ENGLISH MECHANIC AND WORLD OF SCIENCE: No. 831. Having fixed on plan the dividing lines, it is a simple matter to stake off in field.-J. R. TAIT. [42930. Practical Land Surveying. Having laid the plan of the field correctly down on paper, take a fine silk thread, tied to the ends of a piece of whalebone to form a bow, which will keep it stretched. Then reduce the irregular side of your field into straight sides by means of this bow; lay the stretched thread on the irregular line, and look carefully you bring into the field as much outside ground as you cut off by thread, and draw a straight line. Your principal care is to see as much as you cut off you add to; then having the irregular lines resolved into straight ones, it is now easy to divide into triangles, &c., and compute quantity. If the above is not clear write again.-WORKING TOM. lings one sovereign; of the bronze 480 pennies [42944.]-Horse and Man-Power.-Nominally, [42941.]-Model Marine Engine and Boiler. -To "SUNLIGHT." -No trouble at all; simply a pleasure to help you I would not advise more than one siphon to oil-cistern; that might be, however, fin. or in. diameter, as the quantity of spirit a siphon wick of that size would pass is ample. The reservoir or cistern for the spirit is best made to fit the run of the boat, so that the weight of the spirit be kept low down. I should make it of sufficient capacity to hold, say, 1 pint of spirit. Less would do, just as well; but it would then need replenishing oftener. It might be, say, 6in. long and 4in. deep, and the width of boat, as it is well not to have it more than two-thirds full, as the rocking of the boat is likely to make the spirit wash about and so rush down the siphon tube too quickly.-SUNLIGHT. Bronze..Penny.... oz. Av., or 146 [42943.]-Weight of Coins.-I have given you below the weight of each coin from a sovereign to If you should require any further ina farthing. formation I shall be pleased to give it you. Sove 123 274gr.; half-sovereign, 61-367gr.; reign, crown, 436-36g.; half-crown, 218 18gr.; florin, 174-54gr.; shilling, 87-27gr.; sixpence, 43-63gr.; fourpence, 29-09gr.; threepence, 21-81gr. Then the bronze coins are: penny, 5 34drm.; halfpenny, 3.20drm.; farthing, 1.60. The latter are Avoirdupois weights, the former grains of Troy weight.-W. J. LANCASTER. (42950.]-Electric Light for DissolvingViews.-I wish to adapt the electric light to a triple lantern. Can any of your correspondents advise me what is the best lamp for the purpose, the space within the lantern being limited? Also, what battery I should require, or from what other source the power could be obtained, and what mechanism for dissolving? Is the electric light sufficiently steady for the purpose?-PHOTOGEN. [42951.]-Focus of Lens.-I have a photographic lens, and wish to learn its focus. Will someone who understands kindly explain clearly how I can find it? I wish to know what is meant by 6in. or 8in. focus.[42952.)-Bunsen Battery.-Thanks to Mr. LanPHOTOGEN. Will anyone kindly caster and others who kindly answered my last question with regard to the induction coil. tell me why a Bunsen battery which I made (the external cells being a wooden box divided into six partitions, all elements when each outer cell consists of a separate jar? most carefully insulated and thickly coated with shellac varnish) should give a very inferior current to the same I would also like to know if it is possible to have a recommended, and when the hammer is vibrating, worked Bunsen battery in this form. With regard to the coil with one small bottle bichromate, I get nearly in. spark; mentioned in question 42559, I have fitted up the coil as [42943.]-Weight of Coins.-A half-crown but when I hold the iron clapper in my hand and jerk it weighs new oz., a florin 2-5oz., a shilling 1-5oz., suddenly away from the platinum screw I get a much a sixpence 1-10oz., a fourpenny-piece 1-15oz., and longer and brighter spark. The spring of contact-breaker [42953.]-Tank Engines.-Can any reader give me a threepenny-bit 1-20oz. Penny, halfpenny, and is very strong. Can anyone suggest what is wrong, and dimensions and, if possible, a sketch of L. B. and S. C. Buryhill," No. 287, farthing weigh respectively, 1-5, and 1-10th of I shall feel grateful.-C. M. G. As the exact weight in grains may be 29-091 R. four-coupled tank-engines like " and " Withyham," 281, and of S. E. R. bogie tank useful, I append it in table form:123-2745 | Fourpenny "" give Sovereign 145-833 procure drawings or photos. of same?-MOTION LAMP. Half-sovereign 61 6372 Threepenny.... 21-818 engines like No. 149 and 84, 115, or tell me where I could 87.500 [42954.]-Water-Motor.-Can any of "ours Half-crown.. 218.182 a rough sketch of working parts of Bailey's water-motor advertised in this paper?-SATURN. Sixpence [42955.]-Force Pump.-Can anyone inform me of [42957.]-Lantern Condensers.-There is a paper [42958.]-Triplexicon.-Will any reader using the [42960.]-Geometric.-Can any of our valued sub- the eave to ridge. I want to work out (geometrically) [42961.]-Lathe Query.-I have an expensive and excellent lathe which, up to the present time, has given me much satisfaction: A few days ago I put on it a chuck which, I think, I have never before used. When done with, on endeavouring to remove this chuck, I was unable to do so, and the united efforts of two men were not sufficient to unscrew it from the mandril, so the lathe remained useless for several days. We at length removed the chuck by the application of a strong wrench; but as this is rather a violent remedy to apply to an almost scientific instrument, I wish to ask if any of your readers can instruct me how for the future to avoid such an accident.-G. W. [42962.]-To "Sperans."-Am I liable to pay income-tax, or any other imperial or local rates on a house which is unlet, but in which I have placed a caretaker who pays, of course, no rent? Does the fact of anyone living in the house make it liable to rates as above or to inhabited house duty? If not, how am I to proceed if the rates are demanded?-M. C. H. [42963.]