[5576.]-PHOTOGRAPHIC SLIDES.-I have been hardened with no temper, the iron keeping the steel successful in obtaining transparencies for the magic from breaking; they are hardened in water, and scarcely lantern by the following process, which I recommend ever come out without running; they are then set on "Saxon" to try. Obtain a good negative, not too dense, an ordinary anvil with a hard-faced hammer, which reby any dry process, preferably the collodio-albumen; quires skill to do: there is no danger of wasters in place this negative in contact with another similarly skilled hands. Eatire steel skate-irons are never harprepared plate in a pressure frame, and expose to dif- dened, because they would not stand setting, and could fused daylight for two or three seconds only; develop not be put together, and are only used for the lower and fix, but not varnish. This should give a clear good class of work.-EKLOM. positive. Now place a small quantity of Canada balsam which has had the volatile portion driven off by heat upon the transparency,and upon this another piece of thin glass; apply sufficient heat to melt the balsam, pressing the glasses together to remove air bubbles; when cold they will be cemented firmly together, and will be ready to be placed in the frame. I have made several very good diaphanic slides for the lantern, and if "Saxon" wishes it I would with the editor's permission give the mode of producing them.-GEO. Fox. [5583.]-PICTURE FRAMES.-The best way of putting small frames together is by winding several thick nesses of string round them after glueing the mitres, and then putting in pieces of wood and drawing them up to the corners, as will be seen by sketch. This does very コロ well for frames of about 6in. or 8in square. For larger frames, say from 12in. to 18in., have a thick flat board, and insert eight large nails or spikes, and wedge up your frame from these. The board must be perfectly true or you will spoil your frame in winding. Be sure to warm the mitres before glueing, or you will not get them close before the glue chills. I keep a board on purpose to put the frames together on. To peg them when they are perfectly dry, put the frame in the bench screw, corner upwards, and cut a cuneiform opening across the mitre with a dovetail or sash saw, according to the size of the frame; fit a piece of wood into the opening, with the grain running in the direction of the hypothenuse of the triangle which it forms; glue it in and leave till dry; clean off. It requires considerable practice to make a good job of them.-T. CoOKE. [5596.]-SPEED OF SAW.-I have found from 750 to 800 revolutions per minute the best speed for ripping up logs of Riga fir, the saw being Sft. 6in. diameter.-J. T. [5607.]-GUANO.-The first cargo of guano sent to Europe was exported in 1841 from Peru, by the Belgian consul, Mr. Bosch Spencer. The manure failing to find buyers in Belgium, the vessel Le National was sent to England, and the cargo was sold, I believe, to a Mr. Meyer, in Liverpool.-BERNARDIN. [5685.] PHOTOGRAPHIC.-A "Would-be Photographer" will be able to get rid of his pinholes and comets if he attends to the following hints:-Pour the bath solution into a bottle and add loz. of a plain 40gr. solution of nitrate of silver; rinse the bath well with clean water, and set it, mouth down, to drain for a few minutes; filter the bath solution twice through double filtering paper, the first time into a clean bottle and the second into a clean bath; coat the plate with collodion, free from sediment. Supposing the sensitiz ing, exposure, and development are perfect, wash well with perfectly clean water. Now for the intensification; have at hand a thoroughly clean developing cup, and pour in one, two, or three drops (for a t-plate) of a 20gr. filtered solution of nitrate of silver, and about 1 drachm of the following solution, fresh and well filtered:Pyro. 5gr., citric acid 10gr., water 2oz. I have found that pinholes caused by a long used bath do not always show till intensification or fixing.-WIRE. [5635.]-PHOTOGRAPHIC.-A "Would-be Photographer" should get his negatives sufficiently dense at once with the iron developer; few operators now find it necessary to intensify with pyro. The pinholes and comets with which he is troubled may arise from crystals of undissolved pyro.; the solution should always be filtered before use. I do not consider the collodion or other chemicals at fault; but greater care and clean liness in the maniplations may, perhaps, produce bett er results.-GEO. Fox. [5637.)-ELECTROTYPE.-Does"An Eighteen Months' Subscriber" mean a single cell electrotyping apparatus? If so, I have one of an improved shape, that will electrotype moulds up to 3in. diameter. I have sent a sketch, = 5152 72ft. per second nearly. The momentum then for 10lb. is 720. Wylson, in his "Mechanical Inventor's Guide," states the time in seconds in which a body falls through a given space = the square root of the quotient of the space in feet, divided by 16-0833. Thus the time occupied by the descent through 80ft. is And the velocity, he states, in feet per second acquired in a given time the product of the time in seconds, and 32-166. Thus the velocity at end of 5 seconds is 5 x 32-166 160-830ft. per second. This is double A. P. Deschanel's quantity. He states that during first second of fall t=8016-0833 near 5 seconds. 8 = 49 12 v = gt And, eliminating t, v=298 Falling force cannot be described in pounds well, as it is but the force of a moment on collision. Thus "momentum" is used for striking force; but whether the momentum is 720 or 1600, perhaps some of your readers may solve. Marrat, of Boston, in his "Introduction to Mechanics" (A.D. 1810) defines the moment of force (when referred to a point, line, or plane) as the product found by multiplying the quantity of the forces by the nearest distance of its direction from that point, line, or plane. If we know the moment and the distance we shall have the quantity of force by dividing the moment by the distance.-J. BARWICK. [5647.]-RULE WANTED.-The velocity per second of falling bodies increases as the sum of the times. Therefore if the velocity at the end of the first second of time be (as it is) 32ft. (nearly), it will at the end of the next second be 64ft., and of the third 96ft. per second. But no rule or estimate of any sort of value can be given for ascertaining the actual force with which the falling body will impinge on another, as this depends on the degree of actual hardness possessed by each substance far more than on any other condition.-J. B. PRIMUS. [5653.1-MARINE SOAP is made from cocoa-nut où and sodium, and differs from ordinary hard soap by being partially soluble in salt water, whence its name.W. H. H. [5607.]-GUANO.-"H. U." is correct in the time that the first was imported in 1841, by W. J. Myers, Esq., of Exchange-alley, North Liverpool. In the previous year one of the masters employed by the above. pended the moulds, G. The edges of the pieces should peculiarities at least of my own adding, which are I con named gentleman brought one of his coal casks full, which was tried by William Skirving, Esq., nursery man, Liverpool. Being found very strong and a good manure, Mr. Myers imported a cargo of 500 tons, which was very quickly sold at £20 per ton by Mr. Skirving. A year or two later, Mr. Myers, in company with Messrs. Gibbs, Bright, & Co., purchased from the Peruvian Government for £200,000 the sole right of getting guano for a certain number of years (I think ten or twelve), and took out of bond about 400 tons of the above quantity. -J. W. M. [5610.]-WHEAT.-I also am anxious to know what is the highest latitude at which wheat can be grown. According to the "Synopsis of the Vegetable Products of Norway," by Dr. F. C. Schübeler, Christiania, 1862, wheat has not hitherto been cultivated in that country, in fields, further north than lat. 64° 40; but in the halfcrown "Physical Atlas" of Mr. Keith Johnston, I find for the northern limit of wheat in Europe, a line passing through Scotland and the south of the Baltic Sea. There must be an error in one of these statements.