you will require balance-block, as in Fig. 2. A is crank; B, two boards, one on each side of crank, with weight; D, placed between to balance the other FIG. I B crank; CCCC are the bolts to fasten together. Any other information I shall be glad to give.C. L. [33917.] Burning Sawdust. In reply to "A. W.," the writer does not know what plan they adopt in saw-mills. Probably, they carelessly throw it on to the fire, without rhyme or reason as to how it is to unite with oxygen-that is, the carburetted hydrogen gas of the sawdust with the air. The tendency is to deaden the fire by present plan or "A. W.'s" plan. If "A. W." will close his ash-pit door and supply a draught from underneath, and regulate that draught with a valve, he will not only burn all his sawdust and get a bright fire, but he will be able to regulate his oxygen as the fire requires it, and will considerably economise his fuel-that is, by consuming it to its utmost.-J. D. CURTIS. [33918.)-Leather Suction Hose-Is riveted by hand. The covering for the wire is oiled canvas, and cemented with indiarubber cement. The cone is less by about one-eighth of the diameter of the pipe, and merely pushed in the lappel with wire afterwards.-W. W. [33919.]-Bize of Battery for Electro-Metallurgy. A form of battery I have found to deposit copper and silver in the most satisfactory manner is as follows:-Provide a cylindrical stone jar, A, capable of holding two or four gallons; inside the jar is fitted a cylinder of sheet copper, B-1-64th of an inch in thickness is sufficient-to this attach binding screw, C. Within the copper cylinder place a porous cell, D, and suspend in it (by means of wooden cover, B A [33925.]-Building Societies.-As I have stated before in these pages that the best investment one can make is to buy a house and live in it himself, so I have a fellow interest with "Jib" concerning the morale or profit of building societies. But I also am astonished at the increase and get up of them, the directors. &c., being men of so low a status in the community that they could hardly afford the dignity consequent on such an elevation, yet they manage somehow. I'll tell you: Suppose I want to buy a house. I go to the secretary (that most important individual), and receive this advice: -"Borrow £360 on six shares, 1s. fee on each share; repay. ments extend 14 years at £3 1s. a month-viz., £36 12s. per annum; with fee, £36 188.; total, £511 128., leaving out cost of conveyance," &c. So the society gets £151, or 11 per cent. per annum profit on the transaction, but only pays the shareholders 5 or 6 for the use of their money. The expenses buy a country house or two for somebody else! Well, they seem to thrive very well indeed, but what profit does the buyer get? The society won't lend on the full value, so the house must be of £450 value. That is the security. Buyer has to provide £90 (to make up purchase money), which added to total cost as above is £601 12s., without cost of conveyance, ground rent at perhaps £4 103. a year, repairs, &c., &c. I know the grand total will be yearly rental to pay for the house. Now, notwith£700. This at 5 per cent. is £35 a year, or a good standing the house being the buyer's property I fail to see the advantage, because the house will deteriorate in value as the lease becomes shorter, and he will have paid £250 more than it is worth, besides paying about £50 per annum instead of £35, or about £210 difference between tenant and lessor's expenses. Suppose, then, he rents the house at £35 instead of buying it, and saves this £210 in 14 years, then adds the £90 he had to make up, reckon the cost of ground rent £63, and he has the £360 pounds in hand without counting repairs and other expenses, which I am sure would make up to the prime price of £450. I think I am right in saying that the man who saves is better than the man who borrows, because he can get interest for his money, and can buy what he wants without paying too much for it. If our mechanics only knew the value of a pound they'd never part with their money carelessly. If a man buys a house with ready money he may count on 11 per cent. sure, but if he borrows it he will lose from 15 to 20 per cent.-FIDdler. E) a zinc rod, F. Fill the stone jar with a mixture of (in proportion) water, 1 gallon; sulphuric acid, lb; nitric acid, oz., and fill the porous cell with a saturated solution of common salt, acidulated with a few drops of muriatic acid. A compound battery, Constructed in this manner, I have found will deposit copper in abundance from a solution of the sulphate. The battery retains its action for a long time, and the deposit is very even. - ACIDUM ACETICUM. [33920.1-Furniture Cream.-Derby Cream is made by adding 6oz. of linseed oil to 3oz. of acetic acid. This is agitated well, and oz. of butter of antimony and 3oz. of methylated spirit added to it. -THE OLD GENTLEMAN. petroleum is to have attached thereto a label in con. spicuous characters stating the description of the petroleum, with the addition of the words 'highly inflammable,' and with the addition, in the case of a vessel kept, the name of the consignor or owner. If sent or conveyed the name and address of the vendor." Penalty for non-compliance with the Act, £5 for each offence, and the petroleum vessel to be forfeited. Petroleum is not to be kept except in pur suance of a license by the local authority (in large quantities). The charge for such license should not exceed five shillings. In case of refusal of license by the local authority the applicant may demand a cer tificate of the grounds of refusal, and may memorialise the Secretary of State, or if in Ireland the Lord-Lieutenant.-C. G. [33927.]-Money Lenders. Until 1854 no higher rate of interest on loans could be enforced than 5 per cent., but in that year, by the Act 17 and 18 Victoria, chap. 90, it was enacted that any rate of interest agreed upon between lender and borrower should be legally recoverable. The Court of Chancery has, however, interfered under special circumstances, but these would probably not affect " Jib." In the United States the maximum interest to be paid in each State is defined by law. A bill of sale should either provide for the immediate acquisition of the goods which it covers, by the acceptor, or it should be at once registered. Otherwise, it is presumptive evidence of fraud; but when the bill is accepted as a mortgage in default of payment of a debt, fraud will not be presumed. By 29 and 30 Vict., cap. 98, a bill of sale must be renewed every five years, or the security becomes valueless.-C. G. [33920.1-Furniture Cream.-Soft water, a gallon; soap, 40z; beeswax in shavings, llb. Boil together, and add 2oz. of pearlash. To be diluted with water, laid on with a paint-brush, and polished off with a hard brush or cloth. 