Kindly keep your queries on separate sheets of paper when corresponding about such matters as patents subscriptions. books etc. This will greatly facilitate answering your questions, as in many cases they have to be reffered to experts. The full name and address should be given on every sheet. No attention will be paid to nnsigned queries. Fuji hints to correspondents are printed from time to time and will be mailed on request. (12572) S. B. asks: If a meter were attached to the wire or a five-horse motor, and tbe current (500 volts) turned on for, say, one hour, funning only single lllOtO!, would it use as mucb juice in one hour as if the motor were doing full five horses' work? A. If a lve borse-power electric motor is run without load, it will only require the current to turn it whieh is able to overcome the friction of the parts of tbe motor. If full load is put upon the motor, it will tben require five borse-power to turn it. This is exactly the same as any other machine, a grindstone, for instance. A boy can turn it swiftly when there is nothing grinding upon it; but if a man holds a scythe upon it, bearing down with all his force, even a man might not be able to keep the stone in motion. Power must be furnished to any machine in proportion to the work called for from the machine. (12573) G. W. M. asks: 1. What are the chemical elements found in the atmospbere? Is there any chemical change wben subjected to heat' A. Atmospheric air is made up of 21 per cent of oxygen, 78 per cent of nitrogen, about 1 per cent of argon, and a minute trace of belium, xenon, neon, krypton, hydrogen. No chemical change is produced by simply heating the air to any moderate degree, unless some other substance is present which can be burned with the oxygen. At the tempera lure of tbe electric arc the nitrogen and oxygen combine and form nitric and nitrous oxides. 2. How is commercial oxygen, used in medical science, produc(d? A. Oxygen for industrial and medical purposes is made from chloratc of potash or from binoxide of sodium. The' former is heated in a retort with manganese dioxide, and the latter is simply dropped into water. (12574) E. J. L. asks: WiII it be too much bother to advise me the numher of cubic feet in a perch of stone? Tbe di< tionary and printed authorities all seem to agree on 24%, but masons here claim that there are only 16% A. A “vereh” of masonry is not a lleasure whose value is everywhrre tbe same. It seems to be usually 1t '2 fcet long and 1 % by 1 foot, which would make it contain 24 % cubic feet. It is often tahrn at 25 cubic feet. b” * has other values in different places. If all such peculiar measures could he dropped and our work measured in feet. yards, etc., it would greatly simplify matters. (12575) J. B. C. asks how to oxidiz( silver. A. 1. Add four or five thousandths ammoniulIJ sulphide or potassium sulphide to water at a temperature of 160 to 180 degTees Fahrenheit. ''hen the articles are dipped into this solution an iridescent coating of silver sulphide is produced, which, after a few seconds, turns blue black if allowed to remain in the liquid. Remove, rinse, scratch-brnsh, and burnish when desired. 2. 'bere are two distinct shades in use, one produced by a chloride, which has a brownish tint. and the otber by sulphur, which bas a. bluish-black tint.. To produce the former it is only necessary to wash the article with a solution of sal ammoniac (ammoninm chloridf). 3. A much more beautiful tint may be obtained by employing a solution composed of equal parts of copper sulphate and ammonium chloride in vinegar (or dilute acetic acid). The fine black tint may be produced by a slightly warm solution of sodium or potassium sulphide. 4. Bromine, f gr.; potassium bromide, 5 dwt.; water, 10 oz.; boil the silver in this usually 2 to 5 minutes. then polish with rouge. 5. Dissolve sulphate of copper, 2 dwt.; nitrate of potash, 1 dwt.; ·ammonium chloride, 2 dwt., in a little acetic acid. Warm the article and apply the solution with a camel's hair pencil and expose to the fumes of sulphur in a closed box. Parts not to be colored must be coated witb wax. 6. Dip the clean silver article in a solution of sulphide of potassium (liver of sulphur), 2 dr. to 1 pt. of water. Heat this solution to a temperature of 175 degrees Fahrenheit. Immerse for a few seconds only, when the article becomes blue black. For a velvet black, dip the article, previous to oxidizing, in a solution of mercurons nitrate and water, and rinse. Then dip in tbe sulohide solution as above. For a brown shade, oxidize the potassinm sulpbide as above, then dip in a liquid composed of 10 parts of blue vitriol and 5 parts of sal ammoniac to 100 parts of vinegar. After oxidation, hrush with a scratch brnsh very lightly. to brighten and variegate the surface. There arl many other methods, among which will be found the following: 7. Expose to the vapor of chlorine. 