BROADCAST 25 Cents WRNYSTATION J XP£RIMENTE`R PUBLISHING COMPANY 230 'FIFTH AVENUE. NEW. YORK Get Winter Reception in Summer with Astounding Successful GROUND ANTENNA Clearer Ground Wave Reception Allows Greater Distance Hundreds of satisfied users of the sensational Ground Antenna-Aer-O-Liminator-are wondering how they ever got along without it. All over the country radio owners are finding marvelous satis- faction in freedom from static and noise interference. This revolutionary improvement of reception comes from hooking your receiver to Ground Wave Reception. Radio engineers tell you that the broadcast wave through the ground is in most cases almost static -free, and with rare exception carries J no noise interference. Read Proof! "I have tested and thoroughly spprove Natural Tone-Better Selectivity the Aer-)-Llminator. I and it increases selectivity and volume without distor- The rapidly increasing army of Aer-O-Liminator owners also enjoy and tion, practically eliminates static, gives appreciate the natural human gush, clear tones, both un local and tone and clarity of this Ground Wave distant stations. Reception. If you haven't tried it you can't imagine the difference! I would recommend the use of Another advantage users have Aer-(l-Llnlnatur to every radio owner found with Aer-O-Liminator is the to get the best reception from his set." surprising DX they get. Distant stations formerly drowned out by static JOHN E. CHRIST4:NSEN or noise interference of air waves now come in clear as a bell. (Radio Engineer.) Selectivity is improved because, with pure, clear Ground Wave Reception, you can . pick up and log signals that before were lost in the jumble of shrieks and howls so common in "There's no such thing as static DX reception through air waves. trouble since I got my Aer-O-l.1minatur. You shouldn't deprive yourself of the new thrill of pure, clear ground wave I get stations I never got befon- nu reception loud and clear I would almost swear a day longer than necessary. We let you prove it for yourself. they were in the nest room." R. (rR'rls, Ipinols. FREE TRIAL Make This Thrilling Test At Our Risk ! Install an Aer-O-Liminator (Ground Antenna). Leave your old overhead aerial up. Try out on a night when static is bad. If you do not get a wonderful improvement in freedom from static, greater selectivity and clear, sweet tone without interfering noises, if you can't get good recep- tions on stations that are drowned out by static on your roof aerial, you EASY TO INSTALL need not pay us a red cent for this test! Send coupon at once for scientific .lust dig a small hole of Aer-O-Liminator about f luehes In diam- explanation (Ground Antenna), proof of performance, eter and drop Aer-t t- and our conclusive iron -bound guarantee and remarkable Free Trial l.iniinator Into it. Offer-Mail CouponAeYwOLirninator TODAY! (Ground MFG. COMPANY, Antenna) CURTAN 154 E. Erle St., Dept. 863-K.A., Chicago. Ill. Passed by Please send me at once complete description of the National Board of Fire Underwriters. Meets Aer-(1-Liminator, with details of guarantee, Scientific Proof, and Free Trial Offer. requirements of the National Electrical Code. Endorsed by Foremost Engineers Name and Dealers. Address City CURTAN MFG. COMPANY Dept. 863-K.A. 154 East r State a-mmi Erie St. Chicago, Ill. Science and Invention for July, 1928 193 Training Employment PREPARING FINDING you you to fill a fine the better -paid Drafting job at position and PLACING you a substantial in it, or money raise in pay . refunded ... r An` \. and orne ro of Position ra ntee ;. Gttara Increased PaY Men who can read blue -prints and draw plans are "sitting pretty" these days. No wonder, when you consider that every machine, every building, all .... -s vq industrial activities start on the Drafting table! Intensive production, record -break- 1`VEGU.4RAN.af d:tU atter T°....u 6o oa;n+ng''n f h e ing construction operations, have created a great demand for expert Draftsmen nr} twiee r nrsc n capable of designing and calculating original plans. Dr,iúns And, further, d at `dd "n; red,a A iru E y$50 1$125 to Expert Draftsmen WEGUARt f at 1ca' vonr prc cnt to a week paid d ño Get this point-that Drafting isn't just one line of work-it reaches out DO u m0 SO. necni rcann,oa into the Electrical, Manufacturing, Building Construction, Automotive , medrrad,isttutnia nS why you'll find well -paid Drafting eP ald fn and Structural industries. That is positions advertised in all industrial centers of the U. S. 70,000 vacancies O~ reported in the past 12 months. And that is why I advise men to go into Drafting, particularly if handicapped by lack of high-school or college education. Today you