OTICE TO READER lUmp on Uiii b* pUc«t in ibfl himd* ui oui tv\- di>t* or (Ulort ^atirml \a procvrrf k NO WRAPPING—NO ADORED 8-0 7 JAN j,^2ocTs. nO' Electrical Experimenter I.AROEST CIRCULATION OF ANY ELECTRICAL PUBLICATION JT — — — BE A CERTIFICATED ELECTRICIAN YOU MEN The country needs more trained, graduate LiISXEN electricians. Thousands have gone into the Govern- ment service and there is such an unusual demand for competent electrical men that I am making a wonder- ful offer at this time. HERE IS YOUR OPPORTU- NITY! I want to send you my splendid offer now. Don't hesitate because of age or experience. Young men, boys and old men must now fill the gaps and keep business going. DO YOUR PART. Pre- pare yourself for a real position, by my Home Study Course in Practical Electricity. I am Chief Engineer of the Chicago Engineering Works. I have trained thousands of men and can help you better than anybody else. We also have large, splendidly-equipped shops where you can come at any time for special instruction without charge. No other correspondence school can give you this. SPECL\L OFFER : Right now I am giving a big, valuable surprise that I cannot e.xplain here, to every student who answers this ad. Write today! H622 to n0022 a Week Go after some real money. Qualify for one of the thousands of splendid positions open. All you need to start is a few months snappy, prac- tical '\r\%XXMQ.\\ox\{xov!\ 2, ZQm^tXs.x\\.tn%\Vittx. Come to me NOW. I'll give you mv personal care to ensure rapid and efficient progress. My course is intensely practical. It is highly condensed, simplified, up-to-date and complete. I am so sure you will make a splendid success in this study, that I will Guarantee Under Bond to return to you every cent paid for tuition, if you are not entirely satisfied when you receive your Electrician's Certificate granted you as a gradu- ate of my school. FREE—Lessons and Outfit—FREE Send me the Free Outfit Coupon at once. Do it now! For a limited period I am making a slashing cut in the cost of tuition, and giving each new student a grand outfit of Electrical Tools, Material and Instruments—in addition Abso- lutely Free. I will also send you— free and fully prepaid—Proof Lessons to show you how easily you can be trained at home to enter this great profession, by means of my new, revised and original system of mail instruction. Use this ^*'Free Outfit" Coupon ACT PROMPTLY CHJEF ENG. COdltE, Dept. 2b Get the full benefit of this great offer. Send the 441 Cass St/, CHICAGO, ILL. Coupon or a postal for free information without delay. Do Sir: Send at once fully prepaid and entirely free—complete it now—before my free offers and guarantee are withdrawn. particulars your 'of great offer ior this month. CHIEF ENGINEER COOKE ..p..,. .....\:.': Address Chicago Engineering Works DEPT. 21 441 Cass Street CHICAGO, ILL. k Vou benefit by mentioninff the "Electrical Experimenter' when writing to advertisers. ' : 1919 January, ELECTRICAL EXPERIMENTER 601 Bigger Pay for YOU '*See them You Can Now Knov\r first-pay afterwards * ELECTRICITY As Experts Know It Small When we observe the ever-increasing applications and usages of Monthly electricity, we wonder if all the present openings and the newly created positions in Payment the electrical world can ever be filled. if you Ve The ending of the war lends a new and mighty impetus to the electrical end satis- of American industries. Salaries are soaring. There is practically no Hmit to the earning power of the man fied who educates himself in the finer points of electrical work. Actual working facts With the advent of the new Library of Practical Electricity by Terrell Croft, a new era is marked in the production of self educational electrical literature. This library satisfies a demand never heretofore met—the demand for a home study course which would bring out in detail the actual workmg facts. This great undertaking has been accom- plished. It IS a seven-year task completed. No previous electrical training necessary Three thousand I pages, with twenty-one hundred of the clearest illustrations ever put into book form. Each of the eight volumes is indexed so that everything you want to know about electricity is at the finger's end. And when you hnd what you want, there is not merely a short question and a short answer. You are told everything you want to know. The explanation is clear to you, regardless of whether you have had a previous knowledge of electricitv or not. -' Know electricity as the highest paid engineers know it When you are studying the Croft Library of Practical Electricity, you are studying