8. Use a solution of equal parts of copper sulphate and ammonium chloride dissolved in vinegar. WateWan's Ideal IburftSftPeii Always Acceptable | W ATERMAN'S IDEAL is one of the very few gifts which the rec eiver can put right in pocket :r p urse for constant u se. If e ver yone had th e selecting of th eir own Christmas presents this is the kind that would be purchased. As a gift to anyone, or for yourself, there is not another article that shows better purchasing discretion than Waterman's Ideal Fountain Pen - it is a compliment to your taste. This pen is made in a very wide range of sizes and styles in order that the pen technique of every writer may be individually suited . Your selection may be exchanged until satisfactory. Whether you buy a plain Waterman's Ideal or one studded with diamonds, the quality is of that same successful standard which the careful workmanship and Waterman patents have brought to continued perfection. This is the gift for people who are hard to suit. From Stationers, Jewelers, etc_ Standard, Safety and Self-Filling Types. Icold SlIbJlitlleJ. Smd for Gii Book. frs/rnu-e/i tsi J ok. ^C L.E.Watet-man CoJ73BK<radway,N.Y I 8 School St.. Boston; 115 So. Clark St., Chicago; 17 Stockton St., San Francisco; 107 Notre Dame St.,W ., I Montreal: Kingsway. London : 6 Rue de Hanovre, Pari.. 54' SCIENTIFIC AMERICAN December 9, 191 1 THE STANDARD RAILROAD OF AMERICA Railroads are known by the service they render. The PENNSYLVANIA RAILROAD has gained its title by always giving its patrons the best that can be provided-the best kept and protected roadbed and track, the newest steel equipment, the most satisfactory dining car service, and the fastest time consistent with safety. Its standard is exemplified in the "Pennsylvania Special" which makes the less than 18-hour run between New York and Chicago with clock-like regularity. Leaves NeW York - - - 4.00 P. M. Arrives at Chicago - - - 8.55 A. M. Leaves Chicago ... 2.45 P. M. Arrives NeW York - - - 9.40 A. M. The New York portal to this splendid service is the Pennsylvania Station one block from Broadway at 32d Street, which typifies by its simple grandeur the excellence and high character of Pennsylvania Railroad service throughout. THE EDISON CONCRETE HOUSE C *IH; it is constructed, :: much it !ill cost, i: it pr:ctical f;om an :;chitectural and engineering standpoint? These and other important questions relating to the structure are discussed i n a good, thorough. illustrated article pubhshed in Scientific A merican Supplement 1685. Price 10 cents by mail. Order from your newsdealer or from MUNN&COMPANY. Inc. 'Publishers 361 Broadway, New York ONLY $36. With ou 00 ' he Wonderful lilt IT LANTERN our Improved famous ALCO RADIANT LIGHT new 1912 Model haf lllaIlY improvements and double brilliancy. Write for illustrated circular of this :tlld Lanterns of all styles and lights at bottom prices. IF YOU O"N A IANTERN we should have your name to lail t o you our regular announcements of new slide and lecture set1. *75,000 Lantern Slidesto rent. POST CARD MAGIC I.ANTERN reAec tf im a g e of p o st ca rd or any EngRneerWNng, Microscope, Optical, Scientif S C, Photo, Lantern Slide Supplies Here's the Pile that Never Fails whenjou want Correspondence Quick J LTO It's the nearest fool-proof-nearest careless· clerk·proof filing cabinet ever devised. It's easier to file correspondence Quicker, and more accurately in a Multoplex Cabinet, because the drawers have InSIde Metal Adjustable ParItIOns. 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Write for the book today, mentioning your fr Dame and in What capacIty you serve. "Inventors and Inventions" A NEW BOOK JUST PUBLISHED BY H. ROBINSON 41 W. 33d ST., NEW YORK. INDISPENSABLF AND INTERESTING TO EVERY INVENTOR OR PROSPECTIVE INVENTOR. PROfUSELY ILLUSTRATED CLOTH BOl'ND, $ 1.00. IT TREATS AUTHORITATIVELY IN A CLEAR, POPULAR AND ENTERTAINING STYLE THE fOLLOWING SUBJECTS: How to Invent. financing a New Invention. Marketing a New Invention_ Advice to Inventors_ The Glory of Invention. Pictures of famous Inventors. Various Ways Employedlto Cheat ard Rob Inventors. Present Available Means of Proteding an Invention. Treatment the World accords to Them, and Other Important Subject.. EVERY HOME LIBRARY SHOULD HAVE Stories of Useful Inventions By S E. FOR MAN. author of “A HIstory of the United States.” etc, Sixteen “ t r ue stories,” stories of human progress as shown in man's making of the match, the stove, and other inventions which are most useful to man in his daily life, told to stir and hold the interest of the young reader. MANY PiCTURES. 