-BERNAR DIN. [5611.]-STARCH.-"H. P. H." says, in answer to "Thomas," starch may be regarded as a "single vesicle or cell containing a semi-fluid mass of about the consistency of blanc mange." I will give reasons for thinking otherwise. If you take some dry starch, the larger the better for observation, say potato, and pound it in a mortar, many of the grains are smashed, as may be seen by putting a portion under the microscope; yet we get nothing but dry dust. How does this consist with the above idea of its constitution? I think treating starch with a little iodine, and adding sulphuric acid, or even carefully heating in water, and watching the results under the microscope, will make its constitution plain; the various layers swelling out, and ultimately becoming dissolved or diffused in the liquids. Young starch granules are smaller than the more mature, and frequently without any markings. The nucleus appears to be the centre of formation of the starch grain; some regard it as marking the point of attachment to the surface on which the starch is formed. The starch grain is ordinarily coated with a substance probably of a nitrogenous nature, which produces the discoloured appear ance in unbleached starch.-J. C. in.-B. G. [5626.]-TELESCOPE.-A 4" speculum is fastened, by means of three springs, attached to cap of tube, which hold it tight upon the cap or bottom being screwed [5627.]-FASTENING LEATHER BANDS.-The best isinglass dissolved in strong alcohol answers well. The splice ought not to be less than 6in., and evenly shaved; clamp the joint between two slips of wood.-J. T. [5632.]-SKATE-IRONS.-" Skater" wants to harden a pair of skate-irons without warping. I suppose he means by warping running from a straight line-i.c., crooked, known in the trade as runned. Skate-irons are made from iron and steel, and all steel; the former is used for the better class of work, and alone should be which will require but little explanation. A B C, box of planed pine, fin. thick. D, porous plate. E, plate of zinc, with strip passing to copper rod, F, from which are susbe coated with hot pitch and screwed up by the screws, A. The part B should be filled with a solution of sulphate of copper, 6d. per lb., containing a little sulphuric acid, and the part C with water six parts, sulphuric acid one part. A porous plate can be made by grinding a will do, but the thinner the better. It can be fixed in common flat red tile to the required thinness, about fin, its place by cutting a groove in the box 2in. from the end, and sliding the plate in with hot pitch, which will prevent the solutions mixing. d, direction of current. -WIRE. cigar boxes, with a flat rim glued round, fin. broad and [5643.]-IMPRESSION OF SEAL.-"Sub Sigillo " [5654.]-CHEAP AIR PUMP.-I send sketch of air pump, which I constructed at a cost of less than 1s., and which is as effectual as if it had cost £10. It is very similar to an air pump known as Tate's, but has two sider improvements, inasmuch as they do away with the necessity for good workmanship, and the merest novice can make an effectual instrument. It consists of a tube which need not of necessity be perfectly true, nor even smooth (but should at any rate have some pretensions to these qualities) with a movable bottom, a movable top, and a stop or diaa conical hole in its phragm at C,having centre, the largest diameter of which is greater than the piston rod which passes through it. This stop is a fixture, and the hole in it is made conical for reasons you will see presently. The piston rod is a piece of stout iron wire well cleaned from rust, to one end of which is soldered a circular piece of brass to form the under side of the piston; over the piston rod slip a piece of small copper tube, and over this again ansther piece of the same, as shown in the B; There drawing at solder all together; tap a circular piece of brass as shown at E to form now cut a thread on the last piece of tube, and the upper part of the piston. Now cut a circul ar piece of pretty thick leather, about in. larger in diameter than the tube, and having pared it from the centre gradually thinner towards the edge, slip it on over the wire and screw the top piece of brass down on it, and you kave the piston made. is no valve in the lower part of the apparatus, a small piece of pipe is simply soldered on to the side of the tube about lin. from the bottom; this done, a very small afterwards scraped off from the inside with a penknife. hole is to be drilled through into the tube, and the bure The upper valve consists first of a circular piece of india-rubber, through the centre of which passes the piston-rod rather tightly; above this is an ordinary iron washer, and then a spiral spring made out of a piece of brass wire by simply winding it round a pencil or penholder; and above all, the top of the machine, which has a hole in the centre as nearly the size of the piston-ros as possible; this has also four holes to allow the air to pass out. The action will be easily understood: the tin funnel, which forms a part of the top is filled with oil, the piston rod is forced down to the bottom of the cylinder; communication is thus made through the hole Fwith the receiver. On lifting the piston, communication with the receiver is cut off, the air above the piston is compressed until it forces up the upper valve, or until the small piece of copper tube comes into contact with the india-rubber (which it should do each time) and so allow it to escape. The piston at each stroke should be allowed to remain at the top for a moment to allow the air to escape, and the oil from the top to descend on the piston, which thus becomes, like the top valve, hermetically sealed. Now, whatever inequalities exist in the pipe, instead of allowing air to pass back into the receiver, these will rather allow the oil to pass, which accumulating each time at the bottom of the pump, will each time the piston descends, be forced above it again, so that with ever so rough a tube in reason, and ever so badly constructed an apparatus, results may be attained which the more expensive apparatus cannot exceed. With this contrivance, which I have made out of one of the tubes of Palmer's candle lamps, at the expense above mentioned,. I can exhaust a large paraffine chimney in about ten strokes of the piston, and have performed all the ordinary vacuum experiments with electricity, &c. P.S.-The handle should be ma de to screw on and off, and in putting the machine tog ether, pass the rod up from the bottom, the edges of the leather, of course, turned upwards, as in sketch; afterwards screw the bottom on. In the absence of anything better, the bottom may be even stopped with a cork and sealed. -HECTOR. B [5654.]-CHEAP AIR PUMP.-Perhaps the enclosed sketch of air- pump will meet the want of "C. H. H." R is a tube connecting the pump with the receiver, K. There is a valve, V, at the bottom of he cylinder, and, another valve VI, in the piston P, both opening downwards. The piston works air-tight through a collar of leather at the top of the cylinder. When the piston P is pressed down to the bottom of the cylinder, all the air which it contained will be forced out at V. When the piston is drawn up, the valve V closes, preventing the entrance of R air from the atmosphere; and whenever the piston passes the tube, R, the air from the receiver immediately rushes into the cylinder, another descent of the piston expels this volume of air, and thus the action goes on. The valve V in the piston prevents any accumulation of the air in the cylinder, after the piston rises above R, and enables it to act smoothly and equally. By this simple contrivance the process of exhaustion may go on indefinitely, there being no valve of any kind between the cylinder and the receiver. (Extracted from Cómstock's "Natural Philosophy.") This is certainly a simple and cheap instrument. If "C. H. H." is any way handy he might make one for a few shillings. JUNIUS. [5655.]-OPEN PEDAL PIPES.