each side and at right angles to the ring, make a slit on the inner side of these at an angle of 45, slip in one of the round thin glass covers used for slides, and he will have an instrument that will answer almost, if not quite as well, as the Beale's neutral tint reflector described in this week's MECHANIC (I have tried it.)-W. F. L. QUERIES. [5298.]-GLUE.-Will some reader inform me for what different uses the various kinds of glue are most suited, such as the Scotch glue, the French, the town and coignet ?-Z. [5299.]-LARGE INDUCTION COIL.-Will some practical person send me working drawings of an intensity or induction coil (large and powerful one), fit to be used at the lecture table? The quantity and size of primary wire, quantity and size of secondary wire, and the making of the condenser. Advice upon this will be received with thanks by-RAREFIED MEDIUM. [5300.]-IRON CASTINGS.-I have a difficulty to get my iron castings solid on the side which is uppermost in casting, would some brother moulder give me a little advice as to the cause and remedy, and oblige?—A YOUNG MOULDER. [5301.]-SCREW CUTTING.-Where can I procure a book explaining screw-cutting in a lathe ? one that would Also, explain all about the numbers of the wheels, &c. is every maker's lathe constructed in the same way in the screw-cutting wheels ?-ENGINEER. [5302.]-PNEUMATIC QUESTION.-Will any of your contributors inform me of the exact strength with which the air contained in a bladder or sealed bottle presses against the sides of the bottle under the receiver of an air-pump when the air is exhausted? Can the pressure from the enclosed air be equal to 15lb. per square inch, and why? I also wish to know why a bottle filled with water does not get crushed by atmospheric pressure; does the water inside the bottle counterbalance the pressure of the atmosphere?-R. RHODES. [5303.]-WAX BASKETS.-I should be glad if some one could inform me what is used to colour wax red for making imitation coral baskets. I believe vermilion is employed, but do not know how to mix. Also, about how much wax does it take for a middling sized basket? -JAN. [5304.]-PHOTO-RELIEFS.-Can any subscriber give me a formula for producing photo-reliefs? How can I make the arrowroot paper for the diaphanie pictures ?— W. S. CARRICK. [5805.]-BOOKS ON CLOCK AND WATCHMAKING. -I have seen books published as assistants to almost all trades, but never any one to the clock and watchwould inform me if there is any such book or books I should be obliged if some reader making trade. published? If there is, the title, by whom published and the price:-AMATEUR WATCH JOBBER. [5306.]-FLEXIBLE WRITING SLATE 3.-How are they made ?-E. L. G. [5307.)-BLACK JAPAN.-Can you inform me how the pitch is prepared that is used in making black japan, and also how the japan is made so that when put on a coach panel and varnished it does not turn green? H. W. R. [5308.]-WATCHMAKER'S LATHE.—I have a watchmaker's lathe but don't know how to use it, as it is not like other lathes of a medium size that I have seen. It is in fact nothing but a slide bar, with two poppets, a rest, and eight dead centres, differing a little in shape; two of them are of brass, the others, I think, are of steel. If some one would inform me how to perform with such a lathe I should be much obliged.-AMATEUR WATCH JOBBER. [5309.]-CARRIAGE PAINTING.-Would some reader name a publisher of a book of engraved alphabets and monograms as a guide to carriage painters and engravers ?-TOTNESIAN. [5310.]-WATER-COLOURS.-Will some kind reader inform me how the liquid water-colours in bottles are made; also how the moist water-colours in pans are made ?-W. C. C. B. K. [5811.)-SHRINKAGE OF TYPE FROM OVERHEATING IN STEREOTYPING.-The fact raay be as metal, glass, china, ivory, bone, &c., at a low heat, say 170; what would be the expansion per 2in. ? 2. Is there any fusible metal that will melt at 170° or thereabouts, and its composition? 8. Is it known with what power mercury expands? Any answers will be thank fully received.-A. B. C. interesting to metallurgists and chemists, that in the process of stereotyping a forme of types overheated shrinks considerably in height (from face to foot), but remains unaltered in every other respect, so far as can be observed without exact scientific analysis. The metal is apparently as hard, the face is as even and as sharp, and the body is as rectangular and correct as it [5326.]