2. Wax, 3oz.; pearlash, 2oz.; water, 6oz. Heat together, and add 4oz. of boiled oil and 5oz. spirits of turpentine. 3. The name is sometimes given to a mixture of loz. white or yellow wax with 4 of oil of turpentine. (From Beasley.)-D. STRATHERN, Medical Student. [33920.]-Derby Cream or Furniture Polish. The following recipe we have used with great success:-Rain-water, 1 gill; spirits of wine, 1 gill; beeswax, loz.; pale yellow soap, loz. Cut the wax and soap into thin slices, and boil them in the rainwater until dissolved. Take off the fire, and occasionally stir till cold. Aftewards add spirits of wine, bottle, and it is ready for use. The above compound should be applied with a piece of flannel, and afterwards rubbed with a soft cotton cloth. W. H. ROBINSON. [33931.]-Mercuric Ethide.-"H. T." should certainly not venture to make this, as it is intensely poisonous.-F. WOODMAN, [33940.]-Rotary Pump. -I am afraid that W. H. Ottewill, and possibly others, have been misled by my answer. I did not mean to imply that the Greindle pump was the "simplest and perhaps most effective" of pumps in general, but merely of the class inquired about. As a fact, I should not recom mend a rotary pump of any kind except for special purposes-e.g., where a large volume of water had to be lifted in a short time to a low height. The details of this pump as now sold are considerably modified. Information may be had in Goodeve's Principles of Mechanics" (not very much), Reuleaux's" Kineof Machinery," section" Pumps."-JAN. matics of Machinery," and Applebey's "Handbook of all the copyhold lands of his manor, and in the [33933.]-Copyholds.-The lord is actually seised case mentioned retains the freehold, and not a mere seignory. Such being the case, the words "grant seisin" in the admittance, so far as the relations between the lord and the tenant are concerned, means [33945.]-Pythagorean Theorem.-The follow ing proof occurs in the writings of the Chinese Bages:-Let ABC be any rectangular triangle: EFA C. Rotate A E B F round E till B on B C construct square. B C D E, and draw grant possession." But with regard to other copyholders, the tenant admitted will stand in a position exactly corresponding to that of a man seised of an estate in freehold. Should "Student" require further information, I shall be glad to help him as far as I am able,-BUTTERFLY. [33936.] Petroleum.-Petroleum cannot be stored without a license, and the penalty is £20 for each day, unless it is kept in separate glass, earthenware, or metal vessels, containing not more than 1 pint each, and the aggregate not to exceed three gallons. The Act now in force regulating the storing and use of petroleum is that of the 21st August, 1871, 34 and 35 Vict., cap. cv.-T. E. J. B B falls on D and F on G. Similarly rotate ▲ ABC round C till B falls on D and A on H. The hexagon, EFACHGE, is obviously =square A C + square A B, and shows how to decompose the latter two squares as required by "Autos."-LEIDHOLD. [33945.1-Pythagorean Theorem.-This is done by dropping a perpendicular from the point, C, on the line, A B, the hypothenuse of the right-angle triangle D, from D parallel to the line, A C, which is equal to the line, AC, the side of the small square All other lines are drawn parallel to the sides of the squares, as seen in the diagram.-AULD REEKIE. [33948.]-Lawn Tennis.-Ashes would not make a good tennis court, they retain the damp, and would require rolling after each heavy rain. Small pieces [33936.]-Petroleum.-As to the storage of petro- of red sandstone ground into powder are very good. leam by the 34 and 35 Vic., cap. 105 (Petroleum Act,-THE OLD GENTLEMAN. 1871), it is enacted that the name "petroleum shall include any rock oil, Rangoon oil, Burmah oil, oil made from coal, schist, shale, peat, or other bituminous substances, and any product of petroleum or of the above-mentioned oils, and such of the petroleum so defined as when tested gives off an inflammable vapour at less than 100 degrees Fahrenheit:-" When any petroleum is kept at any place, except during the seven days after it has been im ported, or is sent or conveyed by land or water between any two places in the United Kingdom, or is sold or exposed for sale, the vessel containing such [33951.]-Repairing Leaky Water Pillow If there are many leaks in this it would be cheapest to buy a new one. Two or three leaks may be re paired, to answer for a time, as follows: Coat a thin piece of calico, sufficient size to make patches for leaky places in pillow, with three coats of Para solution. The Para rubber can either be dissolved in mineral naphtha or turpentine; if the latter, the solution requires more time for drying. The first coat must be put on thin, and time allowed for drying between each coat. Next, see that the pillow is perfectly dry and clean, then rough the surface of rubber a little where leaks are. This is to make solution stick. Coat round the cracks with two or more coats of solution, just according to consistency of solution, patting first coat on thin, and rubbing well in with the finger. When sufficient solution is on and dry, you can put the patches from calico on, press well to water pillow, and do not use for a day or two after repairs. Cracks in tabing cannot be repaired for lasting, as the rubber when cracked is perished, and gone hard on the surface. You may fill the cracks up with solution; and join edges together when dry, but it is scarcely worth the trouble unless tubing is large.-NEGROHEAD. [33953.)-Magnetising.-Place the magnets on a board parallel to each other, and at a distance apart equal to the space between the poles of your horseshoe magnet. Across the ends of the magnets place two bits of soft iron, so as to form a rectangle. Secure this to the board. Then place the large magnet so that its poles rest one on each magnet near the ends, and draw it slowly along to the other end. Then lift it off, and return to the other end, and repeat the process many times, occasionally rolling the magnets over.-J. E. FLOYD. [33968.J-Cryolite and Rutelite. Cryolite (Greek-zpúos, ice, 2.0os, stone) is a rare mineral from Greenland. It is a double fluoride of sodium and alaminium. It readily fuses in the flame of a candle. whence its name. Rutelite (Latin-ratilus, red) is native oxide of titanium, which metal is found in Cornwall. The peroxide or titanic acid exists nearly pare in titanite, or ratelite. I do not know to what purposes either of these minerals are applied.-F. C. HAWKS. [34015.]-Paste-Let "An Old Literary Man's make his own paste. If it is not stickable it will be his own fault. A teaspoonful of brown sugar might improve it in this respect. To a pint or a pint and a half of paste add sufficient corrosive sublimate (a virulent poison) to cover the point of a penknife, and to improve its smell a few drops of oil of lavender. Such a paste will keep for weeks, even in the hottest weather-in fact, until it dries up. Proved over and over again. Will the querist let me hear how he likes it ?