-Richard Walker will find this a good scale for his organ:-CCC, 8in. wide, 9in. deep within; CC, 44in. wide, 5in. deep within; C, 2gin. wide, 5lin. deep within; height of mouths from the block, a shade over the width, for 2in. wind, for 3in. wind cut a little wider.-SHEFFIELD SUB. [5656.]-PARAFFINE LAMP.-The cause of the formation of soot at the corner of the wick is that the aperture in the cap over the burner is not large enough. If" J. F. R." will take a small round file and cut down the cap a little on the side the defect occurs he complains of, that will remedy it. I should also advise him to soak his wick in strong vinegar and well dry it before putting it into the lamp, which will prevent all smoke. -G. H. S. [5658.]-HARD ALLOY.-See reply to query 5575.J. N. D. C. [5660.]-QUICKSILVER.-This is probably impure, and may easily be cleansed by distilling in an iron retort, the nozzle of which should dip in cold water contained in a bowl or other suitable vessel. The operation is more safely performed out of doors in case of any accidental escape of the highly poisonous fumes. If a retort is not obtainable, "Hammersman " may make one by welding up one end of a bit of two-inch gas tube (say eight inches long) the other end of which has the usual thread. Then close one end of a corresponding screwed coupling, by either welding or screwing in a disc of iron, in the centre of which the end of a bent gin. or in. gas tube is screwed. This forms the cover which, when screwed on, should be tested with fire or other clay. Perhaps & simpler retort may be made with a small glue-pot pan, or other similar iron cup, covered by a piece of thin boiler-plate, cut in shape of Fig. 1, and with the three lugs bent over so as just to pass over the edges of the pan. One or more wedges between the lugs and the flange will then secure the cover, which, after charging the retort with the mercury, should be luted as above. Fig. 2 and 3 are sketches of both retorts. A wood fire will be sufficient.-J. T. [5663.]-DEFECTIVE COIL.-The fault is evidently in the battery. Although "Inquirer "gives the solution of his battery, he does not state what the elements are. Very possible the fault is polarization of the negative elements. Whether another battery would give a stronger shock depends on the construction of the coil, but most probably it would.-MECHANICUS. [5667.]-TELESCOPIC.-In answer to "Scorpio," p. 239, I send diagram of a simple and efficient method o mounting a diagonal plane for a reflector, which will [5668.]-FACING STONE STEPS.-Use Portland long, 1in. wide by in. I always use a zinc cylinder, about Sin. diameter a id 8lin. high, but two slips of zinc, 14in. wide and 9in. high, placed in the containing-jar opposite the broadest sides of the carbon will answer as well. You have no need to use very thick zinc, ordinary sheet-zinc will do. Use as large a porous cell as you can get; 3in. by 9in. is a capital size. The dioxide is the black oxide, represented chemically by MnO2.A. J. JARMAN. [5692.]-FISHING-ROD FERRULES.-Has "Salmo" tried" Brunswick black" for his fishing-rod ferrules? I use this and have found it answer very well. I do not know what it is that tackle-makers use for the purpose. -MUZZLE-LOADER. (5692.]-FISHING-ROD FERRULES.-Warm the ferrules and paint with sealing wax varnish, i.e., black sealing wax dissolved in methylated spirit; the solution may be made either hot or cold: the same is used for blacking and varnishing bindings of rings or of splices, and for many occasions in fisbing-tackle making and mending where a non-elastic varnish is required.WORKING WOMAN. [5698.]-TURBINE WATER WHEELS.-Mr. Gleed will find many examples of the modern turbine, both at work as well as in print; but notwithstanding their supposed theoretical perfection, I should advise him to adopt the original simple form of which I enclose a sketch in outline. I presume from his giving the presure at 201b. that he has an available fall of about 30ft.. which will produce a very great power in a very small compass. Turbines have been at all times universally in use in mountainous countries, where high falls with moderate streams continually occur, and the proper name of this water wheel is "Ritrecina." The design is an accurate drawing of hundreds of existing water-mills RIGHT HAND SHOOT 9IN [5670.]-NEURALGIA.-I can fully sympathize with "J. C. G." as regards that painful complaint, neuralgia. Having had several severe attacks of it myself years ago, and in the same spot-the back of the eye-I am in hopes that the remedies I have found effective may prove so with him likewise. The great point of course is, to prevent the attack on the slightest symptoms being felt; and neuralgia always gives a good warning. Take about 3 grains of sulphate of quinine twice in the day; or, if "J. C. G." does not find quinine disagree with him, as much as 4 or 5 grains. This knocks down the enemy at once; at least I have always found it so. Do not neglect the slightest warning, but take the quinine at once. Should the enemy, however, have working with a 30 ft. ¡pressure of water, more or less, obtained a lodgment, the only effectual remedy I can with less than a 2in. nozzle, and driving one pair of mention with any confidence is extreme cold. A stream 4ft. 4in. heavy stones, grinding at the rate of six bushels of very cold water long continued, ice, or ether-spray an hour, clean bran and fine flour. It is supposed to bo have been with me most effectual; it is a slightly pain- constructed of wood, but iron, of course, will do as well, first; but let "J. C. G." persevere and he will not repent ful remedy, as it a little increases the reuralgic pain at it.-H. C. K. [5670]-NEURALGIA IN THE FACE.-There are no specifics for disease. It is the patient, not the disorder, that requires treatment. The causes of neuralgia are numerous, and therefore the treatment must largely differ to be successful in many cases. The vaunted remedies for neuralgia are based upon the fact that (excepting in disease of the nerve structure or surrounding tissues) neuralgia invariably ceases of itself within six months, even if it recurs every year, as in "J. C. G.'s" case. If "J. C. G." would send his address to the Editor for insertion in the Sale Column, I would gladly write a note to him on the subject, having formerly suffered much from the complaint myself, and having therefore much sympathy with other sufferers. -S. [5678.]-TRICYCLE.-From the result of my experience I should advise "Griffin" not to use ratchets on the driving wheels; but to fix one wheel only to the crank axle on the off side, and let the other wheel run free, which I find answers very well.-HAMLET. [5677.]-PNEUMATIC SHUTTLE.-The pneumatic loom, as exhibited in the Islington Exhibition, and previously in the Belfast Exhibition, is patented by Messrs. Moreland & Coulong, of Belfast, from whom a detailed account of it may be obtained. The shuttle is impelled by atmospheric pressure. The box at each end of sley is lined with cork, and covered over the top, so that when the shuttle enters it is comparatively air-tight; the back of each box is fitted with cylinder and piston, the rod of the latter being connected with, and actuated by, a crank placed on each end of crank-shaft; the cranks actuating the pistons are so placed that when the sley is moving away from the face of cloth, the pistons are moving forward; a connection between bottom of cylinder and enclosed part of box allows the air thus compressed pop-gun. Although the patentees claim a good many advantages for it, as a practical individual in the working of power looms, I do not think it is destined to become a successful rival of the many methods now in use for throwing the shuttle. Apropos of looms and weavings, I should be glad to see far more queries and letters on this useful industry, as few people are aware of the extent to which power-loom weaving, in some of its most intricate branches, has developed itself out here in Ulster. In the production of flax-woven fabrics, from the finest damask to the coarsest grey Holland, I may say it has no rival.