DISPLACEMENT

NEW TYPE OF SUBMARINE 340 FEET IN LENGTH DOING 24 KNOTS UNDER STEAM. NOTE THE THREE 4-INCH GUNS, TWO FORWARD AND ONE AFT; ALSO THE TWO SMOKESTACKS, WHICH FOLD DOWN WHEN THE SUBMARINE SUBMERGES. SUBMERGED 2700 TONS, SPEED 10 KNOTS.

AUSTRO-HUNGARY'S DIMINISHED MERCHANT FLEET.-At the outbreak of the war Austria possessed 186 ocean-going ships, aggregating 757,043 gross tons. In addition, there were under the Austrian flag 25 vessels employed in short sea trips and 163 miscellaneous craft engaged in the coastwise trade, making a total of 374 vessels with an aggregate tonnage of 812,343 gross tons.

Of the just enumerated merchant tonnage 156,113 tons was captured, 113,053 tons sold to foreign owners, and 46,164 tons sunk by enemy action during the course of the war. The aggregate loss amounted to 315,330 tons. New ocean-going tonnage constructed in the same period amounted to 63,344 tons. When hostilities closed, therefore, Austria's merchant fleet had diminished to 296 ships of a gross tonnage of 560,357 tons.

In the case of Hungary the country had on August 1, 1914, only 69 ocean-going ships of 211,621 gross tons, 42 short sea-going vessels of 3690 tons and 62 coasting craft of 18,411 tons, or a total of 173 ships of 233,722 tons. While hostilities lasted ocean-going vessels of 51,391 gross tons were captured and vessels of 7049 tons sunk through enemy action. Seven ocean-going ships of 25,289 tons were sold to foreigners. From this total tonnage of 83,729 tons lost, there should be deducted 6152 new tonnage constructed. At the date of the signing of the armistice Hungary's merchant fleet consisted of only 109 ships of 156,145 tons.-Nautical Gazette, 8/3.

FRANCE

FRENCH DESTROYER DAMAGED.-Paris, Jan. 7.-The French destroyer Enseigne Henry was damaged in the Black Sea on the morning of January I as the result of a mine explosion. She was able to reach Constantinople under her own steam. Four seamen were killed by the explosion.— London Times, 8/1.

FRENCH NAVAL LOSSES IN THE WAR.-A full list of the French naval losses in the war, which has been published, includes four battleships, the Bouvet, Suffren, Gaulois and Danton; four armed cruisers, the Leon Gambetta, Amiral Charner, Cleber and Dupetit Thouars, and one fast cruiser, the Chateau Renault. There were, besides, fourteen destroyers, eight torpedo boats and fourteen submarines lost. One of the submarines, the Duric, was refloated by the enemy, but was subsequently recovered. The minor ships which were sunk were five auxiliary cruisers, four gunboats, 72 submarine chasers, one sloop and seven small craft.

The loss in tonnage was 110,000 tons, against 550,000 tons for England, 76,000 tons for Italy, and 17,500 tons for the United States.-Nautical Gazette.

WALSER'S HYDROPHONE. The fundamental fact upon which Lieutenant Walser built is that sound, like light, is refracted on passing from one medium into another. We are accustomed to diagrams which assume that the complex of light from a given object consists of a number of component waves, which may be taken to be parallel if their source is sufficiently remote, which remain parallel so long as no obstruction is interposed in their path, and which are bent as soon as they are called upon to enter a medium of different density from that in which they were propagated. And it is just so with sound waves.

Walser therefore interposed, in the path of sound waves, a sort of acoustic lens. Just as in the case of light, this causes the individual waves which make up the sound complex from a given source to come to a focus, with the double effect of strengthening them and isolating them from the sounds that proceed from other sources. In fact, the several sources of sound give rise to as many foci, of which the geometric locus can be determined by calculation; and in the same way, from the position of the sound focus which pertains to any particular source of sound, the position or at least the direction-of that source can be calculated.

Once this general idea had been formulated, it remained for the lieutenant to work out the practical details. As finally adopted and used with huge success in the detection of submarines, the acoustic lens was in the form of a spherical segment A, set into the side of the chaser or destroyer. In the bulging surface of this are a series of circular holes B. each filled with a sensitive vibrating plate C. The effect is to focus all sounds received; and the focal points all lie on a circle I, whose position, of course, depends upon the radius of the lens segment and other factors which can be controlled. There are two of these lenses on each vessel, one to port and one to starboard. The two give upon a single cabin, which of course extends the entire width of the ship, and is well insulated against sounds at all points save the two lenses. The observer is seated in the center of the cabin, with a listening helmet to which are attached two eartrumpets, of which only one is shown at D in our diagram. One trumpet, of course, pertains to the port lens and one to the starboard.

The trumpet D is carried on a fork E, which is moved from the wheel H through the arm F and pivot G. The wheel H is connected with the rotating drum that appears in the general view; and the mechanism is so adjusted that as the operator turns the handle of this drum, the two trumpets revolve about the respective focal circles of the sounds received. The counterweight J and cord K hold the trumpet in a position where its axis is constantly directed toward the center of the spherical lens. The counterweight L maintains the equilibrium of the mobile arm F. The counterweights M, M', cause this arm to oscillate about the pivots N, N', in such manner as to counterbalance the effect of the ship's pitching and keep the mouth of the trumpet always in the same horizontal plane. The entire apparatus is supported by the frame O.

In using the apparatus, the observer can hear a given sound, not only when the trumpet is precisely centered at the focal point of that sound, but when it is anywhere in the neighborhood of that point. He hears it loudest and clearest, however, when the axis of the trumpet passes through the focus, so that the trumpet is centered about the focus. He explores the field by keeping the trumpet continually in motion; and he locates every suspicious sound by carefully bringing the trumpet to the position where it is loudest and clearest. The instrument has been previously calibrated, so that when he succeeds in getting the maximum intensity for a given sound, he reads the direction of its origin on the scale that runs

about the edge of the drum. The distance is then estimated roughly by taking account of the intensity of the sound at its maximum; and it is then easy to steer a straight course for the source-and, if the latter be a submarine, to pass directly over it with mathematical accuracy and drop sudden death upon it.

The first successful experiments with a more or less definite model were made on March 31, 1917. After that, progress was slow, both in the way of removing the last technical obstacles, and in the more difficult business of convincing the "appropriate authorities" that here was something good. All these difficulties were surmounted, however; the apparatus was installed, and on March 16, 1918, it received its baptism of fire. Its success was immediate; and from that date to the end of the war it made a very large contribution to the nullification of the submarine menace.Scientific American, 8/3.