-THE BIRD AND THE BAT.-Will any of was before the accident; but the type is spoilt for print- your readers kindly inform me of the mechanical princiing purposes, as it is too low to take an impression when ples involved in the flight of the bird and the bat, and used with other type. I shall be very glad if any of also wherein the difference between the two modes conyour readers will kindly explain the phenomenon.-sists, or refer me to any work in which I might find such TYPO. (5812.]-SCREW-CUTTING LATHE.-Will our kind correspondent" J. K. P." inform me the proper distance from the centre of mandrel to the centre of leading screw of a 7in. screw-cutting lathe, as I am altering my lathe to make it screw cutting, but don't know the distance to put up my bracket to carry the leading screw?-IGNORANT. [5313.]-POWER OF ENGINE.-Would any reader let me know through the medium of your journal, the pressure necessary to drive a 14 h.-p. high pressure engine to work at its nominal power, and how many revolutions per minute should it go?-J. B. [5314.]-BINOCULAR MICROSCOPE.-Will "H. P." kindly give a sketch of the mode of mounting the prism on Mr. Wenham's plan; also the fine adjustment for the objective of same? I am going to fit it up myself. I thank "H. P." for his notice of my query.-HYDATID. [5315.]-OLD MEDICAL COIL.-Some time ago I received from a medical practitioner an old medical coil, which was minus the contact-breaker. It is of the vertical shape, and the contact-breaker is affixed to two binding screws on the top of the coil, the core acting as the magnet. Isoon supplied the defect and had it working, bat find with one pint cell of Smee's it gives but faint shocks. The power, I find, is regulated by different lengths of the coil brought out and attached to binding screws, of which there are fourteen besides the two for battery connections, which are both marked +. The manner in which the different wires from the coil are connected to the binding screws underneath the baseboard, entirely puzzles me, and I herewith send a sketch of the same, and will thank "Sigma," or any other of your numerous correspondents conversant with the subject, to give me an idea of the rationale of the current. B The wires marked A B and C appear from the thickness to be part of the primary coil; and the others which are of much smaller gauge, the secondary B and C, are connected to the binding screws +. The other binding screws are marked from 1 to 14, the wire A being soldered to No. 14, and the wire Cat its other end to No. 1. The outside circle of dots represent the binding screws, the inside circle the I am also holes through which the wires are passed. at a loss to know to which of the binding screws I should attach the wires with the handles, whether one of them should be placed in No. 1 and kept there, and the other wire shifted from No. 2 to 8, and so on, according to the strength_required? and what sort of battery would be most effective and economical to use ?-ECOSSE. [5816.]-SULPHATE OF LEAD BATTERY.-Many thanks to " Sigma " for his answer to my query, No.5015, but if he will oblige, I should like further information concerning the manufacture of sulphate of lead. He says, any soluble salt of lead is precipitated by sulphuric acid. Does he mean that the salt of lead should be dissolved in water, and then sulphuric added until a precipitate ceases to fall to the bottom? And is this precipitate the required sulphate of lead? And how is it dried from the solution? If "Sigma" will clearly Answer this, I shall feel greatly indebted to him.INDICATOR. information?-T. R. [5327.]-ASSAYING COPPER ORE.-Will any reader of the ENGLISH MECHANIC be so kind as to inform me what spirits and what quantity of spirits are required for assaying the percentage of copper ores, i.e., after breaking the stone (orey stone), from different copper lodes, and dressing or cleaning for market. I wish to know what quantity of copper it contains. By so doing they will greatly oblige-A FOREIGNER. (5328.]-KNEE-CAPS.-Can any fellow subscriber inform me what is the best material for making kneecaps? something strong and durable, and also waterproof.-D. GARDNER. [5329.]-CHUCK FOR CYLINDER.