elec- tricity as experts know it. You are acquaint- ing yourself with the methods employed by the highest paid electrical workers and en- gineers 8 Vols. in America. This Library of eight volumes Flexible sent binding to you FREE for] 10 days' trial So Pocket positive are we that you will be pleased with size Croft Library the of Practical Electricity that we offer to send the entire ten volumes for ten days' free use AU you need do In order to have the books ^ 3000 sent, charges prepaid. Q Is to flu out the attached coupon pages and return to us. Keep the books ten full days. Then If you are not satisfied return them at our expense. If On the other 2100 hand, if you find that they will help you, as they are vo helping thou- illustrations sands of others, send us the small ^ McGraw-Hill Bum of $2 per month for eight Book Co., Inc. McGraw-Hill months. 239 W. 39th St A letter that Book Company, Inc- NEW YORK 239^oi> Westv»e»i 39thoBin atreet,Street, Newl\ew York, N. Y. means something cROFrls^vFwV'.BS.o'if'^t'.i^ "p'"= myseif about ^^^ UBRARY OF PRACTICAL ELECTRIC- Oentlemen X . "'^.r-A? , haveu never tO every man m ' seen and do not believe there was ACT Please send me ttie Li- P''.""*'' .'"•'« English language, a brary of Practical Elec- L • ^^!j: more com- tricity (ahlpplng charges A^ Preheniuve .et of books. It is a library pre- America who is that is just as pai{J). .for 10 days' free eram- ""vice as to the expert, laation. because it is NOW If satisfactory, I will all pracUce interested in send $2- In ten days and $2 per Respectfully, month, until $16 has been paid. If not wanted I -'H iir"-- rn fin m n electricity ^^^ " PEIFER. shipping ru- , n . c... ^ Chief, Doplan SUk Corporation, Hazleton Pa Home City and StAte.. 239 West 39th Street, New York, N.Y. Name of Employer His Address Tour Position You benefit by mentioning the ''Electrical Experimenter" when tvriHno to advertisers ctrical 233 FULTON STREET, NEW YORK Puhlisht by Experimenter Publishing Company, Inc. (H. Gemsback, President; S. Gernsback, Treasurer;) 233 Fulton Street. New York Vol. VI Whole No. 69 JANUARY, 1919 No. 9 SMOKE BARRAGE SAVES ESCAPING 'PLANE Front Cover POPULAR ASTRONOMY—GIANT JUPITER AND HIS NINE From a painting by George Wall. MOONS By Isabel M. Lewis 620 AMERICAN DESTROYERS THROW DEPTH "BOMB BARRAGE" 605 NIKOLA TESLA TO WRITE "MY INVENTIONS" FOR "ELEC- SOLAR ENGINE USES SUN'S ENERGY 607 TRICAL EXPERIMENTER" READERS 622 ELECTRIC DEATH TRAPS IN HUN'S RETREAT NEW PROPOSED WIRELESS BILL AND DISCUSSION 624 Bv H. Winfield Secor 608 IN WITH SUR- EXPERIMENTAL PHYSICS — ELECTRICAL CONDUCTION SUBMARINES PEACE TIME—WHAT TO' DO THRU GASES By John Furia, A.B., M.A. 626 RENDERED U-BOATS 610 J. TELEPHONING FROM MOVING TRAINS 610 MY RADIO "STATIC ELIMINATOR" By Dr. Nikola Tesla 627 SMOKE BARRAGE SAVES ESCAPING 'PLANE 612 RADIOTELEPHONE GUIDED U. S. FLYERS MANY MILES "THE LONG DASH"—A WIRELESS GUN SHOW 613 AWAY 629 AN ALL-ELECTRIC HOT AIR BALLOON 614 THE MANUFACTURE OF VACUUM DETECTORS. THE CITY OF SPLENDID NIGHT By Amos Stote 615 Bv O. B. Moorehead. 630 "ODD PHOTO" PRIZE CONTEST—A GALAXY OF WORLD- A VERTICAL CABINET TYPE COUPLER.. By Joseph H. Kraus, Jr. 631 BEATERS 616 BUILDING A 3-INCH SPARK STATIC MACHINE. ELECTRICAL DENTAL AUTO FOR UPTON SOLDIERS 617 By Dr. E. Bade 633 NEW BRITISH 'PLANE COASTS 20 MILES TO SAFETY 617 A 2S-INCH MODEL GYRO-ELECTRIC DESTROY'^ER—HOW I NEW FLASHLIGHT CUTS OFF AFTER ONE MINUTE 618 BUILT IT 6i4 FOOLING THE DRAFT BOARD?—IT CANT BE DONE 618 EXPERIMENTS IN RADIO-ACTIVITY—PART I—IONIZATION. 636 WINTERTIME USES FOR ELECTRIC FANS.. By Pauline Ginsberg 619 EXPERIMENTAL MECHANICS—LESSON IX. By Samuel D, Cohen 63J ctirk mu€ ^^^iERE are many different ways of produc- tions of a diafram are very great and while it is pos- 1 'S57i I i„g music, and as our culture advances the sible to obtain a single pure note, it is a different mat- desire for better and still better music ter where several pure notes in different octaves are becomes a craving of civilization. From to be reproduced simultaneously. the ancient tom-tom to a Stradivarius vio- lin is a long cry, and the chances are that A way out is suggested by the writer by pressing into as our musical tastes become more refined, service the thermo-telephone which employs no diafram still better instruments will become necessary and highly at all, but uses a very fine platinum wire of microscopic desirable. cross-section. This platinum wire, heating and cooling in unison with the electrical vibrations, imprest upon There are few instruments giving a more mellow and it imparts these impulses to the surrounding air.