-ARCANUM. [34021.]-Phonograph.-After the number of failures that have been recorded it is quite refreshing to hear of your success. Adjustment of the points, without looking at them, is simply a matter of practice. My method is to screw up the nut slowly with one hand, while with the other I move the handle backwards and forwards about a quarter of a turn; I can tell by the sound of the scratch when the adjustment is right. Of course it is easy to add regulating stops, but they will be found to require frequent alteration, as the instru ment is very sensitive to changes of temperature and moisture.-SHELFORD BIDwell. [34025.]-Goldfinches.-The top of the head in a [33968.]-Cryolite.-Cryolite is the only mineral [33980.)-Brine. There used to be some at Lymington, Hants; but I do not know if they exist at present.-TELESCOPE TELE. [33995]-Cement for Cast-Iron Cisterns.weather.-W. J. CHADWICK. From much experience I can recommend the following:-Sal-ammoniac, 2 parts; flowers of sulphur, part; iron filings (fine), 200 parts; to be made into a paste with water. It requires some time to set-say, a couple of days.-W. J. CHADWICK. [33996.]-Locomotive Regulators.-The ad vantage is simply a matter of opinion-I might say s difference of opinion. Some engineers prefer to take their steam from the top of a dome, because they say it is drier; others will not have a dome, and say they can get the steam as dry or dry enough without; and when there is no dome the smoke-box end is certainly the best, for many reasons.-W. J. CHADWICK. [33998]-Slide-Rest Castings.-I think that "Lathey" would do better to have his castings planed; he would get them done for a few shillings, and save his time, and produce a better job than might be expected with a file. A slide-rest, to be any use, should be a good job.-W. J. CHADWICK. (34001.]-Phonograph.-Tin plate is not a suitable material for the diaphragm. If tinfoil is used for soldering, it is unnecessary to use sufficient heat to blister a ferrotype. A soft point will very quickly wear too blunt to be of any use. Stout writing paper or vegetable parchment, would make a better diaparagm than animal parchment. Thin tinfoil is altother useless. The Editor would properly refuse to give the makers of whom I purchase a gratuitous advertisement, but if you will advertise your address I will send you theirs. See also reply 33688.SHELFORD BIDWELL. [34002.]-Magnetic Engine.-Undoubtedly a machine of h. p. could be made; but whether its weight with accompanying battery and liquids would be suitable, I cannot say. I really cannot supply the information required. I should look for a handsome fee if I worked it out professionally, seeing that to be of any use it would involve several days of research and calculations. Therefore, it is pretty clear that such information cannot be reasonably expected in these replies.-SIGMA. 34011.]-Photography.-If "G. B. S." has gone through Photography Made Easy" he should be able to know a negative when he sees one; and my advice is to get a dozen Swan's & plates for 3s, and develop them as per instructions, with the ferrous oralate to develop-this is photography made easier. The plates must be carried by extra dark slides, or s changing box and special dark slide.-W. J. CHAD WICK. QUERIES. [34031.]-Stamping and Punching Press. Will some one show by sketch a press for punching holes and stamping small articles of iron, as bicycle stampings are done? Would one like those small presses to be seen in Birmingham tool-shops do, but larger? I can make it myself, having the tools.-IRON. tute. Will any reader give the specification of the [31032.]-Organ at Bow and Bromley Instiorgan at the Bow and Bromley Institute P-MUSICIAN. [34033.]-Powerful Telephone.-I wish to make a pair of telephones, as powerful as possible, so as to be of use at somewhat noisy entertainments? Is the horseshoe magnet box telephone more powerful than the ordithere any advantage in making the ordinary form larger nary form, and, if so, what arrangement is the best? Is than usual ?-J. E. F. readers kindly inform me how to produce, on polished tell me how to glaze bricks white ?-J. W. S. [34036.]-Electrical.-I have a glass cylinder, 7in. x 1lin., for an electrical machine. Will some one inform necks, which are 2in. diameter ? Also the method of fixme how to mount it-if cork or wood is best to stop the ing the cushion or rubber on to the stand, so as to press on to the cylinder and be easily removed.-AMATEUR, Derby. small gas engine to drive my lathe. Will some one tell me [34037.]-Small Gas Engine.-I want to make a where I could get drawings or a practical work on the Otto silent engine? Any information as to size of cylinder, &c., will oblige-AMATEUR, Derby. [34038.]-Curing Rubber with Bisulphide of Carbon.-Can any of "ours" instruct me how to cure indiarabber with the above for small goods ?-YOUNG MECHANIC. how fruits are preserved whole, such as we see in grocer's [34039.]-Preserved Fruits.-Can any one tell me shops at Christinas time, and how long will they keep ?PLUM. [34040.]-Domestic Fire-Engine.-I shall feel obliged if some of your readers will give their opinion as to the most efficient and powerful portable fire-engine for dwelling-houses (with staircases and passages of the average width), and of the quantity of water such engines throw per minute? Also if there is any solution that could be added to the water (such as alum) in order to extinguish a fire more rapidly than with water alone.— INQUIRER. [34041.]-G.N. Engines.-Will any correspondent kindly give particulars as to G. N. express engines in use about 1857? Old No. 94 class, I mean, which ran all main line express and fast trains, and were timed at 48 miles an hour. I shall be obliged especially for dimensions of cylinders, diameter of driving wheels, maker's name, &c. [34029]-Seeing Under Water.-F. Galton, Esq., F.R.S., in the 5th edition of "The Art of Travel," page 87, mentioned that he read a paper on water spectacles at the British Association in 1865. I copy the following from the above-mentioned book" If the spectacle lens be of flint glass, and doubly convex, each of its faces should have a curvature of not greater than 6-tenths of an inch, nor more than 8-tenths of an inch in radius. Within these limits it is practicable to obtain perfectly dis-N. Z. tinct vision under water by pressing the spectacles forwards or backwards to a moderate degree. [34042.]-G. E. Engines.