The Electrical experimenter

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816 ELECTRICAL EXPERIMENTER April, 1918 IN The Dictograph in the Trenches our November, 1917, issue Mr. H. Gernsback showed graphically how the microphone could be used for trench warfare, and we showed several applications how it was to be accomplished. While the article was not official in any way and only showed the application as it existed in our minds, we are now happy to show actual photographs of the same idea, showing that the idea is now in actual use on the front, the strange part being that the several applications are exactly as shown by us in our article, which like many similar ones was only imaginary, we having no official information of any kind that the microphoneposes. was being used for such pur- Our photographs show the dictograph at the front, and how our boys "over there" use the instrument to detect plans of the enemy. Illustration No. 1 shows one of the boys crawling up towards the enemy trench to place a highly sensitive transmitter. It will be noted that the transmitter is placed upright in an old tomato can which easily camouflages the sensitive little instrument. As is well known these microphones are so sensi- necessary for him to lie perfectly still for perhaps hours at a time, as the slightest movement would draw machine gun or sharp rifle fire at once. When finally the man in "no man's land" retraces his course, he must do so very slowly and cautiously, going backwards at the rate of fractions of an inch at a time, irrespective of the fact that it may be freezing or that the rain may come down in torrents. However, this is only one of the disagreeable fortunes is then sprayed with finely divided metallic powders. The metallic particles are thus driven into the surface of the glass and a very durable metallic coating ensues. It is stated that when the under surface of the glass flask is treated with copper or aluminum in this way the water can be raised to boiling point in three-quarters of the time that would otherwise be necessary', and, in addition, the vessel is much less liable to crack. One would imagine that this process would have useful applications for treatment of glass reflectors for lighting purposes. The instrument known as the dictograph employs a super-sensitive microphone connected with a telephone receiver and battery. The microphone converts the sound waves into corresponding electrical currents variations, which operate the receiver. INVENTOR CALLED BY U. S. TO FINISH U-BOAT DEVICE. Experimenting for a year with an invention aiming at the destruction of submarines, Prof. Harvey C. Hayes, head of the physics department of Swarthmore College, has been so successful that he has received a call from Photos Western Newspaper Union How Our Boys "Over There" Listen in for Fr itz's Secret Confabs. A Super-Sensitive Telephone— Known as a "Dictograph"— Is Used For This Purpose. Fig. 1, Shows a "Sammie" Craw ling Up Near An Enemy Trench to "Place" a Camouflaged Microphone (in a Tomato Can); Fig. 2, How the Dictograph Transmitter i tive that they detect a whisper at a distance of fifty feet. The sensitivity too is increased a great deal if the wind blows towards the microphone. Fig. 2 shows how one of the microphones is placed near the enemy trench in a sort of dug-out, but little ground separating the microphone from the trench. This is right under the enemy's parapet. In Fig. 3 a trench receiving station is clearly shown. At this station the intelligence is received by one or more operators, usually one listening, the other writing down whatever talk is picked up. It goes without saying that the successful placing of these detectaphones as well as the laying of the wire, which operations are always under direct fire of the enemy, is one of the most dangerous and difficult undertakings in modern warfare. It is a task allowed only to a man of iron nerve, and it takes much courage and good judgment not to blunder. During the night very often the presence of a man is detected, and it then becomes s Placed in a Dug-Out Near an Enemy Trench; Fig. 3. A Trench "Listening Station." of war, and our boys do the work as cheerfullv as thev do it efficiently. WHITE HOUSE ELECTRICITY. The White House at Washington is said to have the most intricate and complete electrical system installed in any building in the United States. There are in the mansion nearly 170 miles of wires, providing for 3,000 incandescent lights, a bell system, and a private telephone system for the President and his family exclusively. NEW METHOD OF MAKING LEY- DEN JARS AND CONDENSERS. Long ago the tinfoil type of Leyden jar and condenser for wireless telegraphy and other purposes passed into oblivion, and in its place settled the copper-plated type. A new method of producing metal-coated glass for such purposes is described in Glashiitte, which, it appears, is a variation of the Schoop process. According to this method the surface of the glass is heated until it just begins to soften and the surface the United States Government to enter the national service. He refused to discuss particulars of his new venture adding that he has been forbidden to disclosed the location of the laboratory' where he is to continue his research work. Professor Hayes will be joined by five other physicists from the best universities and laboratories in the country in the Government research work. They commenced work on January 1. Professor Hayes expects to be engaged in this service for a year at least, and it is unlikely that he will return to Swarthmore at the opening of the next term in September. His family will accompany him to the site of the laboratory'- Professor Hayes was in his fourth year as a member of the faculty of Swarthmore College. Previous to his service in the physics department he was an instructor in research work at Harvard, where he took his doctor's degree. The vacancy caused by Professor Hayes' withdrawal will be filled by W. O. Sawtelle. of Harvard.