-Steam-Pipes.-I wish to erect a range of steam pipes varying from 6in. to 2in. diameter, drawing off the steam at varying points for different purposes. These already known points I can provide for by having junctions cast on; but should it, as is likely, become requisite to take steam at other points, how can I attach my smaller pipes to this large main? For instance, to a 3in. or 4in. main, could I attach a 2in. wrought pipe by drilling, tapping, and screwing in the 2in. pipe. My man tells me he has seen it done, but that it usually was a bad job and leaked. I have seen it done by clips, but these were ugly to look at, and never tight. I feel sure there must be some reasonably practical mode of doing this, but my experience of this kind of work being very limited [42964.]-Sewerage.-I have seen it published in an I shall feel thankful for any assistance.-C. H. the best medium of sewage. Undoubtedly, if the joint is influential journal that cast-iron pipes under a house are made tight, as in gas and water mains, that is an advantage, but I apprehend that (1) the pipes would clog and eventually become choked; (2) that they would rust internally and externally, and consuine away. Ware pipes, being in short lengths, are liable to sink, causing stoppage (very noticeable on each side of foundation), but, being opinion on the subject.-WM. CARRICK. glazed, are not liable to corrosion. I shall be glad of any [42965]-Lathe Speeds-Overhead Motion.Given an outside flywheel 18in. diam., driving a pulley 9in., then from same shaft (pulley shaft) small pulley of of latter compared with one revolution of flywheel? 2in. driving one on mandril of 6in., what would be speed Also, the speed if the two latter pulleys were reversed.H. HENDLEY. [42966.]-Benzoline Gas.-I once made some good illuminating gas with hydrogen, made of diluted sulphuric acid and old nails, but if any air got mixed with would it condense if stored in a gasometer? This, I it an explosion would take place. How can this be prevented? What would be the cost per thousand feet, and think, is the better way to make benzoline gas of a good tion will be esteemed.-JIMBO. quality, if it can be made cheaply and without any fear of explosions. Living where there is no gas, any informa [42967.]-Drilling Apparatus.-Will "Sunlight" not revolve, and yet "Sunlight" says spindle I is lifted by spindle K? Will he kindly say what width the kindly answer the following ?-Having referred to reply 42805, Dril-ing Apparatus, how is spindle I attached to standard is where the bearings are? Also, how drill is spindle K when spindle I revolves and spindle K does fastened in spindle I, and how is wheel D fastened to sleeve H, and is sleeve H prevented from moving up and down by collars at bearing, or by the wheel D, and what prevents set pin from falling out of groove Z?-ED. [42968.]-Stylographic Pens.-Can any of "ours" or rather with pencils? I have used one for some months, give me any hints from experience with these new pens, and like if immensely; but there are certain drawbacks which perhaps others have found a remedy for. Firstly, their too funt writing, What ink can I use, not coloured, that wil write as black as ordinary ink with an ordinary on is if a movessary failing from construction? I have Me Writing done by a "style" which seemed a good deal backer than I can produce. I may mention that my pen was bought at Partridge and Cooper's, in Canceryine and has no name on it, only a number and Jate of patent. Secondly, when carried in pocket the Seating of air inside seems to drive the ink into, and even out af, the point, and when first used, the first few Tires are Nack and thick from too free flow of ink, after which the supply subsides into its normal faintness, thus prouerg an uneven patchy look. I had some idea of making a small hole in the air cap, but do not like to sp an expensive pen without a more competent Forn on the probable result. If these two defects could De raiticated, the pen would be just perfection, always ready, and no plaguey dipping ink to take up time and hek the flow of ideas. By the way, are the points really I m! I thought iridium was exceedingly hard, yet and mine would yield to a fine file and also to oilstone, As I smoothed a slight roughness off the point with the greatest ease.-TREADLE. -Bending Iron Pipe Coils -Will some readers give a little advice to a mechanic in the building trade, how the wrought-iron pipe coils are bent, such as fin. and lin. iron pipes, &c. !-Í. BOOKER. (42970)-Mirror (P).-I have a concave circular piece of I suppose speculum metal, 54in. by jin., fixed into a carefully-worked ornamental circular box made of mahogany, inlaid, and with movable lid, having a brass ring by which to suspend it. I know nothing of its history, but it is, doutless, of some antiquity. It magnifies the face, not brightly, but very considerably. Is it an ancient mirrer, in use before glass mirrors were made!JOSEPH T. FISHER. 42971-Bookbinding.—I have bound two volumes of ENGLISH MECHANIC, also several others, but fail in making labels for the backs. Will someone kindly say bow it is done! I have a set of steel letter stamps such as are used for stamping metal, gold-leaf, gold size, &c., but cannot manipulate to my satisfaction.-KIKO. 142972-Mangle Shafts.-Will some of "ours kindly inform me the best means of forcing mangle shafts into wood rollers of wringing and mangling machines. Sketch would greatly oblige, if Editor could spare space. It would be a great boon to many mechanics, as some one has frequently to repair these machines in every town.-MANGLE. 42973-Intensifying Negatives.-Would some one kindly help me out of the following difficulty!