-Although the old G. E. I have tried, but hitherto without much success, to time ago, I should be glad to know their chief dimensions express engines of the 97-102 class were broken up some arrange the fittings by which the lenses are secured,e.g., cylinders and driving wheels, &., as they were so that by a movement of the jaw, or by an eleva- very fine engines of their day, if not the finest narrowtion of the eyebrows, I could give the necessary gauge engines of that time. I understood that their adjustment of the glasses, leaving my hands free for cylinders were 17 x 24, drivers 7ft. Is this so P-N. Z. the purpose of swimming."-G. W. B. UNANSWERED QUERIES. The numbers and titles of queries which remain unan- [31043.]-G.W. Express in 1848.-Some of your correspondents have mentioned the fast times of the G.W. time tables in 1848.51. Can they give the times of (1) leaving Paddington; (2) Didcot, arrive and depart; (3) Swindon, arrive and depart; (4) Bristol, arrive and depart; (5) Exeter, arrive and depart; (6) Oxford and Birmingham, arrive and depart; the object being to compare with present work ?-N. Z. [34044.]-Mineralogy.-I have a small collection of minerals. Can any one tell me of a good system by which to arrange them, also name of book explaining such system? One mineral bears the name " Alophane." What is this ?—HEREWARD. [34045.]-Fishing Boat.-I intend building a boat for fishing purposes, 24ft. keel, 8ft. beam, and 4ft. from top of keel to top of gunwale. If I lay an air-tight deck from stem to stern (so as to enclose about 108 cubic feet, Since our last "Telescope Tele" has replied to 33382 including ballast, in the bottom, equal to 3 tons of water), 33536. 33350. Copper Smelting, p. 430. 33357. Tanning, 430. 33373. Bleaching Guttapercha, 430. 33381. Making Bicycle Wheel Rigid, 430. 33383. Roller Bearings, 430. 33401. Music, 431. 33405. Chinese, 431. 33407. L. and N. W. Engines, 431. 83597. Australia or New Zealand, p. 534. 33608. 33618. Collodion, 535. Legal, 535. 33619. Gramme Machine, 535. Designing, 535. 33624. 33626. Bichromate Cell, 535. and place valves in same, will she be able to carry 2 tons without sinking, and clear herself of water? A drawing of the best valves and probable cost and how to place them to be of most service in a fishing boat will obligeGLASGOW. [34046.]-Bicycle.-The rim of the front wheel of my bicycle has got bent in two places, so that the rim comes very near to one of the forks. The bicycle is a 48in. "Ariel," so I have no control over the wheel by means of screws at the centre. I have tried hammering the rim on a concave block of iron, but with no effect. I also tried holding the rim in two places firmly in vices and wrenching it with as little success. I want, to know if there is any other way I can try, and better still, is there any arrangement by which I could have screws at four places of the nave so as to get control of the rim ?-R. W. RUSSELL. [34047.]-Hardening Buff Leather for Carving.-I am in the habit of using patent graining leathers made thus-Piece of buff leather 18in. long, 5in. wide, and in. thick, is carved to imitate the grain of the wood that has to be represented, the carving being only the depth of 1-16th of an inch, leaving the reverse side perfectly clear. It is necessary that the leather to be carved should be hardened with some preparation that will make it almost as hard as wood but not permanently so, as it is absolutely necessary that the preparation should be got out again when the carving is finished, and the leather rendered as porous as before. As the leather is only used for graining in water-colours the preparation 33649. Drilling up Staff and Pinions for New Pivot, must not be of a greasy nature, as that would render the 536. 33650. Willow Boxes, 536. 33655. Pickers, 586. 33658. Stand for Harp, E86. Chlorhydric, 536. leather entirely useless. Can any of your readers inform me of anything that will harden the leather in the manner required?-T. B. [34048.]-Fuller's Battery.-How is this battery made ?-FRAS. [34049.]-Crystals in Bath.-What are the silkywhite crystals that form in a new silver bath for negatives, the usual nitric acid, iodide of potassium being added, and then filtered P-G. O. [34050.]-Imitation Freestone.-What is the best way to finish gable of house so as to resemble front, which is freestone ? The stones are flat, but picked or chiselled rough. At present the gable is rough cast, which has peeled off for about a yard at bottom, apparently from damp.-R. J. [34051.]-Hens and Eggs.-Will " Anglo-Dane kindly say how fowls can be profitablly kept without a grass run, and what kind he keeps ?-A. B. R. [34067.]-Injection.-Can any of "ours" give me the [34052.]-Metal Polishing.-Will some practical reader kindly describe the process used in the electroplate trade for removing the scratches and marks in such articles as spoons, forks, &c., previous to their being replated, where steam power is at hand P-MAKEM BRIGHT. [34053.]-Telescope.-I have the front combination [34069.] Galvanometer.-To "SIGMA."-I am of a photographic lens, 3in. in diameter and 20in. focus, about to construct the universal galvanometer described out of which I wish to make a telescope. Will some of by you on page 131-2 of your book. Before doing so I your contributors kindly oblige by telling me how to wish for further information on points I do not thoroughly proceed P-AN OLD FELLOW. understand. The coil I intend making in two parts. 1. [34054.]-Glazed Jars.-How can I find if earthen- How far apart should the coils be ? 2. Should the double ware jars are glazed with lead or otherwise? I have a length of No. 18 wire, 9 turns in each channel, finish in number of them in which I am desirous of preserving the middle or at the sides of the coil ? 3. I have tried in pickles, &c., but am afraid to do so, being uncertain as vain to understand the connections. If you could in any to the material used as glaze.-AN OLD FELLOW, Mel-way make these plain I should esteem it a great favour. bourne, Victoria. AMATEUR. [34055.]-Photographing the Moon.-I have a 4in. refractor, 5ft. focus, and I wish to procure some photographs of the moon and planets. Will some correspondent kindly tell me how to go to work, or refer me to a back number, or a good work upon the subject? I am inexperienced in photography. Is there any chance of my succeeding in getting photographs ?-J. L. [34056.]-Waves of Light and Heat.-Are there any experiments recorded which indicate the amplitude of waves of light or radiant heat? I do not mean their length or period. I noticed in a Dublin newspaper that a paper had been read at the British Association on an experimental means of determining the velocity of radiant heat, but no report of the paper appeared, so far as I have observed. As that is one of the latest contributions to the subject, although not necessarily involving the question of amplitude, it might throw light on it. Have any of your readers heard the paper, or can they refer me to a report of it P-PI SQUARED. [34057.]-Electric Light.