-Would any of "our" correspondents tell me of the simplest and firmest chuck to hold a cylinder, lin. in diameter, by lin. in depth, so as to turn it, not on the flat, but the round edge? If it could be done, I should like one to divide the piece of metal so as to turn two or three flats on it. I wish to have the simplest, as I want to make it my self.-GE. Ss. [5330.]-WHITE LIGHT.-I am greatly in need of an artificial white light, one by which I can distinguish shades of colour; not required to be intense, but regular, and moderate in cost first and second. Is there any plan of taking the yellow out of gas or any other artifi cial light? I have tried tinted glasses for correction, but they do not answer.-J. O. R. [5331.] CONTRACTION AND EXPANSION OF METALS.-If iron be heated and plunged into cold water it becomes hard and contracts, but if copper be heated and plunged into cold water it becomes soft. How is this accounted for? It seems a contradiction of the general law, viz., that all bodies expand by heat and contract by cold.-A CONSTANT SUBSCRIBER. [5332.]-DRY ROT IN WOOD.-Any reader will much oblige by informing me and your subscribers the best plan to prevent dry rot in wood floors. We have had a new floor of the best red deal laid in a new building about four years since, the earth being about 4in. below the wood, and it was so bad in two years it had to be taken up and replaced with an entire new floor. It is only eighteen months since the last floor was put down, and it is going again very fast, and will have to be removed very soon.-YORKSHIRE. [5333.]-POULTRY KEEPING.-Will some kind correspondent oblige me with particulars for keeping poultry? I want to know what profit I could expect per score hens, and the best way to dispose of the eggs and chicks? I have bought a "Manual for the Many," but it does not give the profits that can be made; its instructions are for those that keep them for their own I want to make a living if I can.-FEMALE SUB use. SCRIBER. [5384.]-MODEL ENGINE.-Will some one help me? I want to try to make a model engine to work. What I want to know is which is the easiest sort to make, horizontal, table, or beam? I also want to know all the sizes of each. I should like to have the cylinder lin. bore. I have no lathe, and if, sir, you would find space for a few illustrated parts, I am sure Mr. Baskerville, or "J. K. P.," or some other clever correspondent, would send the same, which would be a boon to a great many. -W. REED. [5335.]-SOLDERING BRASS TUBES.-Will some reader tell me how to make solder that may be used to solder thin brass tubes without the application of heat? [5336.] RUSSIA.-Will some kind reader inform me whether it is necessary that an engineer going to Russia should know the language, and if so, where could I procure a Russian grammar?-H. N. [5817.)-LACQUERS.-Will some obliging reader whow. H. DUNN. is acquainted with lacquering give me the recipes for making a good gold lacquer, a good green lacquer for bronzing, and a pale colourless lacquer ?-INDICATOR. [5318.]-SILVERING CHEAP LOOKING GLASSES. -Can any of our readers tell me the way to silver cheap looking-glasses; also the materials required, and method of using? Having some pieces of glass that I want silvered for a particular purpose, I should like to try and do it myself.--A. M. [5319.)-CHEMICAL AND BREWING.-The water I use for brewing contains a large quantity of iron. How can I get rid of this iron in the water? It prevents the beer getting bright. Would a filter of animal charcoal, vegetable charcoal, and gypsum do? I want some sort of filter which will extract the iron without damaging the water in other respects.-BREWER. Would "InducCONTACT-BREAKER. — [5320.] torium " say what sort of a contact-breaker he uses? 2nd. What is the weight of the primary wire and secondary? 3rd. Would any hard wood do as well as ebonite? Do both ends of his primary come out at one end of the core of the coil? Perhaps "Inductorium" will be so kind as to send a sketch of his coil mounted, the same as "Sigma" did with his medical coil, as I am sure it will be very acceptable to other readers as well as myself.-J. F. R. (5821.] - DRESSING MILLSTONES WITH DIAMOND OR "BORT."-Are there any British manufacturers of Leshot's or any other patent diamondpointed drills ?—M. [5822.]