-I can take positives on glass well, but when I try to take a negative I find it impossible to intensify it. I use Mawson's negative collodion, and make up all solutions according to directions on the bottle. The plate behaves well under the developer; but when I try to intensify, the intensifying solution becomes turbid at the first or second application. I have read in books that just before the red fog" commences there is a peculiar change observed in the high lights. Can anyone make that phrase clearer to me! I use a portrait lens, -plate, by Stanley B quality. Should I intensify in the dark room! I was told that it should be performed in the open daylight. "Sunlight" promised to help a reader to get a negative for a copy. If he would help me I should be most happy to advertise my address.-J. W., junr. 42974-Drilling Apparatus.-Will "Sunlight," with his usual kindness, say, in regard to his drilling apparatus on page 550, if the round strap will have grip esazh to drill up to jin. holes? Is a high speed (within certain limits, the best for general blacksmith's work, as all the bench drilling machines I have seen had no acseleration of speed on the drill spindle. As I am thinking of making one, any hints from him will be gratefully reeived. How does he connect spindle I with K-J. 42975)-Model Loco-Will "Sunlight," or other barber, kadly advise me if any modern express paswen lab, onld be modelled to, say, or ¡in, scale, to ▼r atafetonly, and with spirit-lamp in firebox! I tongit & ample style was the L. and N. W. with single frame and sumpled drivers as L. C. and D. Will someone my viere I did and cale drawings of these? There are done in lack numbers of E. M. to 1870. Or would a Woah wage engine be a better style, as giving more your ad fumace power to same size cylinders Trout male rodels of modern locos, with reduced quadam va vou, or be too weak? I observe model site have cosači touders in proportion to size of cylinders und mitig What exact diameter have I to turn them! 393, with cylinder 3in. bore, 6in. stroke, but should like [42981.]-Beer-Pipe Joints.-Will a brother-reader learner, so probably the following supposition is all land cement? And being in the country, where I cannot [42993.]-Feed-water Economy.-Would any of your readers tell me what saving I should effect sup posing I increase my feed-water from 90deg. up to 240deg. by means of an economiser. An example worked out in its simplest form would greatly oblige a-Fun 142994.]-Lantern Gas-Bags.-The cost is wedge-shaped gas-bags is so high. How would a ciren. lar one, 15in. diameter, and 18in. high, do! The indiarubber cloth fastened to circular end boards bottom arů top, with 14in. projections to take iron rods on which feet, and the top carry a board for lantern, the whole the bag would slide. The lower ends of rods would form would, I think, be portable, and come cheap. Pleas forming oxygen-holder and stand for lantern; and advise an-IRISHMAN. [42995.J-Cesspool -I have lately purchased a house in the country. Before purchasing it, I was told that there was a cesspool belonging to the house on the ground; this I did not mind, as I decided to disentinue its use and use Moule's earth closets; but, an taking possession, I was told by the vendor that my neighbour's cesspool was also in my ground. Can any of "ours" tell me under whose control the latter cess pool is? Who should clear it? Has my neighbour any right to come into my ground at any time, convenient ar inconvenient to me, to clear it? Can I close it without Ehaving to make him a new one in his own grounds.-G. HARRISON. for simplicity, that there are only two colours composing [42996.1-Silk.-Wanted a solution that will give body, gloss or glaze, and still retain the softness of the articles, which, by the bye, are coloured.-NEXO, [42997.]-Organ Accordion' (Busson's). - How can I repair a broken key?-NEMO. [42998.]-Organ-Would Mr. Dresser or other kind correspondent give end-section of bracket for 8. organ-front, not too elaborate, to project into room about 12in. over performer's head, and oblige! CREED. [42999.]-London University 1st B. Sc. Pass acquires a velocity of 40 miles an hour in 3 minutes on a Examination.--A train of 203 tons starting from rest horizontal railroad. Express, in statistical measure, the excess of the moving above the retarding forces, each being assumed uniform, and assuming = 22-J CHERRY. kindly give me some idea of the proper way to set about oblige me by explaining why, in his interesting article en [43001.]-Determination of Heating-PowerTo Mr. ALFRED ALLEN AND "SIGMA."-In Mr. Fletcher's list of gas cooking apparatus," R. Briggs, Esq.," is quoted as authority for an experiment showing that a cooking 1in. iron pipe with jet-holes lin. apart, gave 244 units stove fitted with the Bunsen burner formed by a ring of heat for each cubic foot of gas, while Fletcher's pa solid-flamed burner gave 450 units for each cubic foot. The statement is so extraordinary that I should be glad to test its accuracy. Will these gentlemen, therefore, give me their ideas of what would be a fair way of conducting the test. In return, I shall be happy to publish results verified by some competent person. I have not, so far. been able to obtain particulars of Mr. Brigg's operandi.-H. B. [43002.] Ventilating Bath-room - Can any reader advise me how to ventilate a small bath room. The steam, when preparing a hot bath, completely tills the room, and leaves the walls dripping-wet. Would a large tin funnel put through ceiling, and projecting into loft above, draw off the steam?-WET. [43003.]-Phonograph.-I wish to make a phonegraph of the best form, except that I should profe handle to turn it or a weight, instead of clockwork. Will your correspondent, Mr. Lancaster, or any other, kindly either give me a sketch, or refer me to any back num bers in which a sketch or directions exist -B.M., FE C.S. [42988.)-Aerial Navigation.-I feel very much indebted to Mr. Thomas Moy for his reply to my letter (42812) on the above subject. May I trespass so much on his good-nature to put a few questions arising out of it? Given a machine with 32 sq. yards of aeroplane and a total weight with rider of 230lb., (1) what would be a "suitable forward motion" which would retard its fall and allow of a "slight upward inclination "occasionally! (2) How can I calculate surface friction and suitable forward motion? (3) What power would be necessary to produce that motion? As to superposed planes, would they not be much more effective in air than in water, the latter medium being less divisible than the former? I am anxious to use 12 planes 12in. apart, and would be Wheels-I want to make iron wheels about could one plane of 32 sq yards be made practically rigid 200 yards apart exactly in the meridian line. I can place glad to know proportional loss of sustaining power. How [43004.]