-Would Mr. Lancaster kindly answer the following? I wish to know what would be the probable cost of wire, carbon pencils, glass cylinder, best arrangement of carbon pencils, size of wire, &c., to make an electric light suitable for a merchant ship (running at high speed); two lights would be required. Also probable cost of working and keeping up the same, allowing nothing for motive power, which would be derived from the main engines.-RAM CHAND BISWAS. [34058.]-Microscopical Manipulation.-I have an inclination to observe natural objects, and so am led to look to the microscope for assistance, and my object in writing is to ask for the titles of some books, by the study of which I may become indoctrinated in the manipulation of the instrument, as I am afraid that without some guide I should be quite at a loss how to make use of the many appliances that I see noticed in your columns, the perusal of which affords me great pleasure, and makes me wish I was a little nearer to your correspondent "Essex," who, I fancy, would be magnanimous enough to give me the information I want. I fancy that" Brewster" must have published something that would be useful to me, but where I am (in the bush) I have not access to the London catalogue. Something like "Faraday's Chemical Manipulations" would be the thing I want. We are surrounded by multitudes of objects, animate and inanimate, that make one wish to pry into their secrets, but it is little use having an instrument without you have some idea how to use it. We have opticians in Auckland, who, I dare say, would supply the necessary instruments. -THOS. COULTHARD, Awitu, Auckland, N.Z. [34059.]-Bit for Boring Solid Barrels.-Thanks to" J. K. P." for his sketch of rifling machines. Would he be so kind as to state what he thinks the best form of bit for boring solid steel barrels ?-W. W. [34060.]-Surveying.-What books should a beginner study ?-A SUB. [34061.]-Electrotyping Ferns.-Some time ago I saw a basket containing ferns electrotyped in gold and silver. The effect was very fine. I have often wished to be able to imitate those, adding skeleton leaves to the bouquet, but have never met with a description of the process. Would the process described by "Anglo-Dane" (33709) for electrotyping insects suit, or is there a better process?-ZIA. [34062.]-Cementing Cork to Metal and Glass. -How can I fix some strips, Sin. wide, of virgin cork bark on to the zinc frame and glass of an outdoor aquarium, so as to stand firm against wind and rain ?-A YOUNG ME CHANIC. [34063.]-Model Portable Engine.-I have a boiler 26in. over all, barrel 7in. dia., fire-box 10in. square by llin. deep, from bottom of fire-box to top of shell 16in., barrel 14in. long, 9 brass tubes lin, in dia. of ordinary gas-pipe, plates best Lowmoor iron in, thick. Please state what size cylinder the above will drive? Also if tubing is strong enough ?-ONE IN A FIX. [31070.1-A Galvanometer. To "SIGMA."-I have a differential galvanometer by Siemens of the following construction:-Needles astatic, a brass rod rising from the centre of dial for the reception of magnets to reduce the sensitiveness of needles, a pair of coils whose inner ends are joined within the instrument, and whose outer ends lead to terminal screws, FF (see Fig.), outside, insulated from brass case of galvanometer by a piece of F ebonite. On the opposite side, and underneath, there are two brass screws, EE, in the brass bottom of instrument, for securing the arrangement, S, to it. It is all brass, with the exception of a piece of ebonite, D, which can be moved backwards and forwards by the screw, B. On the piece of ebonite, D, there is a coil of wire, A, like an electro-magnet, but with a brass core which goes right through the ebenite, and is connected to screw B, and on top of which is a binding screw for the reception of a wire. The ends of this coil lead to terminals, CO, which have binding screws also for wires; this, I suppose, is a shunt of some sort, but I cannot see how it is to be used or the object of the scale marked on one side, as nothing comes in contact with it but the ebonite, D. On the edge of the ebonite are the figures 307 U, which I suppose is the resistance of the shunt, and 45 E, which I don't know the meaning of. The terminals, FF, are, I suppose, one for the resistance coils, and the other for the line to be tested. In American galvanometers of this class the inside ends of both coils are brought together where the battery connection is made by means of a key. The only place on this instrument for connecting the battery is, as far as I can see [34064.]-Geometry.-Can any of your readers in- (and I have taken the whole thing to pieces), the bindform me to whom we are indebted for the propositions ing screw, A, where it would make connection through usually found in elementary treatises of solid geometry, screw B and the sides of Fig. 8, with brass case of instrucomparing the surface and the volume of a sphere with ment, but still not with the coils of galvanometer; so I the surface and volume respectively of the circumscribing took off the cross connection and connected inner ends of cylinder? Have they come down to us in "Euclid's Ele-coils to the brass case of galvanometer. Please say was I ments," or are they of more recent origin ?-E. C. C. right in doing so, if the instrument was faulty in con[34065.]-Polishing Object-glasses.-What is struction, and the meaning and object of apparatus shown used in polishing object-glasses for a telescope ?-J. B. in 8. It was only after making the above alteration that ORRELL I could make any use of it, yet it does not work to my satisfaction, for in measuring a small coil of fine wire I had 50 units unplugged in resistance box. When the needle wanted 3 or 4 degrees of Zero, I unplugged 2 more units-no movement in needle; unplugged 5-a scarcely perceptible movement; unplugged 10, replacing plugs 5 and 2, when the needle flew right over, and although I replaced 10 it still refused to come back, and I [34066.]-Electro-Magnet.-I have a soft iron horseshoe, and wish to know what size and length of wire I should use in order to develop its greatest power with a battery of 10 half-pint Bunsens? Length of iron from poles to top of bend 9in., straight available space for wire 6in., diameter 13in., clear distance between poles 24in. X. Y. Z. had to replace 5 and 2 to bring it to its first position, so that 43 units kept it in the same position that 57 did before it swung. All the wire connections were carefully scraped bright and plugs of resistauce box brightened with emery paper, grit wiped off, and carefully screwed into their places in connecting the resistances.-JUAN CRUZ, Buenos Aires, 28th July, 1878. [34071.]-Brown Paint used in Carriage Painting.-I have a trap I wish to paint. I want to know how the brown is made with which carriages are generally painted (a kind of plum colour)? Have tried black and vermilion, also black and Indian red, also Venetian red, but none of them have that rich tint required.