-LEH TEB. to act on the shuttle in the same manner as the child's [5677.]-PNEUMATIC SHUTTLE. A pneumatic shuttle is precisely the same as an ordinary shuttle, except that it has the parts between the "cap-hole" and the shoulder about 1fin. long, and the same shape as the inside of the shuttle-box, to act as a piston. That referred to at the Working Men's Exhibition was not so made, hence the great escape of air, and the chief reason for the excessive power required to drive that pneumatic loom. The writer's experience says: don't waste time and money on pneumatic looms.-GARDE LE ROY. [5689.]-MANGANESE BATTERY, ETC.-In reply to "Mechanicus," the size of carbon block I use is 9in, FEED TRUNK 90 FEET if more suitable to the views of the constructor, and it may be reduced in its dimensions to suit any kind of work required. It should be noted that the "Ritrecina" or turbine is only, however, used for speedy work, never for slow or heavy motion.-H. W. R. [5696.]-VIOLIN.-Mr. T.W. Boord seems to forget that the soundpost is placed on the right side of this instrument, therefore a bar which runs through the centre of the violin cannot disturb it in its place, neither will it interfere with the position of the brace, which strengthens the inside of the belly, as that is glued along on the left, and the bar lies between both.-EDWARD B. FENNESSY. [5702.]-FROM A. J. JARMAN.-"A Beginner" cannot make his own gas-carbon. It is a residuary product of gasworks. Go to any gasworks and ask one of the stokers for a piece of scale that gathers in the retorts; he will understand you. This obtained, you can cut out pieces as you like, and save the dust to mix with the manganese. The containing-jar is an ordinary large preservejar. The porous cell must be obtained from an electrician, which can be obtained anywhere at 1d. per inch - that is, 6in. round porous cell, 6d., &c., meaning 6in. high. The cap is not riveted; it merely clamps the carbon-block. Mr. Wm. Tonkes,-You are quite correct respecting the letter on p. 81.-A. J. JARMAN. [5704.] GAS. It would scarcely be worth while to put up a retort, &c., for two lights only (I preto attend to it oneself would grow wearisome. Where sume "J. M." means single jets), the bother of having establishments are situated away from public gasworks and use, say, 20 lights and upwards, it pays well to have a properly arranged gas apparatus, which the gardener can attend to as well as his daily work. The gas will not then cost more, but something less than town gas. But if" J. M." still wishes his queries answered he shall receive satisfactory replies in a future number fromGARDE LE ROY. [5704.]-GAS.-Will not " J. M." find an 8in. retort too small to be economical?-BEN. G. [5705.]-BIRD STUFFING.-If it be a dried skin it must be steamed on the flesh side till flexible, taking care not to wet the plumage. If the bird has to be be skinned do not wet it, but make an incision from the point of breast-bone to vent. Strip the skin down on each side till joints of wings and legs can be reached; cut off these and the rump, and strip skin off the back and neck to the skull turning skin of neck inside out; cut off neck from back of skull and remove eyes and brains. Strip legs and first joint of wings in like manner, and remove flesh from bones, and remove flesh from second joint of wing by cutting on underside Then form body of tow tied into shape by packthread, Double a piece of fine wire and twist the doubled part of it to a length sufficient for the neck and passing the two ends on each side of the body twist them firmly together just under where the tail will come and leave putty and lap tow round the twisted wire to form the their ends projecting to support it. Fill the skull with neck, also round bones of legs and wings to replace the flesh removed. Put the tow body into the skin, sticking the end of the twisted wire into the putty to support the head, and if all seems right sew up the skin. Then run pointed wires up the hollow part of the bones of legs and through the body, clenching them in the tow on the other side. Then set up the bird, putting it in the desired attitude and supporting the wings by pins or wires till the skin dries, when they may be removed; stick the eyes into the putty. For preserving the skins, dress with 2 parts powdered arsenic, 1 burnt alum, 1 cayenne pepper, and for success. practice, quantum sufficit.-J. B. PRIMUS. [5707.]-FRENCH POLISH.-Take twopennyworth of alkanet root, one pint cold-drawn linseed oil, and one pennyworth rose-pink, or more alkanet and pink if the pinky shade is desired deep. Leave all together in a pan over night, then rub on your table in morning. Leave it on one or two hours, then rub off with linen cloth. A beautiful gloss will be the result.-M. DUFFY. [5707.]-FRENCH POLISH.-Deep scratches cannot be removed except by glass-paper and repolishing. Dulness of polish may be remedied by a thin fresh coat on the old one.-J. B. PRIMUS. round the copper; cut a strip of sheet zinc, an inch wide into pieces, which turn round a rod into cylinders large enough to surround and grip the jacketed copper, and solder the wires from these to the next zinc in series. A chain is thus formed, which though not quite so convenient, will cost a halfpenny for each shilling a purchased chain would cost, and be just as effective.SIGMA. The fattening fowls in coops. Buckwheat meal is considered [5719.]-EBONITE.-Ebonite is a compound of sul [5720.]-STOVE.-Musgrave's slow combustion stove will fully answer the requirements of "M."-VIVIS [5744.]-TO PICTURE FRAME MAKERS.-"Amateur" phur and india-rubber combined under heat and pres-ornament. It is composition ornament, and is made as will require a sulphur or plaster mould to cast the sure (i. e., high pressure steam), it is but another name follows:-Mix 71b. of glue, 341b. of rosin, lb. of pitch, for vulcanite.-R. N. 14 pint of linseed oil, and 2 pints of water (more or less as you want). Boil together, stirring till dissolved stir into it whiting as much as will render it of the cos sistence of putty. Press it into the mould, which o first. Mix only what you can use before it gets hardened, as you must steam it if required to be worked again. You may stove it a little to dry quickly, then remove it from the mould, and glue on your frame; make secure with needle points or brads.-M. DUFFY. SPERANDUM. [5720.]-STOVE.-Dr. Arnot's is the best. If Welsh coal be used, and the stove fitted with the self-adjusting draught apparatus, it may be left for hours untended. I also prefer the open fireplace invented by the same ingenious physician, which is lighted at the top and fed from beneath, both for cleanliness and economy. Having tried many methods I speak from experience.-consciousness at about seven miles of height. The speed [5746.] BALLOONING.-Mr. Glaisher began to lowe of a balloon depends entirely on that of the wind as it travels with the atmosphere, not through it.-J. B. H. B. M. [5721.]-EXECUTOR'S ACCOUNTS.-Merely make a [5724.]-GLUTEN. - Gluten is insoluble in water, [5708.]-HYDRO-ELECTRIC MACHINE. It is im-J. B. PRIMUS. possible to make this machine cheap. In the first place, it requires a high-pressure boiler insulated on glass legs, provided with a row of jets of iron tube (about 40 or 50) with brass mounts, containing partridge. wood mounts, with about fin. hole through them. The boiler should be capable of standing 80lb. pressure of steam; the prime conductor is a zinc-lined box, containing rows of points to collect the electricity from the jets. The electricity is generated by the friction of steam against the wood jets.-R. N. [5712]-SILVER COIN.-In reply to "O. E. S.," I beg to state that I cannot find his coin mentioned in any numismatic works that I have. If it is genuine, it must be very rare, but I am strongly inclined to think it must be a forgery. If "O. E. S." lives in London he should show it to some large coin dealer, and ask his opinion, or to same competent numismatic friend.-HENRY W. HENFREY, M.N.S., &c. [5712.]