12rm, 248 PAGFS Price $1.00 net, postage 11 cents Published by THE CENTURY CO. New York We have been asked If we use the name of the subscriber when writing to the people whose names appear on the lists sent in by our friends. Of course we do not mention the name of the person who sent us the list without permission. If this doubt has deterred you from sending us a list don't wait any longer, send in the list at once and rest assured that your wishes regarding the use of yoar name will be respected. All you need do Is simply send us the names of those whom you think the “ Scientific American” will interest and we will do the rest. Of course the more names you send us the better will be the results obtained and the longer the period for which your personal subscription will be extended. For each new subscription received from the list you send us we will extend yoor subscription four months. Thus if we get three subscriptions from your list we will extend your subscription for a full year. Don't fail to put yoar name and address on each list you send us, so that we may be enabled to give proper credit. Mail all lists to Circulation Department, Scientific American, 361 Broadway, New York City. EpS M aglca I A ppara t US. 6—t-9 Grand Book Catalogue. Over 700 e nera .. n •• a5c, Parlor Tricks Catalogue, free. MARTINKA&CO. . !lfrs .. <U3 Sixtb Ave. . New York Learn Watchmaking We teach it thoroughly in us many months as It formeriy took years. ))oes away with tedious apprenticeshlp. :oney earned while studymg. POSitions secured. Easy terms. Send for catalog. ST. LOUIS W A'J'CIIMAKING SCIIOOL, St. Loul., Mo. HUMETtll I NO OR IMBIICA6 S? ANYI” I NG *WIP _________ 118.124 North Clinton !t. C..BfS lVacaftf'.^f^USA Veeder Counters to register rec i proca t1 tI g tnOVemellts or re\·oll 1tions. Cut full size. Booklet Free. VEEDER MFG, CO, 18 Sargeant St., Hartford, Conn. I Cyclometers, Odometers. ^Tachometers. Counters and Fine Oaitinqs . Represented ill Great BrItain by :1 ARUT&Co., LTMI'l'tW, 1 City Road, lillshllr: Sllmlre, London, E. C; France,'by MARTT&Co., LIMITED, 107 Avenue Pm·mEntier, Paris, Germany, Austria-HuIgry am;1. Sc!]:'navi run w. LOEWE&Co.,HntteK St*asse 17-20, BerlIn. Countries by Why not enJOY absolute comfort in your automobile over all klOds of roads' You can accomplish this if your automobIle IS eqUIp ped wah tbe The New 1912 FLENTJE Automatic Hydraulic Jounce&Recoil Preventers in a clsisi hy itself anaoiA “BEST IN T;;J ;[ LD" In a short tlme yoU WIll save lhe cost of the preventers on tires and sprl ngs and engIne and body of your car. Try a set on thirty d ays' free tnal and three years' guaran tee. and be conVinced of the correctness of my claIms. S5000 a side to any sback a b sor be r manufacturer to dis pT9ve that “The Flentle 1 1 is the best In the world. For further particulars, apply to ERNST FLENTJE, 1643 Cambridge St” Cambridge, M .... New York Branch. 1926 B'way, cor. 641h St., Room 400 N. Y. City DectflllwJ 9, J 91 J SCIENTIFIC AMERICAN 543 Inventors! Start a Shop of Your Own Instead of paying some one a profit to furnish power for your small shop or experimental room, buy an I H C Gasoline Engine and start a shop of your own. A small shop, with a lathe, shaper, power hack saw, drill press, emery wheel, and portable forge, can he run at a surprisingly low cost for power when an I H C engine is installed. You can shut the engine down when not needed, cutting off all expense, and can have its full power ready to me within a few seconds after starting it again. Furnish your own dependable power with an I H C Gasoline Engine They are made in all styles and sizes, one of which is just what you will need. All I H C Engines have proved themselves the simplest, strongest, most reliable, most economical, and most durable power outfits made. Let us send you the facts. Write now for catalogue. Read about I H C superiority in design, materrals, and workmanship. Then decide to buy one and furnish your own power. If you wish, we will help you decide on the size and style of engine best suited to your needs. International Harvester Company of America (INCORPORATED) 15 Harvester Building CHICAGO U SA Bu ild Y our Own Motor trom a set of o n r castings. DIot d roeyele, f nrine or Stationa ry. Our finishe o , atta chable o u tfits ft any wh eel. Send stamp for-particul:us. Steffey Mfg. Co_ 2941 W. GIrard Ave. P hiladelphia, Pa. For all Purposes The High Powered, JAeht ~ Weight Cu shin an Engine measures out j ust enough gasoline to do the work required. Advanced 4 cycle type. Weight under 200 lbs. 4 h. p. rating but actually develops over Automatic Throttle Covernor witb High Orad. Schebler Carburetor. ' Easy speed changing is