-Meridian Line.-I wish to fix two posta in tamer, wh7, 8, 9, and 19 teeth to an inch, As to screws, would not two placed at opposite sides of, them pretty nearly so by means of a compass which I have, returning wheels other too small or too large; and some distance away from, the arrangement of aëro • zonde se vor get theexy dameter. Could anyone oblige planes be effective? Mr. Moy says: "Economy, light- with sights, allowing for variation; I want to adjust th ness, and efficiency are attained if the downward motion marks with a plumb-line and the Pole-star on some mor more accurately, and I think I can do so by ranging the the by sharing the exact diameter I have to torn them!of the ends of the planes is used to propel the apparatus." light night. Will" F.R.A.S." kindly say how I can find our LE 2777)-Polishing Elm and Oak Coffins-Wili he explain how the ends act, and if it would be pos- when the Pole-star is in the meridian of this place in any ster Kadly age me instructions to prepare sible to actuate them by pedomotive power applied to a County Limerick, lat. 52° 38' N.,long. 8° 22′ W., either above but you in visa sot ex fyffice, also to make polish that cranked axle, as in a bicycle? In the case of long narrow planes, should they be placed with their long edges much different from that at Greenwich? Does the Na or below the Pole! Also, is the magnetic variation be Frey quarkly with a quod glow?-Box. parallel or transversely to the line of flight.-RosiICRU cal Almanac inform on these points-AGRICULTES, one-Modelling Clay--Sculptors use a clay CIAN. What & the name of the clay, and the 142989.]-Predatory Animals and Rabbits.- [43005.]-Coal-Mining. How would you apply Salah Alam, and what process do they undergo Can any reader kindly inform me which animal, of a head of water of 50 fathoms (from pump set in shaft, Déus mixing? K. T. rabbit's numerous foes, is in the habit of turning its vic-work an hydraulic ram for forcing water out of workin 4279-Testing Sulphuretted Hydrogen-tim's skin inside out after finishing its meal! I believe mile away from shaft!-YouNG MINER. it to be a cat, but am not sure.-GARRISON GUNNER. [43006.]-Trinity High-Water Mark-Jam [42990).]-Induction Coil.-TO ME. LANCASTER. the maelstrom of an argument as to what constate What length of spark should I get out of a coil 6in. Trinity high-water mark. The definition that I have between the ends, fin. core, two layers of primary No. given is not considered good enough. The most curio 18, and 6oz. of secondary No. 38, both are silk-covered! thing is that reference to the usual sources and " By answering the above, you will much oblige-R. WIL- clos," where such a definition might be safely counted LIAMSON, Glasgow. upon as to be found, say nothing at all about it. Th speak of it in problems and instructions in almost every places me in very-Low WATER. page; but deuce a word as to what constitutes it. That W Torum Atmos:”- In the Mechanic of April 9th Wapata pih sungh to mention posable sources of vichy-Engine - To “Newttone."--I have commachs making an engine like the one described on page [42991.]-Crucible.-I would like to undertake a clay, and to be able to subject them to a heat as high few experiments by burning together burnt lime and as that used in burning Portland cement. Could any of your readers kindly inform me how much heat, what degree of heat, or what heat it takes to burn Port [43007.)-Angle of Lathe-Mandril-Can “Sun” light" or "Treadle" inform me what is the prop taper for the bearings of mandrils such as are fitted its centre a copper plug or piston which presses found elsewhere. It contrasts with a heavy five-mover as a sonnet does with an epic. Hence the charm which collectius such as this will always have, so long as the same ideas are not repeated too often.-J. PIERCE. THE CITY OF LONDON CHESS CLUB. The Annual General Meeting of the above, held at Mouflet's Hotel, Newgate-street, on the 18th, was attended by about 50 of the 121 members now enrolled, and was of unusual importance. Mr. Adamson was elected secretary, and Mr Lovelock president. A silver cup, value £16 16s. has been presented to the Club in honour of Mr. Murton (the oldest member) by Messrs. Manning, Cubison, and Jones. The balance-sheet shows a surplus of £2 98., in spite of heavy expenses, and the meeting passed off most satisfactorily. ANSWERS TO CORRESPONDENTS. All communications should be addressed to the EDITOR of the ENGLISH MECHANIO, 81, Tavistock-street, Covent Garden, W.O. 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. Letters or queries asking for addresses of manufacturers or correspondents, or where tools or other articles can be purchased, or replies giving such information, cannot be inserted except as advertisements. 5. No question asking for educational 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. • Attention is especially drawn to hint No. 4. The space devoted to letters, queries, and replies is meant for the general good, and it is not fair to occupy it with questions such as are indicated above, which are only of individual interest, and which, if not advertisements in themselves, lead to replies which are. The "Sixpenny Sale Column" offers a cheap means of obtaining such information, and we trust our readers will avail themselves of it. The following are the initials, &c., of letters to hand up to Wednesday evening, Feb. 23, and, unacknowledged elsewhere: F. YORK.-J. Wolstenholme.-David Brown.-T. Taylor. -C. Rabache.-F. G. Rose.-J. B. Spicer.-W. T. Underwood.-E. Bell.-R. Hardie.-Cyclops.-Soldering Iron.-H. W. B.