-SILVER COIN.-The coin mentioned by "O. E. S." is one struck after the death of Faustina Sen., and the inscription refers to the asylum for orphans established in her honour. It is mentioned in a catalogue before me, and, if genuine, "O. E. S.'s " specimen is worth about £2.-S. J. H. [5727.] POLISHING EDGES OF GLASS. - York stone and water will smooth the edges if not splintered, [5728.]-MAGIC LANTERNS.-" K. M. E." can do as I PRIMUS. [5746.]-BALLOONING.-1. Mr. Glaisher was within the barometer fell to 12in.; but what altitude this really an inch of his life, as he believed, by ascending to where indicated is quite uncertain, as no direct measurements of balloon heights appear to have been yet made. They would be easy with two passengers possessing sextants, and able to use them simultaneously, while a third read the barometer; or might even be managed with one sextant. 2. The rate at which balloons travel is precisely that of the wind; indeed, they have no motion through the atmosphere," the flame of a taper being said to be absolutely unaffected, except at the moment the balloon is in one wind and the car in another.-E. L. G. [5746.]-BALLOONING.-Messrs. Glaisher and Coswhich point faintness and difficulty of breathing in well on one occasion reached a height of seven miles, at creased to such an extent as to endanger life. The speed attained by a balloon varies, of course, according to the wind. With what sailors call "half a capful," miles an hour have been accomplished.-VERTUMNUS. [5752.]-PIANOFORTE PINS.-Apply a red hot piece of iron two or three times to the broken wrest pin. If any hold at all can be got of it, it will be easily re moved; otherwise it will be necessary to drill it out.R. A. M. [5756.]-WHEEL-CUTTING ENGINES.-W. G. Wil. liams will find all about the adjustable interpolator is Rees's "Cyclopædia," at least, that is the work I was referred to by the gentleman who furnished the photos. from which the engraving on p. 12 was done. I have not seen it myself, but there is only one way that I can see open for using the instrument. Say you want 101 teeth from a row of 100 divisions: measure the diameter of the circle of 100 holes, and calculate its circumfer ence, and divide that by 100 for the distance from hole to hole; then as you are to get 101 divisions into the space of 100, it is clear that the distance between the 100 new holes will be of that of the old ones, and the 101 [5713.]-WELSH GROIN (2).-It has occurred to me since giving the reply on p. 261, that the word "Welsh " is here, very probably, a corruption of gauche. The French, on the first introduction of groins of double curvature, must have called them "ogives gauche," and the English for ogives being groins, a most natural anglicizing of the above would be "Welsh groins." The ogives or groin-ribs of medieval vaulting, which were indeed the fundamental and formative organ of the entire architecture that we call "Pointed" and "Gothic" (but which the French know by the perfectly true and philosophic name ogival), were never twisted, "gauche," or allowed to deviate from a vertical plane; and the way they nevertheless were adapted to bear two in-flanges to slip under these. It is handy in packing and alidade will have to be shortened or lengthened by the tersecting vaults of unequal height may be seen in the example I cited, the nave of Winchester Cathedral (A.D. about 1400) or the later one of St. George's Chapel, Windsor, the only two cases I remember of this problem, for which moderns would have resorted to "Welsh groins."-E. L. G. [5718.]-WELSH GROIN.-Germans call their neighbours over the border "Walsh," whence the appellation of the Celts in Wales given to them by the Saxons, and of our walnuts, which are of Lombard origin. The name Tedeschi, applied by Italians to men and things German, is not a German word, as stated in a note in the ENGLISH MECHANIC some time ago, but the nearest approach they can make to the pronunciation of "Deutsch,"which is what the Germanscall their language. And, if I recollect rightly, it is Professor Max Müller who gives us the above information, and says, too, that Deutsch is derived from " deuten," and means signifi. cant."-J. K. P. [5717.1-CACTUS.-With regard to the culture of the cacti in this country, it is found that, generally speaking, they ought to have a season of complete rest, followed by one of violent excitement; that is, they ought to be kept almost without water from October to March, and then watered profusely while they are coming into flower. They ought all to be grown in pots well drained with cinders, instead of potsherds, as the latter retain too much moisture for the delicate and succulent roots, and they all enjoy bottom heat, which makes them throw out abundance of fibrils. When received late in the year-that is to say, in October or later they should not be potted till the following spring; and when raised from seed (which is frequently sent over even in dead specimens) the seed should be sown in silver sand, and the yonng plants when transplanted should not be watered for several days.-H. C. d. [5717.]-CACTUS.-Cactus should be grown in pieces of broken brick, old mortar, and sweepings of floors; should be kept in a dry house, and get very little water; once a month in winter, once a week in summer, will be often enough to moisten the soil, taking care to allow no water to go on the plant.-VIVIS SPERANDUM. [5717.]-CACTUS.-You may grow cactus in old mortar; no water during winter, plenty in summer, and syringe the leaves.-W. HOLMES. [5718.]-POULTRY KEEPING.-I am of opinion that there is no operation connected with the poultry yard which requires greater attention and experience than also for showing with opaque lantern, which does instead [5729.]-STEAM BOILERS.-I am afraid if "W. A." [5780.]-STRENGTH OF BOILERS.-Strength of good boiler plate, average quality, = 44,8001b. per square inch, sectional area of the plate's thickness, multiplied by the thickness of the plate, divided by the internal diameter in inches, gives the bursting pressure in pounds per square inch. Allowance for riveted joints being as follows:-Strength of plate = 100, double riveted joint 07, single riveted joint 56. Testing bar iron is usually done by breaking a piece off the end of bar, and carefully examining the grain. So also is boiler plate, but I usually examine the burr, which is punched out of the hole, and if found to be mushed or badly cracked upon the die side, I condemn it at once. Indeed this is a very good test for any kind of flat bar iron, as well as boiler plates.-BOILERMAKER No. 1. [5731.] EARTH CIRCUIT. Yes. The current returns to the sending station by the earth.-BEACON LOUGH, [5732.]-HORN SPOONS.-Horn spoons are made in and should not touch the skin; it may be prevented by 100 100 difference between and for every successive Tul division, according as in working you turn the plate of the machine round "with the sun," or the contrary. I gave my substitute for the wheel gauge, with description W. G. W." The gauge, as sold by the rule makers, is of its use, on p. 328, Vol. XI., to which I must refer divided on a boxwood rule, about 20in. long, beginning with about No. 5 gauge, and the very small ones are done on a sheet of brass about 8in. by 3in. The numbers correspond to that number of parts to an inch-thus, No. 10 gauge is tenths of inches, and the corresponding wheels have ten teeth for every inch diameter, always recollecting to add two divisions to the pitch diameter for the height of the teeth above that line. I think the wooden rules are 12s., and the brass ones about 7s. or 83. but any scale of divisions of an inch will do as well. As, for example, most rules are divided to 8, 10, 12, 16 parts to an inch on one edge or another, and would serve for those gauges if you only bear in mind the two extra divisions wanted to every wheel, of whatever size, for the points of the teeth.-J. K. P. passed through an aqueous solution of sulphate of cop- The solution of proto-sulphate of iron remains un- Hg Cla+SH Hg S + 2HCl A At first, when only a small quantity of SH is present, Co спл Co Pbo" + SH2 PbS + 21 Co Ho ONE WHO DID IT. [5767.]