-YOUNG PAINTER. Boiling.-Could some reader favour me with a recipe [34072.J Amateur Confectionery - Sugar will not be sticky or run? I use tartar in boiling, but it to boil sugar, so that when I have kept it some days it will run.-O. S. simple electro-magnetic machine suitable for lighting a [34073.]-Electric Lighting.-I want to make a workshop 50ft. x 36ft. x 15ft. high. The machine must be simple in construction. Will some one kindly assist me, and send sketch and description? We have plenty of spare engine power.-TYNESIDE. Ovens.-On referring to a back number of the ENGLISH [34074.] Heat Regulator for Annealing simple form of apparatus for regulating the heat of gas, MECHANIC I find "R. P. G." (33416, p. 504) describes a which, he says, might be also used for regulating the heating power of a small furnace by controlling the supply of air. Although I can conceive its utility for regulating a supply of gas, I do not quite see how this apparatus could be applied to regulate the temperature of a furnace, which in my case would be about ift. square to heat an oven or kiln to about 270° F. The problem I require to solve is that of maintaining a uniform temperature in the oven, and if I can make it self-acting, so as to be independent of the stoker, so much the better. I fear spirits of wine would not do. Some plan, based upon the expan. sion of metal rods, with a suitable arrangement of levers to act upon the dampers would be preferable. Could any correspondent inform me if any such plan is actually in use for annealing ovens, and how the heat is usually regu. lated in them ?-ETNA. [84075.]-Solvent for Hair.-Can any reader inform me if there is any solvent for human hair; and, if so, what is its composition ?-DYER. [34076.]-Ventilating a Bedroom.-Will some obliging correspondent inform me if the following plan will answer ?-To knock an oblong hole in the chimney breast, near the ceiling, and cover it with perforated zine or iron which has previously had some cotton wool attached to it, to keep back soot? I am afraid to venture without getting to know whether the smoke is likely to come through into the room when the fire is burning, or is there a better plan ?-L. D. L34077.]-Gum Paste.-Will some competent reader kindly answer me the following questions ?-1. What quantity of gum dragon to 1lb. sugar; also what stiffness the paste should be? 2. What is best for dusting the moulds with? 3. Ought the paste to be taken out of the moulds when soft or hard ?—ÂN ANXIOUS ONE. [31078.]-Coke for Chilling.-Can any of our readers enlighten me as to which is the best kind of coke to use (in cupola) for chilling cast-iron-that is, the coke which will produce the deepest and most effectual chill on cast-plates? I have tried a variety of sorts, containing less and more sulphur, but cannot obtain satisfactory results. I use the best known chilling iron made in Eng. land.-STAEM. [34079.]-Slide Rule.-Will some one kindly give me a rule to find the distance between each figure on the slide rule, so that I can make one any radius I like ?-S. S. [34080.]-Stearine Candles.-Is the process of making stearine candles patented? Where can I obtain the wick or cotton for making snuffless dips ?-J. H. [34081.]-Le Chatelier Brake.-I hear that the Midland have one or two engines with the Chatelier brake. What is it, and how does it work P-PASSENGER. [34082.]-Engines at Paris.-At Paris last week I saw a fine engine belonging to the Eastern of France, 7ft. 6in. coupled. Can any one give details ?-PASSENGER. [34083.]-Co-ordinate Geometry.-Can any of your correspondents explain the meaning of the following question, taken from Todhunter's "Co-ordinate Geometry," p. 265 P-"If normals be drawn to an ellipse from a given point, the points where they cut the curve will lie on a rectangular hyperbola which passes through the given point, and has its asymptotes parallel to the axes of the ellipse."-G. J. B. [34084.]-Aniline Marking Ink.-Can any corre spondent tell me what I should mix with hydrochlorate of aniline to make a permanent marking ink in one liquid like that sold by chemists P-T. B. [34085.]-8mall Beam Engine.-I have a cylinder 24in. stroke. Will any correspondent give me the length the beam should be ? Also how the parallel motion is arranged to keep piston rod from bending, and any other hints? I will advertise address if any one can supply me with a working drawing.-T. B. [34086.]-Steel Manufacture.-Can any one give a description of Huntsman's process for the above, or name of a good book on the subject? I believe the uncemented bar is melted in contact with charcoal.-CARBON. [34087.]-Hardening Gravers.-How do Prescot toolmakers harden these? Sometimes I soften mine, and "file up," and making them red hot plunge in oil or water. They do not, however, keep a keen point, and are brittle.-LIVERPOOL FINISHER. [31088.]-Figures in Indian Ink.-Is it possible to obliterate figures of Indian ink tatooed on or pricked into the arm? If so, how ?-BUTTERFLY. [34089.]-Reading Single Needle Instrument. -How can I make a simple instrument by which I can learn to read and make the signs on the single needle telegraph instrument ?-TELEGRAPH. [34090.]-Crusaders.-Can any one confirm me in my belief that when the legs of a soldier are crossed at the ankle it betokens that he has been to the Crusade once, when crossed at the knee that he has been twice, and when crossed at the hip that he has been twice, and is ready to go again ?-F. C. HAWKS. [34091.1-8. E. R. Locomotives.-Could any of your readers give particulars of engines Nos. 34, 72, 81, and 847-W. A. F. [34092]-Bill of Bale.-Will some of "ours" kindly explain the routine throughout of a bill of sale ?-DINNY DUCKIE. [34093.]-Horse-power of Engines. Would "T. E. J." (33769) kindly give the rule for calculating the power of compound engines? I have seen the second formula he mentions used; the high and low pressure cylinders being taken separately, and the two results added together. It appears to me that in calculating the power developed by the high pressure engine an allowance equivalent to the average pressure in the low should be made for back pressure, while in the large cylinder the amount of vacuum in pounds should be added to the preseure of steam to obtain a correct result.-C. G. [34094.]-Miniature Coil.-To "SIGMA."-I am about to construct a small pocket coil for medical purposes, but before I begin I should like to be instructed in the following points (coil about 2in. long between ends, ends lin. diameter) :-1. Size and quantity of wire for primary and secondary ? 2. Size of wire for coil about 5-16in. diameter? 