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Problems of the Vessel eeratd: Listening Devices for Detecting Submarines -- To Train Seamen 4. directed toward the improve- ment of listening devices for detecting submarines. As a result, great advances were made in hydro- phones. The French navy developed a hydrophone known as the Walser gear which embodies two sets of a number of sound receiving plates mounted on two areas which are convex to the sea. One is on each side of the ship's hull near the keel. By this device the sound waves are transmitted to the air inside the ship. The position of the sound focus is determined by means of a _ funnel from the end of which a tube leads to the listener's ear. Ship and water noises seriously in- terefere with the detection of sub- marines but this has been overcome in a measure by towing a directional hydrophone, encased in an artificial "fish" behind a chasing ship. This "fish" is built along stream lines to eliminate noise as much as possible. As the "fish" can be. towed quite a distance behind the vessel, noises from the ship do not reach it. Even though apparatus is perfected for the detection of submarines it will prove useless if the submarine can be made practically noise proof. Even at the present time the range Of 'hearing is not -more than 100 yards in the case of a modern sub- marine traveling at a speed of two to three knots. "One system that appears to be practical involves the use of a beam of sound waves sent out by the chasing ship in much the same man- ner as a. searchlight is used. Thus it is possible to sweep the seas and when a submarine happens to come within range of the beam the sound waves are reflected and echo effects are obtainable. -- To enable vessels to navigate waters full of obstructions a device called a leader gear recently was put in mee. iis consists of a cable laid on the bottom of a channel leading into a harbor or through a mine field. An alternating electric current is passed through the .cable and by means of delicate instruments placed aboard the ship it is possible. to obtain aural or visual indications of the cable. This enables the vessel to be steered safely, even at a speed Fe aircc in the war, efforts were Abstracted from a paper recently read before th North East Institution of alae and Shipbuilders, England, by Prof. J. C. McLennan, : of approximately 20 knots an_ hour. Wireless telegraphy and_ telephony made rapid developments during the war. By the use of oscillating ther- monic valves, the usefulness of these devices was greatly increased. It is now possible to hold communica- tion with ease between a land station and a ship or airplane over consid- erable distances. Exhaustive experiments have been carried out to obtain data regarding explosion pressures | for mine and depth charge operations.' When the effect of different charges at various distances is known, it can readily be determined how to lay out mine fields and what size and type of charges are the most efficient. In sound ranging investigations to determine the characteristics of pres- sure waves generated by the explo- sion of charges at sea, it was found that when a hydrophone was used 'to pick up the waves, a good record could be obtained by the explosion of a number 9 detonator at least two miles away. The explosion due to charges of two pounds of TNT have successfully been recorded at 14. miles. The explosion of 300- pound depth charges have been re- corded at 200 miles. f Based on these results, a system of sound ranging under water was devel- oped. Four hydrophones were laid out five miles apart along a base line in deep water, a mile or so from shore.. ~ tained and trained under In addition, two pilot hydrophones were placed along a line at right angles to the base line, one five, miles out and another ten miles out. Cables were laid from the hydro- phones to. a _ recording instrument placed in a shore station. With this sound ranging system, 'tthe shock of distant explosions occurring' under water affect the various hydrophones © in turn and as time intervals can be read to two or three thousandths of a second, it is possible accurately to measure the time intervals. By meas- uring the time intervals it is an easy matter to find where the ex- plosion that set up the sound wave took place. Up to 50. miles, the location of an explosion under water can be deter- mined within a few hundred yards by a single station but for greater accuracy the co-operation of two sta- 'tions are necessary to locate explo- sions at greater distances. Explo- sions of mines or torpedoes at any 466 ---Unique £ ailing Vessel--Bunkering Prices Throughout the World point in the North sea were readily located by stations in Great Britain. In the war, during the bombardment of the Belgian coast, it was common thing for a monitor to proceed in a fog to a position some miles from the coast and by dropping depth charges, have its position accurately determined from stations on_ the coast of England. So accurately was this done that it was found that when the monitor's guns were trained in selected directions, objectives sev- eral miles inland could be hit with regularity. To Train Seamen The United States Junior Naval Re- serve, which is sustained by the Amer- ican people for the training of boys for sea service, has received the hearty approval of many American shipping interests. This unit is not connected with the navy or supported by the government. Why shipping interests support the reserve, according to H. H. Raymond, president of the American steamship association, is as follows: -- "Tt is an axiom that.sea borne com- merce must have sea trained men. 'American crews for American ships' is not 4.mere slogan;: it: is a state- ment of a necessary correlative to our country's maritime position. American ships must have American crews, and such crews be men main- American standards and officered by American brains and discipline--with the im- gination, self-reliance, and Yankee ini- tiative that in the days of the clipper ship made our flag the wonder of the sea. Even before the war and prior to our country's great program of ship construction, American _ ship- Owners were painfully aware of their dependence upon alien labor. This well understood. weakness need not be di- lated upon here. A single instance is that on 453 American ships, of the lake and coastwise trade, the person- nel of American seamen was less than 14 per cent. "The United States shipping board has a well-planned and carefully ex- tended recruiting service and training system, which in connection with the like' effort of the navy department to help merchant marine needs has. ac- complished splendid results. But the training and opportunities offered under these plans have been neces-