-G. C. M. Hall.-N P. S.-W. L. Titley.-F. T.-Tin Smith.-Country Smith.-B. B. -A Miner.-E. Pennock.-York.-C. C. C.-Young Engineer.-E. Naish.-J. E. F.-V. B.-Technicus.Anglo Saxon.-One who Never Knew.-R. C. Biswas. -J. R. G., Sheffield.-Argent.-Sammy.-D. Young.M. W. Stevens.-Windy Nook.-H. W. W.-Brento.The Optical Bricklayer.-Seveerg.-Seconds' Practical Watchmaker.-8. Calton.-Col. Ross.-Copper and Zinc.-Fiddler.-B. Wood.-H. W. R.-Guido.-H. Winckelman.-Rosicrucian.-R. W. J.-J. Dresser.W. H. S.-W. J. M.-G. J. Burns. A NEW VOLUME. THE next number is the last of Volume XXXII. Readers willing to oblige us by recommending "ours" to new subscribers should do so now, when a new volume is about to commence. The index to Vol. XXXII. will be published in the number dated March 25, and cases and bound volumes will be on sale shortly after. Readers desirous of making up their sets for binding the present volumes are recommended to do so at once, as the back numbers soon run out of print. DIDYMOGRAPSUS. (Shall be glad to insert anything you may send on geology that may help our readers. With regard to microscopy, there is, doubtless, among our readers, as at the Microscopical Society, a "slug and bug," as well as a "brass and glass party. if the latter is, as you seem to think, too predominant in our pages, all we can say is, its adherents are more industrious as correspondents than their brethren.-G. MASON. (We have no further space to "explanations.' spare for mere We think that Tubal Kain's" letter may very well finish the discustion.)-H. BOOKER. (First query inserted. 2. Have you not read the article on the Glycerine Barometer on p. 532)-Z. Y. X. (See p. 624, Vol. XXIV., No. 624. Your practice is right as described; but surely you do not mean that you get the straw colour and they are still soft.)-J. R. (You must increase the draught by some means, or try a blast. No one can give useful advice without having a sketch at least of the arrangement before him.)-TANNEBERG. (The simplest method is to take a sheet of tinfoil and spread mercury over it, then slide the glass steadily on; but probably one of the processes described in Vol. XXX., pp. 415-6, will be best for an amateur If only for a looking-glass, it is cheaper to buy the glass ready silvered.)-IDE HAYES. (File the cast-iron clean, wet the surface with muriatic acid, and apply the tin and the soldering bit.)-J. A. L. (See p. 545, Vol. XXX. The composition is glue and glycerine, with whiting, barytes, or plaster of Paris added, and scented with carbolic acid, oil of cloves, or anything else. The ink is made by dissolving aniline in alcohol, and diluting with water. The question has been answered hundreds of times in the last three volumes.)-Y. (The old shot-towers by Waterloobridge are still in existence, and apparently working The metal is shaken through a sieve and falls into water at the bottom of the tower.)-F. H. M. (See p. 69, Vol. XXXI., and recent indices. If the message is printed," the paper requires no preparation.)MONITOR. (The best plaster of Paris and water. Use glue-water to retard the setting. When set, dip in melted stearine, and it will resist water for many years.)-GLATTON. (We have no recollection of either of the subjects you refer to. Several devices for obtaining the first in black volumes, but we know nothing of the article on Sand.)-J. W., Jun. If you buy the polish at any respectable shop, you may know that it is Bun (See W. E. W.-J. A.-Wm. Hawes.-Mechanic.-J. R. T.Working Tom.-Working Lad.-Treadle.-T. Forty.W. H. W. P., and others have replied to queries already similarly or adequately answered. 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. 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Reduced terms for series of more than 6 ADVERTISEMENTS in EXCHANGE COLUMN-for Twenty-four words . d 0 3 For every succeeding Eight words.. :: 03 ADVERTISEMENTS in the SIXPENNY SALE COLUMN. Sixteen Words .. For every succeeding Eight Words a. d. 0 It must be borne in mind that no Displayed advertisements must be prepaid; no reduction is made on repeated insertions: can appear in the Sixpenny Sale Column." All advertisements and in cases where the amount sent exceeds One Shilling the publisher would be grateful if a P.0.0. could be sent, and not stamps. Stamps, however (preferably halfpenny stamps), may be sent where it is inconvenient to obtain P.O.O.'s. for. The address is included as part of the advertisement and charged Advertisements must reach the office by 3 p.m on Wednesday to insure insertion in the following Friday's number Epps's Cocoa.-Grateful and Comforting.By a thorough knowledge of the natural laws which govern the operations of digestion and nutrition, and by a careful application of the fine properties of well-selected Cocoa, Mr. Epps has provided our breakfast tables with a delicately-flavoured beverage which may save us many doctors' bills. It is by the judicious use of such articles of diet that a constitution may be gradually built up until strong enough to resist every tendency to disease. Hun dreds of subtle maladies are floating around us ready to attack wherever there is a weak point. We may escape many a fatal shaft by keeping ourselves well fortified with pure blood and a properly nourished frame."-Civil Service Gazette.-Sold only in Packets labelled-" JAMES Errs and Co., Homeopathic Chemists, London."-Also makers of Epps's Chocolate Essence for afternoons. NOTICE TO SUBSCRIBERS. the fault of the workman, if failure is the result. See pp. 175, 227. 2. Mix lamp or vegetable black with turps, and just sufficient gold size to bind it.)-E. S. (A simple duster ought to be sufficient, wetted with paraffin oil, say; but we suppose the gilt is worn off.) -W. J. J. (Lamp-black ground up in gum-water is the simplest inixture. You can buy the lampblack ready ground in tubes.)-AJAX. (The catalogue of the books in the reading library can be had for 3s. 6d., but the catalogue of all the books is in MS., and can be seen only at the reading-room. Of course, all the books you mention are there.)