-WATER PIPES.-A pipe 24in. in diameter will pass more water than two pipes 12in. in diameter.H. E. M. [5769.]-DIVIDING PLATE.-My old dividing plate, by Holtzapffel, on a wooden pulley of 5in. lathe, is of brass, 11-64 thick. If your pulley is of metal, whether gunmetal or iron, the divisions may be drilled into the solid, which is much better than a removable plate. Of course you should have your pulley made with a broad rim on the face for this purpose. I consider iron by far the best for a real workman's, or, indeed, any lathe.J. K. P. to QUERIES. [5845.]-TELEGRAPHIC.-Will some of the readers It was stated some time ago, at an inquest held in (5777.] LATHE HEAD-STOCK. In answer J. K. P. [5793.]-LATHE.-I have left a query or two of Tom Brown's unanswered, thinking that the contents of p. 256 would enlighten him. He must recollect if his two fifty wheels just reach the distance, that the slide-screw will have its motion reversed for want of what he calls his carrier. In explanation of the numbers given: if your screw has ten threads per inch, and you always drive with a fifty wheel, then you must put on the slide screw a wheel of five times as many teeth as the number of threads you want; and the numbers I furnished, taken in succession thus, suit for 11, 12, 14, 16, 18, 20 threads per inch, which are Whitworth's pitches from down to tap.-J. K. P. [5794.]-ARITHMETIC AND ALGEBRA.-Barnard Smith's book, which I have little more than seen, is as good for self-instruction, I should think, as any other. For the step from merely elementary algebra to the ininitesimal calculi, its chief applications, I would recommend the late Professor Whewell's "Doctrine of Limits,' especially if there be any new editions, as the first was, unhappily, very badly printed. Any of the works of Professor De Morgan are to be valued, he being, as I think, by far the best living popularizer of mathematics, high or low.-E. L. G. [5806.]-TIN CAN.-"H. W. R." must again have "omitted a coefficient" or something, to make the area of a circle whose radius is √2 8·1416011. It is 6-2831858 = 2, which I called 2, merely meaning that it was 2 of the units I was using for comparison. Insert after this, and each of my other figures, and all will be right. The sides of the same can are = 4, while the sides and bottom of the 78 can (of Mr. Revely's form) are each 3, making the whole surface of each of these cans equal, namely, 6. What I undertook to prove (if he will look again, p. 163) was not that my can had the maximum capacity, but merely that he was wrong-that his had not the maximum. How this could be proved, without calculating surface and contents of two cans, one of his proportion and another of a better proportion, I cannot see. These two have their surfaces, in square units, each = 6; while their contents are, in cubic units, his == V8 = π 132 .-E. L. G. = π and mine (5809.]-HEADSTOCK.—TO “S. D."-The section of your bed is very much what mine is with a 5" head, but is very short; not but what a short lathe is useful for many, indeed, the majority of purposes.-J. K. P. [5814.] WILDE'S MAGNETO-ELECTRIC MACHINE.-I do not see my way to helping "Infelix" nuch, unless by the suggestion that possibly he is revolving both armatures at the same speed, and makes the breaks synchronous. In this case, of course, the current from the first would not be developed in the second; otherwise, his failure must be due to some errors of construction, which can be discovered only by Inspection.-SIGMA. [5818.]-DEXTRINE.-A form of dextrine, known as British gum, is used in calico printing as a thickener. -CHEMICAL. (5823.]-AIR-GUN.-I always pump in the air until I can do so no longer; and, as I have never met with any accident, I presume there is no fear of bursting the breech. Mine was made by a good London maker. It is adapted for shot or bullet. If using shot, I first send down a wad, then the shot, and, last, another wad. With a well-fitting bullet, the wads may be dispensed with. For a description of the mechanical arrangements, I Taust refer "Gamekeeper" to the indices of back volumes. I remember seeing an illustration some time back.-W. L. 20. MAINWARING. [5848.)-ETHENE.-Would any kind reader oblige me BODY."-Will "Nobody" kindly inform me the price mentioned by him?-COMPENSATED BALANCE. [5850.]-THE QUEKETT CLUB.-Will some one A flat.-S. MADDISON. [58521-SKATES.-Will any subscriber kindly tell me the best way to make a pair of skates to fasten without any straps, and show parts of them with size, &c., and oblige-ONE WHO LIKES SKATING? [5853.]-SCHOLARSHIP.-Could any of my fellow readers imform me if there are any scholarships open to competition in connection with the Royal School of Mines, or any other technical educational body, the examinations for which are conducted by the Science and Art Department? I once heard that there were a few preparatory scholarships given to intending competitors for the Whitworth Scholarship; if so, could any one tell me the conditions and subjects of examination in these? -W. C. ROYALT. (5854)-DRAUGHTSMEN'S DUTIES.-What are the duties of draughtsmen in a large engineering establishment? I wish to make myself competent for that job, if I can. I am a fair mechanical draughtsman, but have little mathematics beyond the elements.-W. C. ROYALT. [5855.]-STOPPING AND FRENCH POLISHING.— Would any reader inform me what "stopping" is generally used by French polishers to fill up the pores in new wood before polishing, and how to make it; and, also, how to make the kind of glaze that is used to finish a cheap job-what is termed fiddle by a good many polishers ?-ONE WHO HAS GOT THREE MORE SUB SCRIBERS. [5856.]--QUILTING.-I want to quilt some large articles, such as bed quilts, &c., and find great difficulty in getting the material under the arm of my machine, a "C" of Howe's, which is too heavy, and yet the arm not long enough. Is there a machine for the purpose; or what machine do quilt manufacturers use ?-A SUBSCRIBER'S WIFE. much indebted. It is there stated the ebonite tube for secondary coil should be 18in. long, with disc of ebonite at 8in. from each end, leaving Sin. clear. Having drawn it off to scale, preparatory to constructing a coil to that dimension, I find, allowing in. each for the discs, I have just 11in. for secondary. I find the rings of fin., 1-26in., will take just about 6 to the inch, making 11 x 6 together with the thin discs of No. 28 B.W.G., say about to be some error in the length or the number of discs. =66 discs, instead of 99, as recommended. There appears Would "Inductorium" also favour me with his opinion on the following ?-I have a coil with about three miles of silk-covered wire No. 85, and the primary, abont 716. of No. 9 B.W.G., which I purpose to take abroad, and use in the construction of one such as recommended by him, adding thereto, as per quantities given. The prí mary is wound by hand-that is, the wire is thus insulated instead of being wound with cotton in a lathe-with narrow silk ribbon; on the horizontal plan, the condenser, about 60 in series 7 x 9, insulated by cartridge paper soaked in paraffine, and also a sheet of thin gutta-percha between every layer.-VEGA. [5860.]-YELK OF EGGS.-Will any of your numerous correspondents inform me of the constituent parts of the yelk of eggs, and how best to make a composition possessing the same properties, and the cost of it either by weight or measure ?-JOHN BAILES. [5861.] COMPENSATION BALANCE.