3. Best material for tube into which core fits? 4. How to fix the core firmly in end of coil, so that it will be exactly in the centre of the other end, and allow a brass tube to slide over it for regulating ? 5. Best method of insulating each layer of wire? 6. How to make a battery of the chloride of silver form? 7. Number of cells to work the above well? I want the coil as powerful as possible. 8. Would it be an advantage to use a switch (worked over brass studs connected by branch wires to the secondary) on so small a coil ? Any other hints on the construction and working of the above will be gratefully received by an-AMATEUR. [34095.]-Enlarging Photographs.-To "PHOTO BRISTOLIENSIS."-In No. 388, August 30th, 1872, of the E. M., you describe and illustrate your method for above. Please state the length of long-bodied camera and oblige -SUCCESSFUL AMATEUR. 134096.]-Marine Engineer.-I am desirous of going to sea as engineer. I am 20 years of age, and have a fair knowledge of engines, machinery, &c., having been five years at collieries. What is the best thing for me to do? I am ignorant as to the duties on board, different grades, pay, hours, and time to serve before becoming first, also what examinations will be necessary.-A. B. C. [34097.]-Gravitation.-A coil of rope with a weight attached is found to weigh 8 tons, hung about two yards over a pulley. Supposing the weight to be lowered into a pit (by the same rope) 180 fathoms deep, what would be the weight over the pulley in the second case? If any difference please give the rule for calculation.-AN IGNO RAMUS. [34109.]-Electric Explosion.-Can any of your [34111.1-Indian C.E. Service.-Will some reader [34112.]-Property in "Lost" Articles.-I found sent a query about a snoring horse-can any one tell me of other reader, inform an old contributor as to the method (34098.]-L.B. and 8.C. Engines.-Two Palace 84099.]-Bone Cracking Extraordinary.Whenever I move my arms upwards my bones crack in a most extraordinary manner. It is the same when I stoop with my legs. Can any one give the reason why ? Am a great athlete.-THE OLD GENTLEMAN. [34100.]-Mining.-Would any of your readers kindly Inform me what the words horses' heads or cowls means in mining language ?-COLLIER. [34101.]-Oxford or Cambridge Examinations and College of Preceptors.-Will any reader kindly give me information respecting the above, or tell me where I can obtain it? I have had some years' experience in teaching, but should like if possible to compete in the above. Is there a certain age beyond which persons cannot become candidates P-THE DAUGHTER OF A CONSTANT READER. [34102.]-Stone Breaking Machine.-Is there a machine that will break stones for a carriage drive, and what is about the cost? I have about 10 miles of private roads to keep in repair. Over some of them there is heavy timber traffic at times, and I find it very expensive having the stones broken by manual labour. I should like full particulars as to the cost of such a machine, and where one could be seen at work, and the power required to break per yard.-WANDERER. [34103.]-Brighton Engine at Paris.-I am very pleased to hear that a gold medal has been awarded to W. Stroudley, Esq., locomotive engineer of the L.B. and S.C. Railway, for the engine which he exhibits. Can any of your correspondents give the chief dimensions, and also the number of this engine, and oblige a-LocoMOTIVE ENGINEER? [34104.7-Government Rewards for Telegraph Inventions.-The names of the inventors rewarded for inventions by the Government Telegraph Department (with the amount they have received) do not appear in Mr. Preece's paper, read before the British Association, or in your valuable article on this question. Can any one inform me where I can obtain this information P-ELEC TRICIAN. [34105.]-Positive and Negavive Metals.-Is not zinc the positive metal and copper the negative metal in a battery? And is not the positive pole the end where the current leaves the battery, and the negative pole where it re-enters ? In "Chambers's Educational Course" it states exactly the reverse.-DR. SYNTAX. [34106.]-Bichromate Battery.-Please describe the chemical decomposition and the electrical action in a bichromate battery. Also why the zinc does not require amalgamating for this battery.-DR. SYNTAX. [34107.]-Writing on Brown Paper.-Could you suggest any method or preparation in use, so as to render the surface of coarse brown paper smooth, so that it may be easily written upon ?-SEEDSMAN. [34108.]-Batteries for Telephones.-To MR. W. J. LANCASTER, Will you please inform me how to SPHINX All communications for the "Sphinx" should be addressed to T. MITCHESON, B.A., City of London School Cheapside, E.C. Owing to the influx of mathematical correspondence a little time will be required for a satisfactory perusal and election for insertion, the space allotted for the "Sphinx" being necessarily restricted. +1 788.-Let S be a segment of a circle of radius unity, C 2 v its chord, and v its versed sine, and let = Z, then C 8 = Z (1+1) Z3 (3+)+ Z3 (5+) - &c. sin. z, when n is an odd number, by means of the ex789.-Obtain the expression for sin. n x in terms of ponential form. Why cannot this process be followed Does any such difficulty occur in the when n is even ? half sum of its projections. 2. When perpendicular to 757.-1. When the line is parallel to both planes it is either it is equal the sum of its projections, one of which than the sum of its projections by the projection of it on vanishes. 3. When parallel to only one plane it is less inclined to both planes through its extremities draw the plane to which it is inclined. 4. When the line (b) is planes parallel to the original ones. Let P and b be perpendiculars from the ends of the line on the planes thus formed, and a, B, the projections; then (I. 20), & +P) 1, but (I. 47), 8) P; therefore much more is a + 1. Hence in any case the length of the line is not greater than the sum of its projections. 758.-(Maggie.)-Because angles A F C, AD C, are right angles, .. a circle will go round A F D C, described on AC as diameter. Therefore angles D FC, DAC, being in the same segment, are equal. Similarly, a circle will go round OFA E, because angles O FA, O E A, are DFC= angle E F C-i.e., OF bisects angle DFE; equal; but angle D F C is equal to angle D A C;.. angle right angles; .. as before, angles O FE, OFA, are similarly, O E bisects angle DEF; .. O is the centre of the circle inscribed in 0.-A. B. C. 761.-Angle AC Q = 2 x angle ABP (Euc. 3-20); ... B = 2 x But circle A XYP = 4 x circle A Z BQ; .. sector A B PS= 2 x sector A CQR; and subtracting AABQ=2x AACQ; .. rem. AQPS = 2 x rem. A Q R. -W. MORSHEAD. 762.