-T. (You can grind up real gold-leaf with honey, or buy the gold-coloured powders, and apply with gold size. 2. Simply rubber dissolved in bisulphide of carbon.)-W. E. K. (The top hole is usually nearly closed. Why not get a tutor containing fingering)-STEEL. (Dr. Percy's "Iron and Steel," Murray, is the best work. The second part of the question cannot be answered without knowing what experiments you wish to carry out.)-CYMRO. (See the index of the last volume, under head Observatory," "Observing Tent." You will find something to suit.) MIZAR. (In Webb's "Celestial Objects," Longmans, or an elaborate one of Mr. Birt, Leyspring-terrace, Cowley-road, Leytonstone, Essex.)-BAL-NA-CILLE. (The best black for the purpose is chloride of platinum dissolved in water, and applied with a soft brush. The "black" is then in the surface of the metal. There is no secret about it.. Any optician will do it for you.)A NEW BUB., Chelsea. (See a reply on p. 501, and for black dye see p. 273, Vol. XXXI., or consult the indices.) -MUSICA. (See p. 277, Vol. XIX., and p. 384, Vol. XXIII. The other question was answered on p. 475 (reply 42468). See also the indices of the last ten volumes.)-WORKING TOM. (Only a limited number of readers would contribute to such a club, and the designs would have to be printed by photo-lithography, which would necessitate separate supplements, and these we cannot afford. Those readers who are interested have their opportunity in connection with the Building News.)-A. (We know nothing about it. If we announced it, we stated at the time where further particulars could be had. We think it was the German Union of Railways.)-GILSTED. (The water is supercharged, and on being agitated gives up a portion of the gas held in solution.)-A. ROBERTS. (Dress them with arsenical soap, and "work them well to soften. See indices of back volumes.)-IGNORANT. (Boosey's, or one published by Metzler.) -ARTHUR. (See many replies in back numbers. No. 16 silk-covered, and the layers should be equal in diameter to the core. sen, Smee, or Daniell.)-J. C. B. (Good beach and good sea-fishing, but not trout.)-DULCIANA. (Brabner, 150, Kingsland-road, E.)-YOUNG FITTER. (You cannot do better than consult an oculist in your city.)C. P. (Too problematical.)-NoN NOBIS SOLUM. indices of back volumes. Given hundreds of times.)W. H. C. (Plaster of Paris, Stourbridge clay, or one of the compounds used for artificial stones.)-HEATHER TOP. (both would be affected by damp, but precautions could be taken.)-DOMESTIC ENQUIRER. (They are simply soaked for 12 or more hours before boiling.)MAPS. (Longmans are the publishers. They are superior, of course. We cannot give the formula, as we have not the book; but it is certainly not better than many we have given.)-ExQUIRER. (1. Pull them out. 2. Soap and water. 3. Longfellow. 4. By taking exercise calculated to lengthen the limbs.) AVIDITY. (Yes, to your first question; but see indices to back volumes.)-ALPHA. (Dissolve aniline in alcohol and dilute with water.)-W. AINSWORTH. (If you will obtain a guide to patentees from one of the patent agents who advertise in our columns, you will find replies to your nine questions.)-IMPROVER (Wood's "Guide," of Inman, New Wortley, Leeds)-CRUX. (From two guineas upwards. Certainly, with perseverance and an "ear for music.)-ATHOS. (Use coquilla nuts, vegetable ivory. Try the timber yards, or an advertisement in the Sale Column.)-EMIGRANT. (Apply to Messrs. Churchill, New Burlington-street, W., or Lockwood and Co., Stationers' Hall-court, E.C.) ENOD. (Adulterated with lighter oils.)-L. (To get sufficient head to force it through mains.)-R. C. B. (The range of distance is simply a matter of focus. See the tables of curves recently given.) -CONSTANT READER, Cork. (Geikie's "E.ements of Physical Geography" and Huxley's "Physiography," both published by Macmillan. If your object is merely to pass the examination, you should find out what books the examiners affect.)-CAROLUs. (Try it for pitch with a pianoforte, but it is scarcely wo.th expending money on. If, as we understand, it has only one key, it is simply useless as an orchestral or concert instruinent.) -M. A. C. (Elastic bandages are generally recommended; but take the advice of a medical man, which is generally cheapest in the long run. 2. We have frequently given recipes for tempering mill-bills, and can only refer to previous indices. See answer to "StoneDresser," p. 553. Sharpen by grinding, and harden in the ordinary way. You will find plenty of fancy dipping solutions in back numbers, but we suspect water with the chill off will answer as well as any.)-J. G. (Is it "salt oil" you have written, and if so, is there any other name? It is useless to expect a reply to so Vague a query.)-A CONSTANT READER. (The living brother is entitled to half the money, and the children of the deceased brother to the other half.)-STONE DRESSER. (One of the numbers we mentioned as containing recipes for preparations for mill-bills, that for The charge for Exchange Notices is 8d. for the first 24 words, June 5, 1874, can be had, post free, for five halfpenny stamps. Our notice means that the bound volumes are out of print. Most of our back numbers are to be had separately, and surely we may reasonably expect more recent readers to buy a back number at a cost of a few pence rather than fill valuable space with information already many times given.)-OLD SUBSCRIBER. (Turn them out of doors, and if they annoy you call in the police, or apply to the nearest magistrate.)-J. C. RIDOUT. (There is no charge for letters. Some of your objections had been anticipated by another correspondent, and we had already devoted all the space we could spare to the particular machine in question.)-VANDERDECKEN. (In type.) A. Z.-See indices to back vols. G. L.-Adham.-P. 8. A.-H. T.-Your queries can only appear in the "Sixpenny Sale Column." Subscribers receiving their copies direct from the office are requested to observe that the last number of the term for which their subscription is paid will be forwarded to them in a FixK Wrapper, as an intimation that a fresh remittance is necessary, if It is desired to continue the Subscription. TERMS OF SUBSCRIPTION. PAYABLE IN ADVANCE. 