are in competition with high-school and college graduates for the better -paid jobs. You must have specialized training to win. A Drafting Job GUARANTEED The Entering Wedge to Success paying 50% more than you earn today in all Building and Manufacturing Lines -or not a penny of cost! I recommend Drafting, too, because it can be QUICKLY learned at home, in spare time-with- out quitting your job, without losing a day's time or a dollar in pay. Because you're sure there Now, at a cost you can afford, on terms of only will be a good position waiting when you are ready for it. And because the work is so fascinat- $6 per month, you can actually BUY a fine ing and offers better-than -ordinary chances for advancement. For the Draftsman is in close con- Drafting position and a substantial increase in tact with important work and BIG MEN, and he is right in line for promotion to Superintendent and other executive positions. pay. A million -dollar institution guarantees both-the training, then the employment. Under money -back penalty. This agreement brings you your SECOND Lessons CHANCE. To repair a neglected education, to specialize, to change to a line where you can get actuailyFREE!Drafting ahead more rapidly. Read it, and investigate it! The American School to prove you can learn at Chartered 30 years as an EDUCATIONAL in- home, in your spare time! stitution and like the best resident schools and colleges, conducted NOT FOR PROFIT. We You will never have a more seri- offer complete, thorough up-to-date instruc- ous personal problem than decid- tion, built by 200 leading Educators, Engi- ing your future life-work-so we neers and Execu- merely urge you to LOOK INTO tives. A unique in- Drafting. See how you like it, see if you learn as struction, built to readily as most men do, get the facts about the op- meet the specifica- portunities, the salaries paid, the jobs open, the tions of well- paid chances for promotion. jobs as laid down This is why, on receipt by employers them- of your name, we will selves, yet simplified for send you the first three ready understanding by lessons of our Drafting men with only common course without cost or schooling. obligation. And we are the first in the home study field to recog- nize the need of giving a COM- PLETE SERVICE to ambitious men O. C. MILLER, Director Extension Work. -training, pear employment. Which THE AMERICAN takes you as you are, supplies the SCHOOL, 0. C. MILLER Dept. DB -294 Drexel Ave. Director Extension Work equipment you lack, and lands you & 58th St., in the better job you seek. Without Chicago. Illinois risk to you! Please send without cost or obligation: I, Three Drafting Lessons. 2. Facts about the opportunities in Drafting. 3. Your Guarantee to train and place me under money-back penalty. r.nPAc1r1 je Cild301. Name Address Dept. DB -294 Drexel Ave. & 58th St. ,Chicago. Ili. Age Occupation 02) I, vvaoo. 4.Dovo,,,,, ;1'i%:`i-il 4'''' 4;.,rí I I ellet %'ji ,AiIIÌ i ention Formerly ELECTRICAL EXPERIMENTER COMBINED WITH "THE EXPERIMENTER" EDITORIAL, ADVERTISING AND GENERAL OFFICES: Voi. XVI 230 Fifth Avenue, New York City Whole No. 183 Published by Experimenter Publishing Company, Inc. (H. Gernsback, Pres.: S. Gernsback, Vice-Pres. and Treas.; C, E. Rosenfelt, Sec'Y. ''ti:umuu% Publishers of SCIENCE AND INVENTION, RADIO NEWS, RADIO LISTENERS' GUIDE, AMAZING STORIES and FRENCH HUMOR Editorial Staff Contributing Editors Il UGO GERNSBACK, Editor -in -Chief. Astronomy- /lutomottve Subjects- George A. Luers Peck, Herbert Hayden. II, WINFIELD SECOR, Managing Editor. Dr. Donald H. Menzel, Ph.D., Lick Observatory; Radio- A. P. W. J. Lugten, of the Harvard College Ohsery story. Magic and Psychic Phenomena- C. O'CONOR SLOANE, PH. D., Entomology and Allied Subjects- Joseph Dunninger, Joseph F. Rinn, Edward Merlin. Associate Editor Dr. Ernest Bade, Ph.D. Foreign Correspondents- JOSEPH Physics- Dr. Alfred Gradenwitz, Germany; Dr. H. Becher. II. KRAUS, Field Editor. S. Leonard Bas- PAUL WELKER, Dr. Harold F. Richards, Ph.D., Ernest IC. Chapin, Germany; C. A. Oldroyd, England; Radio Editor. M.A., Dr. Donald H. Menzel, Ph.D. tin, England; Count A. N. Mirzaoff. France; Hubert S. GERNSBACK. Wrinkles Editor. Chemistry- Slouka, Czecho-Slovakia; P, C. van Petegem, Hol- \V. J. ROMAINE, Art Director. Raymond B. Wailes, Dr. Ernest Bade, Ph.D. land; Richard Neumann, Austria. IN AUGUST ISSUE CONTENTS OF THIS NUMBER 250 Animal Superstitions GENERAL SCIENCE The Oracle 266 L. Ditmars, cur- Editorial 199 Patent Advice Mr. Raymond By Hugo Gernsback of mammals and reptiles, CHEMISTRY ator Our Spiritualistic Investigations 200 Experimental Chemistry and Electrics 234 New York Zoological Park, By Joseph H.