butoneofseveralmarks of superiority. Special friction clutch pulley wIth belt and chain drive. Sold on 10 year guarantee. CUSHMAN MOTOR WORKS, 2070 N. St.JL1ncoln.Neb. Use KEROSENE Engine FREE! Amazinl “DETROIT” lero. sene lnshitped on 15 days' IREE Trial, proves :eros:i; cheapest. safest, most powerful fuel. If satisfied, pay lowest prf!; e!:rgiven ;r;efIe farm engine; if not. pay n othing. Gasoline Going Up! Automobile owners are burning up so much gasoline l h;t tle wOrd?s sJ;r; is running short. Gasoline Is 9c to 15c higher than coal oil. Still goinr up. Two pintsof coal oil do work of rhr': p?nt! gasoli:e. N waste, no evaporation, n o ::plosion from coal gil. Arm aII-n g “ 0 ElR 0 IT" The “DETROIT” is the only engine that handles coal oil sucC:f: ; !y; uses alcohol, gasolin? and benzine, too. Star!! without cranldng. Basic ;!ient—only three movrng parts-no cams-no sprockets-no gears-no valves-the utmost in simplicity,po:er andtength: McOounted on ::ii:!i!i! sizes, 2 'hoh . p., in stock : eeady to stip. Completeenginetested ju:t be f ore crating. Comes all ready to run. Pumps. saws, threshes, churns. s:har::es miik· grinds feed, shells corn, runs home erectric-lighting plant. Prices (stripped), $29.50 up. Sent any place on 15 days' Free Trial. Don't buy an engine !!ll you investt, at Tb a::zi::, money-!::in:i :Z: er-saving “DETROIT.” Thousands in use. losts only postal t: En: out. If you arefirstin your neighborrhood to write, wewill allow * JOU Sp ecial Efxttra -Low Introdu cory p rlcew{i Writewl Detroit Engine Works, 127Bellevue Ave., Detroit, Mich. not carbonize methodical reVISIOn, developing them to include present conditions, and showing the conclusions to be drawn from the three most recent wars in which navies have borne an active part: Japan and China in 1894, United States and Spain in 1898. and Japan and Rnssia in 1904. The contribution of each war to the snbject was considerable, the last named being especially frnitful in furnishing examples of correct and incorrect naval strategy. He shows the principal strategic strongholds existing to-day, tells how the balance of power on the sea is maintained, and how it may be readjusted if Germany continues to increase her navy. IIe takes up the subject of coast defenses, both as protection to the country and as hases of supplies, remarks upon distribution of fleets, and explains the changPR nnd tactics made neCCSRUl',V by recent devicps, such as the wireless. Dpfning naval strategy simply as “the proper use of means to attain euds,” his analysis of the naval events of history from this view-point brings a snbject supposedly technical and difficult within the comprehension of the average reader. COST - KEEPING FOR MANUFACTURING PLANTS. By Sterling H. Bunnell, Ph.B., M.E. New York: D. Appleton&Co., 1911. 8vo.; 233 pp. Price, $3 net. To reach its highest efficiency a manufacturing plant must be watched as a doctor watches a patient. It is the cost-keeping departmpnt that mus' point out the weak spots aud indicate a rtmedy. Without accurate knowledge of weak spots-that is, of instances where the cost of operations exceeds or approximates the Rt1ling price-remedies are mere guess-work, On the other hand, there is so much of compllcation and red tape about many cost-keeping systems tbat manufacturers hesitate to adopt them. Mr. Bunnell, while avoiding in great measure the encumbrances incident to thrse systems, sacrifices nothing of efficiency. He surveys the field of cost-acrounting in a genfral way, gives some valuable counsel on the introduction of an adequate system, and then proceeds to sustain and amplify the general plineiples by reducing them to practical appllcation. All the necessary accounting forms are drawn and their uses explained, so that the routine of cost-keeping may he established with the least amount of labor and worry, and may result in accurate and progressive knowh'dge of vital facts and details. He clearly demonstrates that the efficiency of this department and the prosperity of a business are very closely related. It would be hard to find a more enlightening or sensibly-written work on the subject. MOEDEBECK'S TASCHENBUCH FUR FLUG-TECI-INIKER UND LUFTSCHIFFER. Berlin: Verlag von M. Krayn, 1911. 