-I beg to tender my best thanks to "Seconds Practical Watchmaker" for the very lucid manzer in which he has affected by atmospheric changes of temperature, and not auswered my inquiry. I was thinking how comparatively so thick a substance as the balance should be so easily the thin spring supporting it. I have a plate lever watch with a gold balance, made by an eminent London maker, it varies with the temperature, and I am fearful (even if it were not so expensive) to change the balance for a compensated one, supposing there may be some difference in construction, or preparation, of the other parts of the watch required. Perhaps I may again trespass on "Seconds Practical Watchinaker's" kindness to inform me if my fears are groundless? also if a compensation balance, all of which are made I should suppose according to rule, to approach correct adjustment as nearly as possible, might be put on with advantage without undergoing the more elaborate and expensive process of adjusting? A mere balance of itself could not be very costly, and it would not le required for extreme temperatures.-EcONOMY. [5862.]-GROVE'S BATTERY.-I wish to add strength to the platinum, and think of mounting it in an ebonite slate is secured in a frame, but before doing so wish to frame cemented with shellac, in the same way that a ask whether there is any better method, as platinum is too expensive a metal to play with.-M. [5863.]-LOOKING-GLASS.-Can any correspondent inform me of a cheap method of filling up scratches on the quicksilver side of a large looking-glass ?-G. H. S. [5864]-WATER POWER.-Can one of your correpondents oblige me by stating if I can obtain sufficient power from a turbine attached to a fin. water pipe at a pressure of 15lb. to the inch, to work a small grinding lathe or a 6in. fan ?—J. H. G. [5865.]-SULPHURIC ACID.-Would some correspondent let me know if the sulphuric acid sold at the druggists, for two or three pence a pound, is good enough for those purposes that require a tolerably pure acid? Also if methylated spirit called finish will do for making ether, chloroforin,J&c. ?-J. W. [5866.]-MODEL PADDLE STEAMERS.-Will any fellow-reader oblige by giving directions how to make clock-work motion for model paddle steamers of from 2ft. to 4ft. in length? An illustrated description would be a great favour.-POOR WELSHMAN. [5867.]-MOUNTING SPECULA. I have a bin. speculum, 5ft. focus, which I wish to mount on the Herschelian principle. Will one of my brother readers (perhaps Mr. Newten) kindly help me by informing me at diameter of tube required? A slight sketch would be what angle I am to place the mirror, also the length and very acceptable (showing the position of the eyetube, &c.) if it is not asking too much.-SILENT. [58CS.]-THE SUN'S RAYS.-May I solicit the kindness of our valued friend "F.R.A.S," or Mr. Proctor, to answer the following query? What causes the great divergence of the sun's rays after passing through an opening in the clouds, or even through an opening (devoid of glass) into a large building? It seems strange that the divergence should be so great in the rays of a luminary 90,000,000 of miles distant,-not that I call in question the facts of astronomers as to the distance, &c., of the heavenly bodies, but the above I cannot satisfactorily account for.-BETA. [5857.]-WATER WHEEL-Wishing to attach water- [5869.]-WIRE ROPE.-Will any of your practical correspondents kindly inform an old subscriber whether in. galvanized iron rope will withstand breaking with a ton dead weight at 1,200 yards distance? I want it for [5828.]-MICROSCOPIC.—If “Chase" will re-read my reply (No. 5566), he will see that I proceeded on the assumption that his microscope was, as he himself described it, a £5 instrument, and that its highest power was in. I stated then that I was afraid to guess its magnifying power. Now I am still more unable to do "Chase" says his lens is about 1-16in. Does he mean 1-12in. or 1-20in.? What is the length of his micro-brick oven to an iron one, but I confess that my stupi scope tabe; what eye-piece does he use; who is the maker of his objective; is it an achromatic combination; if so, what is its angle of aperture? These are a few of the queries "Chase" must answer before I can attempt to give another guess at the power of his lens, which, if an achromatic 1-16in. objective of even decent performance, is miraculously cheap. I must apologize for the space this reply to so vague a question vccupies.-H. Ŝ. H. [58411-SPEAKING TUBES.-"Nab's" plan will answer all he anticipates.-H. E. M. [5841.]-SPEAKING TUBES.-In answer to "Nab," I recently had fitted up a tube of which the total length was about 90ft. It was of the hard brown rubber, lin. diameter inside, and had half a dozen sharp elbow bends in it. It was perfectly satisfactory. I do not suppose that an extra 10ft. or 20ft. would make any appreciable difference in the distinctness of sound or articulations. -W: L. [5858.]-GLASS BURNING.-If "Kemp" has succeeded in constructing a kiln from the directions given at p. 476, 4823, Vol. XI., will he kindly give a rough working diagram of it? I much prefer the operation of a dity is too great to conquer this description. I am already much indebted to Mr. D. F. Ashton, but I ventured to make a final appeal to him in my letter, p. 64. let. 513, Vol. XII., but without success. All the difficulties therein mentioned no longer present themselves, save the brick furnace. Will Kemp" or some brother reader help me in this, and also tell me what fuel is best, and where the earthen-pan is to be obtained? I have [5874.]-CHARCOAL.-Would some of your readers burnt some enamelled glass in a crucible in quicklime kindly inform me the best method of extinguishing to try the colours, and have succeeded perfectly in pre-wood charcoal from the retorts to prevent it igniting paring them. All I now want is to construct an earthen without renewed fire? Also the way it is ground for kiln to vitrify the pigments on the window glass. I urge foundry purposes; end if any danger connected with the the motto at the head of my instructions on "Dissolving grinding, what means taken to prevent it? InformaView Painting," and as I am at all times ready to lend ation on this subject would much oblige.-JUVENILE helping hand to the best of my ability, I do hope some CHEMIST. one will do the like by-SABLE. (5859.)-COIL-TO "INDUCTORIUM."-May I be allowed to ask "Inductorium" a question with respect to his coil, given August 5th, p. 472, for which we are body" inform me how to spring a lever watch in the easiest manner?-LEARNER. [5876.]-INTENSITY COIL.-Can any one inform me of back numbers containing information of an easy method of making a small coil, say for 4 half-pint Smee's batteries; also cost of materials for the same, and oblige-BEN. G. [5877.]-COLOURED LETTERS.-Can any reader tell me how the colours are mixed for painting large block letters in colours, so that when rubbed with size they will not run as when painted with water colour? I want red and blue for large texts.-M. DUFFY. [5878.]-BOOK-BINDING.-How is the sewing part of binding done; how are the numbers of a book threaded together; are there two threads worked at the one time ?-M. DUFFY. [5893.]-FASTENING MARBLE SLAB.-Will some [5894.]-FREEZING APPARATUS.-A machine, of [5879.]-WATER POWER.-I have a supply of water through a fin. pipe, with a head of 800ft. supplied to my-BLUE DYE. door with a 3in main; what power could I obtain from this, andwhat is the best means of applying it, a turbine or awater wheel. ?—Aqua. [5880.]-MAGIC-LANTERN AS A PHOTOGRAPHIC ENLARGING APPARATUS. - Is this practicable? With my lantern lenses, by fixing them in a dark box, and placing the negatives two or three inches in front, I can get a much enlarged image on the ground glass at a distance of about 2ft., but it is not clear and sharp; and if a strong light shines through the negative, the picture is all the colours of the rainbow. Will some one be good enough to say whether the magic-lantern lenses can be used for this purpose; and, if so, how can I remedy my defects ?-CAMERA. [5881.]-CHLORATE OF POTASH.-Will any of your correspondents who have had practical experience in the manufacture of KO CIOs, kindly give an account of the process, describing the plant required for making, say two tons weekly, and relative quantities of raw material required, viz., CaO MnOg, and KC1?-R. H. D. [5882.]-BLACK BRONZE.-Will any reader of the MECHANIC be so good as give me a recipe for bronzing brass articles black, and how to apply it ?