6. 6d. for Six Months and 11s. for Twelve Months. Post-free to any part of the United Kingdom. For the United States, 13s., or 3 dols. 25c. gold; to France or Belgium 138., or 16f. 50c.; to India (via Brindisi), 15s. 2d.; to New Zealand, the Cape, the West Indies, Canada, Nova Scotia, Natal, or any of the Australian Colonies. 138. The remittance should be made by International Post-office order. Back numbers cannot be sent by the ordinary newspaper post, but must be remitted forat the rate of 3d. each to cover extra postage. delphia, are authorised to receive subscriptions for the United Messrs. JAMES W. QUEEN and Co., of 924, Chestnut-street, PhilaStates for the ENGLISH MECHANIC, at the rate of 3 dols. 25c. gold, or Thirteen Shillings per annum, post-free. The copies will be forwarded direct by mail from the publishing office in issued after the receipt of the subscription. If back numbers are London. All subscriptions will commence with the number first required to complete volumes they must be paid for at the rate of 4d. each copy, to cover extra postage. Mr. R. M. TUTTLE, of 13 and 15, Laight-street, New York City, is also authorised to receive American Subscriptions at the rate of 3 dols. 25c. per annum. Vole. XXIV., XXVI., XXVII., XXVIII., XXIX., XXX., and Vol. XXXI., bound in cloth, 78. each. All the other volumes are out of print. Subscribers would do well to order volumes as soon as possible after the conclusion of each half-yearly volume in March and September, as only a limited number are bound up, and these soon run out of print. Indexes for each half-yearly volume up to Vol. X. (except Vols. II., III, IV, V., and X.) inclusive, 2d. each. Post free 24d. each. Cases for binding, is. 6d. each. **Subscribers are requested to order Cases and Vols. through their booksellers, and not to send direct. The regulations of the Post-office prevent their transmission through the Post. Holloway's Pills have many competitors, though no equals, for supplying the young and delicate with a simple strengthening and purifying aperient. These pills, composed of culiar to females, and are most serviceable at the critical periods the finest balsams, are particularly adapted for all complaints peof early and mature years. OUR EXCHANGE COLUMN. and 3d. for every succeeding 8 words. Exchange central-fire Breechloader for 50in. Bicycle, Coventry Club or other good make; or Turning Lathe,KOET. BROWN, Tunbridge Wells. Organ Windchest and Bellows, new and second-hand (ready for pipes); a 4-stop Organ, complete (except pipes). What offers-W. JOHNSON, 12, Moxley, Wednesbury. Students of Mineralogy can obtain specimen crystals of Ruby, Sapphire, Diamond, &c., at extremely moderate exchange.-F. POWELL, Lapidary, Salterton-place, Egham, Surrey. Remington Type Writer, revolving Stereoscope, with 48 glass stereos, Microscopes, Chromoscope, Magnetic En gine, and other Scientific Apparatus for exchange. List, I stamp. -JABEZ FRANCIS, Rochford, Essex. MARCH 4, 1881. ENGLISH MECHANIC AND WORLD OF SCIENCE: No. 832. The English Mechanic AND WORLD OF SCIENCE AND ART. is granted; whether a patentee should not beneficial to the nation at large by encoura- FRIDAY, MARCH 4, 1881. ARTICLES. I being made to settle the vexed question self or by his licensees, because the patent the duration of the latter to five years in The United States system is supposed by some to be the most perfect of all patent Laws; but Mr. Paine, the Commissioner, points out several serious defects, notably the rules referring to the duration of the For instance, foreign American patent, when foreign patents have thing. As to the compulsory clause, it seems letters patent granted to an American inalso been obtained. only reasonable that a patentee should be ventor the day before the patent was obthe near prospect of some endeavour compelled to work his invention either him-tained in his native country might reduce The of the Patent Laws, a number of opinions has been granted on the ground that the in- stead of seventeen-to whatever the durahave been recently expressed, and taken vention is of benefit to the nation, and if it tion of the foreign patent might be, in fact; Practically the solution of the day after the American patent, the in conjunction with the report of the Com- remains unworked the nation clearly gains whereas, if the foreign letters were granted missioner of Patents for the United States, nothing by it. lately issued, there is abundant matter for this difficulty solves the other, and it is latter would not be affected at all. the consideration of the Lord Chancellor or necessary only to fix a limit during which examining system, too, does not work enthe Attorney-General who is intrusted with an unworked patent shall have a claim on a tirely satisfactorily. For instance, an apthe duty of bringing in the Bill. That some subsequent patent which may be workable plicant, whose claim is allowed, but who reform of our Patent Laws is necessary, is and successful, for crude ideas are often neglects to proceed for two years, forfeits 'general analytic tacitly conceded on all sides: the differences patented which a subsequent inventor may absolutely his right to a patent; but if his was pointed out of opinion occur in connection with the utilise and bring to a successful issue. These claim is rejected, delay in proceeding with Com- matters are, however, of individual interest, an amended application will not forfeit his shape those changes should take. mencing with the fundamental principle of and in a matter of this kind the State can- right. The want of a a patent law, the object is clearly to en- not study the interest of individuals, but and descriptive index courage invention; and the problem is, how must be guided by the broad interests of the more than 30 years ago, and the present which are large. However serviceable to applicants, to do that to the