April, 1918 ELECTRICAL EXPERIMENTER 817 "Electro-Magnetic Log" that Measures Ships Speed TALK to any old-time jack tar or sailorman as to how they measure the velocitj or speed of a ship when under way, and he will cut loose with a long tirade on the various merits and demerits of the immortal taffrail log— famed in song and story the world around. For the taffrail, be it known, gentle reader, is the hindermost deck rail on a ship, while the log line is the rope or cable which is heaved over said rail and into the briny billows below whenever the cocky commodore wishes to know how many knots the mechanisms used extensively on large and s.nall vessels leave something to be desired. They are not as simple or as accurate as they should be. Realizing these facts, two Boston inventors—Messrs. Smith and Slepian—have worked out a very ingenious and extremely simple electro-magnetic ship's log which is illustrated herewith, both in detail and applied to a ship. It's principal feature is that it does away with all dangling thingmabobs suspended from ropes or cables, and which devices, owing to this fact, are exposed to the water : Fig. 2 is a longitudinal section of the magnetic device, while Fig. 3 is a wiring diagram of the electrical connections to the meter calibrated to read knots per hour, and Fig. 4 shows the distribution of the magnetic flux and the direction of the induced E. M. F. In the illustrated embodiment of the invention the magnetic flux is furnished by a permanent magnet, having a middle pole N and two side poles S. The magnet poles are long and narrow. The magnet is arranged permanently in the ship's bottom FIG.I ELECTRIC LOC, OR SHIP'S SPEEO INDICATOR BOARD F0RBRID6E FIG.2 ELECTRODES FI&.3 KNOTS PER HOUR MITER FI&.4 ELECTRICCABLES TO BATTERY AMD XO&'APPARATUS MAGNETIC FLUX LIMES IN WATER Copyright by E. P. Co. Every Yachtsman and Sailor Knows What the "Log Line" Is— It Measures the Speed of a Vessel Thru the Water by means of a Spinning Propeller Attached to Its Lower Extremity, Which Connects With a Dial Device at the Taffrail. Errors Are Liable at Any Time, Especially When the Observer Is Inexperienced. Here's the Latest—a pure "Electrical Log" Which Is as Rugged as It Is Simple. It has no moving Parts and Is Built Flush With the Hull. good ship is making. And how does the faithful mate take the log? Well, it's this way. fellow land-lubbers As aforementioned, the log line is thrown over the taffrail and into the water. At the lower extremity of the line there is secured a propeller-like device which spins around at a speed proportional to the speed which the ship is making thru the water. The revolutions which the little propeller makes are transmitted to the deck rail by virtue of a flexible shaft, which connects with a dial and indicating arrangement, whereby it becomes readily possible, with the aid of a stop-watch, or by other means, to determine how many revolutions per minute the log By referring to propeller is revolving at. tables and other data provided for the purpose, it thus becomes possible to find out how many knots you are making. But this is a round-about way of doing it. Even the new electrical log : always subject to more or less error. This new electro-magnetic log is a fixture, once installed on a vessel ; there are no protruding parts to be knocked off or damaged, and the indicating instrument reads off the ship's speed directly and accurately in knots or miles per hour. Here is the way in which the new electro- A magnet is magnetic ship's log works : placed on the ship's bottom so that the magnetic flux passes thru the sea water. The magnetic flux traveling with the ship thru the water generates a difference ot electric potential in the water directly proportional to the velocity of the ship. These differences of electric potential are measured and from them the speed of the ship is determined. In the drawings which illustrate the detailed construction of the invention. Fig. 1 is a perspective view of the inclosed magnet and electrodes, the lower face of which is so that the lower face of the magnet is next to the water. The magnet is insulated from the ship's bottom and the lower face of the magnet is insulated from the water by a plate of insulating material. The ends of the magnets are closed by plates of nonmagnetic material. In the cavities and between the poles of the magnet are located two electrodes of amalgamated zinc. The cavities around the zinc electrodes are packed with zinc sulfat and the cavities are lined with insulated linings. In the insulating plate are plates or windows of porous earthenware thru which the water can seep, to form an electrical connection between the sea water and the zinc electrodes in the cavities. While the porous earthenware windows allow an electrical connection thru them, they do prevent any considerable diffusion thru them of the zinc sulfat so that the (Continued on page 863)
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