-GALA. one ac [5883.]-COTTON SPINNING.-Will some quainted with cotton spinning give a good recipe for varnishing top leather rollers, one that would last moderately and work smooth, so that the fibres of cotton in passing through the rollers will not take up so much ?-CARLTON. [5884.]-EXAMINATIONS FOR SURGEONS.-Will any obliging reader answer the following: What are the subjects for the preliminary examination for a surgeon? -YOUNG MAN. B [5885.]-CISTERN.-If the cistern A, B, C, D. 12ft. deep, be kept constantly filled with water, and two pipes, E e, and Ff, of the same diameter, be fixed in the bottom of the cistern, so that the top of the pipe, E, e, will stand 2ft. above the bottom of the cistern, and the top of the pipe, Ff, will stand 8ft. above the bottom of the cistern, which of the pipes, E e or FJ, will discharge the greatest quantity of water in a given time at the common level, e, ƒ?—Q. D [5886.]-VICE BENCH.-Would you allow me to ask "J. K. P.," through the medium of the ENGLISH MECHANIC, if he would be kind enough to send a drawing of a vice bench (one that can be made by an amateur) of wood if possible ?-H. E. [5887.]-ELECTRICAL QUERIES. THE SULPHATE OF MERCURY CELL.-1. If I heat 1lb. of mercury and 31b. of sulphuric acid in an evaporating dish how much of the sulphate will it make, and what temperature is required? 2. If I connect the wires of a sulphate of mercury cell, and let it work to exhaustion, would the whole of the mercury that was contained in the sulphate be deposited at the bottom, and what becomes of the sulphate of zinc (I suppose it is) from the zinc plate? 3. Can I re-form the mercury into the sulphate again without much trouble by the process in my first query, and if so I suppose I should have my battery kept working as cheaply as any form of battery, notwithstanding the expensive nature of the materials at the onset?-COLONEL B. [5888.]-HARMONIUM STOP ACTION.- Will our kind and valuable friend "Adept " do me the favour of informing me of the simplest and most effective stop action for an ordinary harmonium of two and a half rows of reeds; also the mechanism required for a grand jeu at knee or for stop.-EVERETT. [5889.]-BOLOGNA SAUSAGES.-How can I make the colouring for staining the skins of Bologna sausages a good red ?-MIMIMUS. [5890.]-MANDREL FOR WATCHWORK.-I shall be obliged if any of your correspondents would kindly give a description, and, if possible, a sketch of the best description of Swiss or English mandrel for watch work, with slide rest.-T. E. FREEMAN. [5891.]-VENUS AND THE SUN.-Will "F.R.A.S." kindly inform me how near he or any other observer has seen Venus to the sun's disc, especially if within the corona-of course I do not mean during her transit; also if the illuminated disc of the planet was darker or brighter than the background against which she was projected; and if the planet was darker, if he can suggest the probable cause of the superior brightness of the background? I would also ask if that portion of the planet's disc which is not illuminated by the direct rays of the sun becomes visible when she is very near this dise? My reason for troubling "F.R.A.S." for these questions is, that I think his replies may enable me to conceive a probable cause for the zodiacal light. IGNORAMUS. [5892.]-SOLAR LAMP.-Perhaps you or some of the readers of your journal will be able to give me a clear pefinition of a solar lamp, and also of a solar argand lamp. I have a large powerful magic lantern for which I want to procure a good bright light. I have heard of the above-mentioned lamps, but do not know what they are like, and cannot obtain any information concerning them in the place where I am now living. I should therefore be very much obliged to you or any of the readers of your paper for any information on the subject. I am, and have been for some time, a constant reader of the ENGLISH MECHANIC.-G. B. fellow reader, practically acquainted with the subject, RINGING.-Will some one be kind enough to say what [5900.]-ATMOSPHERE.-Will any of your scientific [5901.]-MEDALLET.-I have a medallet, or token, [5903.]-SULPHATE OF MERCURY CELL. - In -W. C. C. [5904.]-MECHANICAL MOVEMENTS.-Would any kind subscriber say whether C. Parson's patent, described in the "Mechanical Movements," No. 194, p. 365, Vol. XI. ENGLISH MECHANIC, is expired or not?-EKLOM. STEPANFETCHIT. [5913.]-MICROSCOPIC.-Will some corresponder Inform me of the proper diameter of lin. in., and fin should be set to form a compound objective for the mi focus achromatic lens; also, the right distance ther croscope?-GOLDSMITH. chemical correspondents inform me of a delicate text [5915.]-ARTIFICIAL IVORY.-Could any one tell me how to make some kind of artificial ivory for harmonium keys ?-IVORY. USEFUL AND SCIENTIFIC NOTES. SEWING MACHINE CONTESTS.-At the Workmen' International Exhibition, lately brought to a close at th Agricultural Hall, nearly fifty sewing machines wer exhibited, noticeable for invention, improvement, some for strict imitation of Howe's, Wheeler & Wilson's of George-street, Blackfriar's-road, London. 5. Second awarded as follows:-1. First Class: H. Cyrus Symons Singer's, and Thomas's machines. The prizes wez: class: Messrs. Judkins and Edward Ward, London: Arthur J. Maxfield, Birmingham; Wm. Taylor, Great Driffield; Westmoreland Brothers, Nottingham. chine, advertised as the "A. B. C.," Machine, " nings, for imitations of the new "Singer" Family Ma Third Class: Messrs. John A. Blacklock; George Jer latest American Wonder;" A. Clegg, of Finsbury, fe the Elliptic Hook Machine; John Asten, Colchester; J. W. Connor, Maidstone. A NEW GUN.-There is in the course of erection, is the east side of New York Bay, a gun that will throw 800 five ounce balls in one minute, to a distance of abor two miles. The shot may be either red-hot or cold. The gun is circular, and appears like two discs of heavy ire plate, about 4ft. in diameter. Upon one side is a fanzel to convey the balls through to the proper chambe without cessation of firing or diminution of speed. Thi muzzle projects upon the periphery of the circular ma chine, and may be elevated or depressed at the will e guns may be worked by steam power or manual labour the gunner, by the trunnion upon which it rotates. The if by the former, it will throw from five ounce balls eight-pound shot and shell, thus making it a destructive implement of warfare. 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 wi look over the list, and send what information they can for the benefit of their fellow-contributors. Since our last "Eklom" has answered 5003; "Wire." 5087;," Muzzle-loader," 5086; "An Engraver," 36 "Sergius" 5233. 5240 Refrigeration, p. 119. if for distance of hammer-stroke two-fifteenths and a estate-plans, &c., &c., to colour, and am desirous of [5908.]-THERMOMETER.-Will any of your corre- [5909.]-STEREOTYPING.-Would "Leeds" or any the result.-PATER. kindly inform me what the lithographic varnish is used [5912.]-TO MILLERS.-Can any reader throw any 5246 5247 Mounting Buterflies' Tongues, 119. 5248 The Ripening of Pears, 119. 5249 Pattern on Linen, 119. Brewer's Truck, 119. 5258 Wire Drawing, 119. 5262 Size and Power of Boiler, 119. 5269 The Manganese Battery, 120, 5270 Enlarging Photographs, 120. 5278 5282 Paper Foliage, 120. 5283 Verge Escapement, 120. 5285 Splitting Selenite, 120. 5290 Damaged Barometer, 120, 5292 Percussion Action for Barometer, 120. 5293 Cement for Leather, 120. 5298 Glue, 142. 5299 Large Induction Coil, 142. 5306 5304 Photo-Reliefs, 142. Flexible Writing Slates, 142. 5307 Black Japan, 142. 5309 Carriage Painting, 143. 5811 Shrinkage of Type from overheating in Stere typing, 142. 5313 Power of Engine, 143. 5319 Chemical and Brewing, 143. 5321 Dressing Millstones with Diamond or "Bort," 1 5324 Removing Paiut and Tar, 148. 5335 Soldering Brass Tubes, 143. 5937 Filtration, 143. Silvering Specula, 143. Dry Colours, 143. 5342 5344 Silvering Process, 143. 5460 Teeth of Wheels, 143. 5362 5361 5370 Hot-air v. Steam-engines, 144. 5374 Counterpoint, 144. 5379 Wine in a Glass, 144. |