fullest extent without nation. Every one knows that hundreds, commissioner urges its necessity on behalf interfering with the freedom of trade. It is nay, thousands of patents are taken out of the office, of inventors, and the public at notorious that of the 5,000, and more, every year for "inventions" patents annually applied for in this king- either useless or of so little practical value the appointment of examiners has proved, dom, only about 10 per cent. are of any that they are not likely to be utilised; and said the commissioner in 1848, the system real value, and die a natural death without every one knows, too, that even a really of search is necessarily defective; patents either benefitting or injuring any one useful invention takes three, four, or more have been issued for devices already figured These cations have been refused from the inability beyond lightening the pockets of the years before it can be introduced to any ex- and described in popular journals, and there Should Congress order patentee, and swelling the surplus income tent, especially if it is one involving the use is, be it added, just a suspicion that appliof the Patent Office. But looking to the of new plant in a manufacture. undoubted success of the patent laws of the years of waiting necessarily mean the ex- of the examiners to comprehend the merits United States, it is felt that the real in- penditure of considerable sums of money, of the invention. ventive talent of this country is curbed by and it is curious therefore to observe that the preparation and periodical publication the high fees charged by our office, which this fact has been made an argument for of such an index as Mr. Commissioner compared with the over, but with its publication the only argupractically prevent a working man from ob- not cheapening patents, ou the ground that Paine suggests, the work will be of the "drop in the ocean taining a patent unless he allies himse the patent-fees are after all but a mere greatest value to inventors all the world subsequent outlay required to make the ment in favour of examiners will vanish, for Another argu- agents, law-officers, and inventors will with a capitalist; and the main point es dispute is the necessity of reducing the fe payable at the first stage to a sum so invention remunerative. moderate that a patent will be within ment based on the facts above mentioned then be in a position to readily discover for of the reach any fairly prosperous is still more curious, for it goes on these themselves whether there is anything novel artisan. Looking at the question in the lines: that as a large number of patents are or not in an invention. It is worthy of abstract, it might be asked why the country utterly useless, would-be patentees should note that the number of patents issued by Seeing that a plus income has steadily increased. should demand any fees at all, seeing that a be deterred from protecting their "inven- the United States Office has steadily declined successful invention must be of public tions" by high fees, in order that their during the last four years, while the surcheck on benefit; but experience teaches that it is pockets may be saved. the patentee never finds out the real commercial home of invention in the States is clearly necessary to have some -one would think every 403 inhabitants; in Connecticut, 1 exuberant vanity of would-be patentees as value of his patent until he can put it on the indicated by the following figures: - In distinguished from inventors. Accordingly market-and he cannot do that safely until Massachusetts, 1 patent was granted for it has been suggested that the preliminary he has obtained protection,fees should be sufficient to a little more than that the proper way to save his pocket would for every 945; Rhode Island, 1 for every pay the expenses of the office, and that a be to lighten the preliminary expenses as 1,138; New Jersey, 1 for every 1,544; and tax should be imposed on patents which much as possible; and further, in the case New York, 1 for every 1,717. The figures continue beyond the first stage for every of a patentee who needs all his money to for Massachusetts are certainly remarkable, drop in the Americans, or what proportion are immiyear up to the termination of the period for push his invention for three or four years, and it would be interesting to learn what which the letters are granted. The public the £50 stamp at the end of the third year, proportion of the inventors are native-born library supported by our Patent Office and instead of being merely a the distribution of specifications and other ocean" is often the ocean itself. On the grants. At all events, it is clear that 1 out on the manu- even Massachusetts would not show so publications to the libraries of the principal other side of the picture, there are many of every 403 of the inhabitants is not a towns, are of the greatest value, and necessarily patents taken out for the mere trade advan- capitalist, and that without low patent fees cost a considerable sum of money; but it is tage of the word "patent only just that the revenues of the Patent factured article-these are sometimes not remarkable a production of inventors. Office should be sufficient to cover such even actual patents, but are simple "applilegitimate expenditures, though it is doubt- cations" on which the stamp of £5 has been proful whether anything more than a working paid for the assumed right to use the word surplus should be allowed to accumulate. patent. In any Act which may be passed As soon as we leave the fundamental prin- this practice will, in all probability, be ciple of a patent law, and study the working hibited; but many firms will pay the full OF late years the sale of scroll-saws and 66 of the actual laws, we find ourselves in a stamp duties, without the remotest inten- VOL. XXXII.-NO. 832. SCROLL SAWING CUTTING. fret cutting The AND FRET machines amongst amateurs has developed in a somewhat extraordinary manner, probably owing to the ease with which the work can be accom |