-WORKING SAW BENCH WITH HORSE.I should feel obliged if some reader would inform me how I can work a saw bench with a horse? I have a horse that is not at work half his time and should be glad if I could use him in that way, not having sufficient work for a steam engine.-A YOUNG BEGINNER. [5323.] RHODIUM.-Can any reader tell me how I can detect the presence of the sodo-chloride, oxide, and phosphuret of this substance ?-Z. [5324.]-REMOVING PAINT AND TAR.-How can I remove oil paint and tar from oil-cloths, tarpaulins and other fabrics, so as to obtain the body cloth intact? Can some kind reader oblige?-OLD TAR. [5925.]-EXPANSION OF METALS.-1. Can any reader inform me which is the most expansible substance [5337.]-FILTRATION.-Will some reader describe the process of filtration through which the water goes that supplies London, or any other large town, stating form of sand beds, proportionate thickness, kind of sand and how often renewed or cleansed ?-E. H. J. [5338.]-STEEL BOILERS.-Will any of your correspondents who have had practical experience in the making of steel boilers be kind enough to answer the following questions? Are the plates set cold or heated, holes drilled or punched, price of plate per cwt., and where to be had? Are not steel plates more liable to become brittle than iron ones, after the boiler has been in use for a length of time, making them more difficult to repair? A sketch of a single-tube boiler of the most modern make, mounted with steam dome and showing the ends properly stayed, will oblige; say steel boiler 15ft. long, shell 5ft. 6in. diameter, tube 2ft. 9in., to work at a pressure of 40lb. per square inch, what thickness should the plates be? At the same time, can any brother reader tell me the best practical work on boiler making, where published, and at what price?-VULCAN. [5339.]—HYDROGEN GAS.-Will any reader inform me in what proportions to mix sulphuric acid and water to make hydrogen from iron ?-JUMBO. [5340.]-ULVERSTON PIG IRON.-Will any friend tell me what are the qualities of charcoal lorn pig iron, made at Ulverston, Lancashire, and how it is made, and the class of ores used? I am told it is £10 per ton. -LEARNER. [5341.]-SOAP MAKING.-I shall feel obliged if some of your subscribers will name the best work published on soap making; also the best mode of bleaching palm oil.-H. J. D. [5342.]-SILVERING SPECULA.-Will Mr. E. M. T. Tydeman kindly explain the tartrate of soda process, alluded to in his letter, No. 453, p. 38 ?-HUGO. [5343.]-DRY COLOURS.-I should feel obliged if some of your subscribers will kindly inform me how to make dry colours, such as greens and blues, &c., or name a work which will give the information; also the best work on varnish making.-H. J. D. [5344.]-SILVERING PROCESS.-I should be obliged if any of your readers would give me the title, price, and publisher of a work, or works, on the patent silvering process (nitrate of silver), and also platinum silvering.J. W. RANDALL. [5345.]-ILLUMINATING GOLD.-Can any one give me directions for using "Leroux & Son's " (I believe that is the name) illuminating gold and silver fluid, sold in bottles at 1s. and 2s.? I want to use it with either pen or brush.-DRAUGHTSMAN. [5846.] LEAKAGE IN SLATE ROOF.-I have had a leakage in my roof, "a slate one," for the last eight or nine years, and have had several different men in to see to it, and followed their plans as far as I could, including a new gutter, but still the water comes in every time it rains. Can some of my brother readers suggest a remedy for so unpleasant and disheartening an affair? I may as well add that there are no skylights in the roof, nor does the water drop into the attics, but into the cornice in the second floor, at the side of one of the windows.-OWEN GLENDOWER. [5347.)-MODELLING IN CLAY.-Will a "Working Woman," who replied to query 4975, kindly tell me if any book has been published on the art of clay modelling, a practical and not expensive work? Also whether designs for modelling figures can be obtained? I find it difficult to model correctly without something to copy from.-AN UNSUCCESSFUL MODELLER. [5348.]-THE PHANTOM WHEEL.-I have lately heard an opinion expressed by the captain of a bicycle club in London that an ordinary wheel fitted with a "Phantom "rubber tire is equal if not superior to a "Phantom" wheel (with rubber tire) itself." Can any bicycle riding friends endorse this statement ?