920 p.; 238 illustrations. It was in 1895 that the late Capt. Moedebeck issued bis admirable aeronautic handbook. When we consider that the dirigible at that time had hardly developed much beyond the experiments of Renard, and that Lilienthal alone had made any experiments in dynamIc fight, we can readily understand how bold an undertaking Moedebeck's was. Yet he carried tbrougb his scheme with good judgment and with such foresight that his book proved a boon when the dirigible really took its place in our daily lives. In the first edition it was almost out of the qnestion to devote much space to the flying machine for the simple reason that the flying machine as we know it did not exist. In the second edition, issued in 1903, the remarkable performances of the dirig ible still took up the major pOl'tion of the book. Unfortunately Capt. Moedebeck was not spared to revise this last edi tion. That task has been intrusted to Prof. Suering, of the Royal Meteorological Observator' at Potsdam. That he has done it ably follows almost as a matter of course from his scientific standing. As it now comes to us, the book is divided into the following cbapters: Gas ('he PhYSical Propelties of Gases and Technology of Gases) ; A tmospheric Physics ; Aerological Observations; Kites and Parachutes ; Balloon Technics ; Navigating a Balloon ; The BaSis of Balloon Navigation ; Practical Aspects of Balloon Navigation ; The History of the Airship ; Airship Construction, Practical and Theoretical; Navigation of Air Vehicles; Animal Flight; Gliding Flight; Technics of Flying; Engines for Airships and Flying Machines ; Aerial Propellers ; Society News ; Tables. ARTISTIC HOMES. By Mabel Tuke Priest-man. New York: A. C. McClurg&Co., 1911. 8vo.; 148 pp.; illustrated. Price, $2 net. There is a steadily increasing appreciation of sensibly-planned and at the same tim2 ar tistically satisfying houses that is encouraging to those of us who wO'ld have America surpass her older rivals in modes of taste as well as in business methods. A home that is pleasing and restful to the eye contributes substantially to the contentment and education of mankind, and costs no more in the long run than many of the pinnacled and castellated atrocities we see around us. The growth of this appreciation of the truly beautiful and usefuI in bore-making has been fostered to no small degree by such works as Mrs. Priest's “Artistic Homes,” in which are described and pictured ideal dwellings visited by her in this country and in England, with concise statements of thlir cost and all the essential details of their construction. , · SFETY Fountpens for Christmas They are made for continuous practical service and for that purpose are unexcelled. The construction is simplicity itself. There are no complicated parts to break or get out of order. The “Ladder Feed” and the “Gold Top Feed” furnish the exact amount of ink required, and automatically prevent Hooding or skipping. The “ Screw Down Cap” creates an ink tight chamber around the pen pomt and renders leaking or sweating absolutely impossible no matter in what position the pen is carried. The nib is of 14 karat gold, tipped with irid10m and is practically wear proof. 39 Made in a variety of Sizes and Styles to suit requirements. For the man who wants a pen for practical work none can equal the .. Swan Safety.” A pen for every purpose. Nibs to suit the requirements of all styles of handwriting. For the Bookkeeper the Posting pen is unexcelled, and for ladies a large assortment in gold and silver is offered. iiWAN may be depended on for years of satisfactory service and on , account of its ab-k solute r eliability J is ini able to the fotnraa PBKi- FOR XMAS A "SWAN" is always an ideal present and one that will recall pleasant memories of the donor for years to come. Sg^ Not a Toy but a real help for busy men and women. Pices. $2.50 and uP. at all Stationers and Jewelers. MABIE, TODD&CO. (The Makers) f* B^J 17 Maiden Lane, New York m^^' 124 York Street, Toronto MANCHESTER PARIS 209 So. State Street, CLicago 79.80 High Holborn. London BRUSSELS SYDNEY The only bond paper whose method of distribution assures you Impressive Stationery at a Usable Price Made in White and SIX Colors WIth E to Match That economical method of distribution is simply sell i ng direct to respon,ible printers and lithographers in 500 lb. lots and upwards, instead of through local jobbers in ream lots to any printer. You save the jobber's profit and the heavy expense of handling small lots if you secure your business stationery on Construction Bond. You can obtain such stationery from the most responsible printers and lithographers in practically every city in the United States -from Boston to Los Angeles and from the Twin Cities to Galveston. Ask us on your business letterhead or card and we'll send you the names of those in your locality and a complimentary portfolio of specimen letterheads on Construction Bond. Other fine bond papers will produce impressive stationery; but only one fine bond - Construction Bond - has the economical method of distribution that assures you Impressive Stationery at a Usable Price. Send your business card for specimen letterheads. W. E. Wroe&CO., 1015 Michigan Ave., Chicago