-Putting the divisor 101 in the form 1 + 10 weget by dividing 73 Po + 10 P, +102 pg + 103. = Po +10 Pi + 109 (P2- Po) +103 (Ps - P1)+10+ (P1-P2+P) Dividing by 10% we get Fo+10 Pi (P2+ 10 Ps) + (P + 10 Ps), &c. (a). Every number that divides the divisor and dividend The Largest Circulation of any Professional Journal in the Kingdom renders the BUILDING NEWS the best medium for all advertisers of Building Materials, Artistic requirements, and Contractors' Machinery, and for all those seeking situations as workmen. The number and excellence of its illustrations render it the unrivalled representative of the progress of modern art, and the most complete record of ancient examples. Among its contributors are the leading architects and art critics of the day, and no trouble or expense is spared to make it the most accurate and comprehensive guide to all information connected with the Arts of Construction and Design. Price Fourpence, of all booksellers and newsvendors. Post-free 44d. Office, 31, Tavistock-street, Covent-garden, W.C ANSWERS TO CORRESPONDENTS. All communications should be addressed to the EDITOR of the ENGLISH MECHANIC, 31, Tavistock-street, Covent Garden, W.C. HINTS TO CORRESPONDENTS. 1. Write on one side of the paper only, and put drawings for illustrations on separate pieces of paper. 2. Put titles to queries, and when answering queries put the numbers as well as the titles of the queries to which the replies refer. 3. No charge is made for inserting letters, queries, or replies. 4. Commercial letters, or queries, or replies are not inserted. 5. No question asking for educa tion or scientific information is answered through the post. 6. Letters sent to correspondents, under cover to the Editor, are not forwarded; and the names of correspondents are not given to inquirers. The following are the initials, &c., of letters to hand up to Tuesday evening, September 10, and unacknowledged elsewhere: TELESCOPE TELE.-Essex.-Hugh Clements.-B. McGuire. of the simplest, and is almost perfectly painless, being Now ready, in one vol., atlas folio, pp. 46 and 24 folding plates cloth, price 15s. mooted; but the Revue des Deux Mondes appears to THE STARS IN THEIR COURSES. have utilised your letter for its article.)-R. S. (The W. W., W. P. M., Chemicus, also reply to queries simi- NOTICE TO SUBSCRIBERS. Subscribers receiving their copies direct from the office are requested to observe that the last number of the term for whiop their subscription is paid will be forwarded to them in a PINE it is desired the Subscription. A two-fold series of Maps, with a Catalogue, showing how to identify at any time of the year all Stars down to the 56 mag., inclusive of Hels, which are clearly visible in English latitudes. By THOMAS SEBASTIAN BAZLEY, M.A., Author of "Notes on the Epicycloidal Cutting Frame," and an "Index to the Geometric Chuck." London: TRUBNER & CO., Ludgate-hill. Third Edition, greatly enlarged, crown 8vo., 4s. 6d. (postage 5d.) LOCOMOTIVE ENGINE DRIVING: A Practical Manual for Engineers in charge of Locomotive Engines. By MICHAEL REYNOLDS Comprising, besides other additional matter, "A KEY TO THE LOCOMOTIVE ENGINE.' "Supplies a want, and supplies it well."-Engineer. CROSBY LOCKWOOD & Co., 7, Stationers' Hall-court, E.C. This Day, crown 8vo., with Numerous Wood Engravings, price 71. cloth (postage 5d.), MECHANICAL DENTISTRY: A Wrapper, as an intimation that a fresh remittance is necessary. IMECHANICAL Practical Treatise on the Construction of the Various Kinds of Artificial Dentures, comprising also Useful Formule, CHARLES HUNTER, Mechanical Dentist. TO AMERICAN & BELGIAN SUBSCRIBERS. Tables, and Receipts for Gold Plate, Clasps, Solders, &c. By •.• American and Belgian Subscribers, especially when renew. Ing their subscriptions, are particularly requested to advise the Publisher of the transmission of the Post-office order, and the exact amount for which it is made payable. If the last-mentioned CROSBY LOCKWOOD & CO., 7, Stationers' Hall-ct., London, E.C. pating the la omitted, some dificulty is very likely to occur in ob- DRAWING & ROUGH SKETCHING amount. Subscribers in the United States and Belgium can be supplied with the ENGLISH MECHANIC post free from this Office, for the sum of 138. (3 dols. 250. gold, or 16fr. 800.) per annum, payable in advance. The remittance should be made by International Post-office order. Back numbers cannot be sent by the ordinary newspaper post, but must be remitted for at the rate of 4d. each to cover extrs postage. MARINE ENGINEERS. Price 38. With Explanations, Instructions, and Examples. Also How to Design Engines, Bollers, Propellers, Stop Valves, &c., and Examination Papers. for Assistant Engineers and Students in H.M. Navy. By JAMES DONALDSON, Engineer. London: CHAS. WILSON, 157 Leadenhall-street. Liverpool: PHILLIP, SON, & NEPHEW, South Castle-street. Glasgow: MCGREGOR & CO., Clyde-place. By R. H. WARN, Practical Tin-plate Worker. Containing practical and simple rules for striking the various patterns required for Sheet Iron, Zinc, Copper, and Tin-plate Workers. Illustrated by 32 Plates and Diagrams. This work has been examined, practically tested, and received 54, MARQUIS ROAD, CAMDEN SQUARE, LONDON, N.W. Indexes for each hair. yearly volume up to Vol. 2 (except Vols. THE SCIENTIFIC BASIS OF MUSIC. Subscribers are requested to order Cases and Vols. through By W. H. STONE, M.A., M. B. Oxon, F.R.C.P. Being No. 11 of Novello, Ewer, & Co's. Music Primers." Edited by Dr. STAINER. 8vo., paper covers, 1s., paper boards, le. ed. London: NOVELLO, EWER, & CO., 1, Berners-street, W.: and 80 and 81, Queen-street, E.C. else a large battery, which would be expensive.)-A. per Iine. No front page or paragraph advertisement inserted for HOW TO PURCHASE A PLOT OF LAND BRENTFORD. (In a reporter's vocabulary a "thunderbolt" means the electric flash.)-FRANCES LILY. (We should like to see so wonderful a fowl.)-B. (We fail to see the purport of your letter; if Swedenborg really demonstrated the truth of theories which were subsequently regarded as the great discoveries of others, there should be no difficulty in establishing his claims; there is, however, a vast difference between assertion and demonstration.)-F. C. HAWKS. (Try placing it near an ant-hill, protecting from wind and rain by a board or two.)-O. P. Q. (See the "Civil Service Guide," published by Cassell.)-POOR RELATIVE. (Much too complicated for any one but a solicitor, who would need time and payment.)-PHONO. (Rather a cool request; but apply. say, to the secretary of the Naturalists Field Club in your town.)-H. A. F. (Northcott's "Lathes and Turning" (Longmaus) and "The Lathe and its Uses" (Trübner). Mr. Hines, of Norwich, we believe, publishes a little book on the subject.)-ANXIOUS BROTHER. (The operation is one OUR EXCHANGE COLUMN. The charge for Exchange Notices is la. for the first 16 words, and 6d. for ENGLISH MECHANIC to present date, clean; part of Strong Iron Amateur LATHE, two beds, chucks; for ENGINEERING (volumes 15-20) for Sale, or exchange for popular science books.-G. W., 123, Islington, Liverpool. |