-MUZZLE LOADER. [5349.]-A COTTON SPINNER'S DIFFICULTY.— Would any of your numerous readers in the cotton district help a brother spinner out of a difficulty? I have to work a double beater scutcher, and the cotton will stick to the last beater blades, and when it gets on to one side takes all the draught from the other, and so causes one part to choke and make a bad lap. Some time ago we had several letters on cotton spinning which contained amongst many words some good practical hints which were valuable. Could you not induce some of your valued correspondents to write again on this subject, for it is scarcely to be credited, that in such a large trade as cotton spinning, there is not a single practical work on the subject? I know there are plenty of books giving instructions as to calculations, but every one who is in the trade knows that to be a very small part of cotton spinning. If any brother reader knows of any work on the subject giving practical hints I should be glad if he would name it. In the mean time could we not help each other through the ENGLISH MECHANIC ?-B. [5350.]-ELECTRO-MAGNET.I have made an electro-magnet of -iron, and covered with No. 18 cottonThe wire gives thirtycovered wire in four layers. six turns to the inch, and the approximate quantity used is about twenty-four yards. As "Sigma," in his valuable paper says the battery used should be proportionate to the resistance, and as I have not the means of measuring the resistance of the wire on the magnet, I will thank your able contributor or any reader to inform me how many cells of the sulphate of lead, manganese, or Daniell's battery would be required to work the magnet effectively. I wish to apply it to the lifting of a weight of 4oz., placed at the distance of in. from its poles once in every two seconds. Perhaps some of your correspondents would be so kind as to give their opinion as to its capability of performing the work mentioned.-Ecosse. [5351.]-TINNING COPPER.-As I observe from some of your correspondents' answers to queries respecting the sulphate of lead battery that the copper cups forming the negative plate require to be tinned to preserve them from local action, I will be greatly obliged by the information how to tin them. I understand it is done by boiling the article to be tinned in some solution of tin, but that there has lately been an improved method of doing it discovered.-ECOSSE. [5352.]-CLUB WHEAT.-A sort of wheat is called by that name in the United States. Could any brother reader favour me with the explanation of that name?— B. C. W. [5353.] - TRACING PAPER. Could any brother reader give me an economical manner of making tracing paper?-DESSINATEUR. [5354.] - MINERAL INDIA-RUBBER. Elaterit or mineral caoutchouc has been found, it is said, in Australia; where? Particulars will oblige.-M. CAOUT CHOUC. [5355.]-MECHANICAL MANIPULATION.-I wish a few particulars about Holtzapffel's "Mechanical Manipulation." Contents, number of volumes, price, and date of impression.-J. J. TURNER. [5356.]-DRY PLATE PROCESS.-Will some photographic reader furnish me with the formula and manipulation of one of the best dry plate processes for a novice in the art to commence with ?-A WOULD-BE PHOTOGRAPHER. [5357.)-THE POST-OFFICE TELEGRAPH SYSTEM. -Will any brother reader give me instructions through the MECHANIC how to learn the telegraph instrument, as used in the Post-office? By so doing they will oblige, and I think it would benefit my brother readers.-POSTMAN JOE. [5358.]-OIL LAMP FOR MAGIC LANTERN.-Will some kind reader inform me which is the best kind of oil lamp for magic lanterns? There has been a great deal said in back volumes, but nothing about oil lamps. -ZETETIC. [5359.]-TEETH OF WHEELS.-Could any of your readers give a scale and description of the teeth of wheels on the odontograph principle ?-ZETETIC. [5360.1-ENGINEERING ESTABLISHMENTS.-Will some subscriber please state what engineering works employ the largest number of hands, and state the number of hands employed by several of the largest works in the world ?-DRAUGHTSMAN. [5361.)-SELF-ACTING INCLINED PLANE.- Will any reader of the ENGLISH MECHANIC be kind enough to give a rule to ascertain the necessary inclination of a self-acting inclined plane, the loaded waggon to pull up |