JUNE 24.] THE NEW ZEALAND GAZETTE. 1669

the Hon. Minister of Finance of New Zealand for the purpose of establishing a public abattoir, the period of the said loan to be twenty-six years.

The common seal of the Mayor, Councillors, and Burgesses of Thames was affixed hereto by me, this 11th day of June, 1909.

FRANK H. CLAXTON, Mayor.

Thames, 11th June, 1909.

Notice to Mariners No. 43 of 1909.

Marine Department,
Wellington, 15th June, 1909.

THE following information, relating to submarine sound-signals which has been extracted from the June Pilot Chart of the North Pacific Ocean issued by the United States Hydrographic Office, is published for general information. In connection with this information it will be seen on reference to the New Zealand Shipping Gazette of the 27th February last that Captain L. W. Beavis in a letter to the manager of the Norfolk and North American Steamship Company, Limited, reports that without the aid of a microphone, by simply putting his ear to the side of the vessel in the forepeak, he heard the submarine bell of the Tongue Light-vessel on his port bow at a distance of six miles. By putting his ear close to each side of the ship he states that one can distinguish which side of the ship the sound comes from.

J. A. MILLAR,
Minister of Marine.

SUBMARINE SOUND-SIGNALS.

UNTIL recent times the sound-signals generally used to guide mariners, especially during fogs, were, with certain modifications, sirens, trumpets, steam whistles, bell boats, bell buoys, whistling buoys, rockets, gongs, bells struck by machinery, and cannons fired by powder or gun-cotton. In connection with all these implements the atmosphere is the medium of transmission of the sounds emitted from the sounding-apparatus; but it is a characteristic of the air that, in contiguous spaces of the atmosphere, the temperature, humidity, and pressure vary in such a manner as to produce a state which bears the same relation to sound as cloudiness does to light. Tyndall has thus described these conditions: "By streams of air differently heated, or saturated in different degrees with aqueous vapours, the atmosphere is rendered flocculent to sound. Acoustic clouds, in fact, are incessantly floating or flying through the air. They have nothing whatever to do with ordinary clouds, fogs, or haze; and the most transparent atmosphere may be filled with them, converting days of extraordinary optical transparency into days of equally extraordinary acoustic opacity."

The Inadequacy of Aerial Sound-signals.

The mariner has long since learned to be exceedingly cautious about depending upon aerial sound-signals, even when near. Experience has taught him that he should not assume that he is out of hearing distance of the position of the signal-station because he fails to hear its sound; that he should not assume that because he hears a fog-signal faintly he is at a great distance from it, nor that he is near because he hears the sound plainly; that he should not assume that he has reached a given point on his course because he hears the fog-signal at the same intensity that he did when formerly at that point, neither should he assume that he has not reached this point because he fails to hear the fog-signal as loudly as before, or because he does not hear it at all; and that he should not assume that the fog-signal has ceased sounding because he fails to hear it, even when within easy earshot.

While both the range and the certainty of the transmission of sounds through the air may be enhanced by imparting such excessive energy to the sound-waves as to render them less liable to the dissipating influences of a variable atmosphere, yet, with the fog-signals heretofore in use, it has been impossible to distinguish, by any means available to the mariner at sea, the times when he might expect aberrations in audition from the times when the sounds would be heard normally as to force and place.

The Superiority of Water as a Medium for the Transmission of Sounds at Sea.

Water is a less mobile medium than air, less responsive to marked variations of density arising through changes in temperature and pressure, and, therefore, less subject to variations of homogeneity and more reliable as an agency of the transmission of sound-waves.

Submarine Signal-bells.

In his experiments on Lake Geneva, in 1826, Colladon had a bell, weighing about 150lb., suspended some 5ft. under water from the side of a boat, and struck by a hammer attached to the end of a lever. Stationed in another boat, he listened for the bell-sounds propagated beneath the surface, which were conveyed from the water by a cylindrical tube of tin some 9 ft. long and 6 in. in diameter. One end of this tube terminated in an orifice for insertion in the ear, and the other was spread out somewhat in the form of a spoon, with its orifice closed by a flat elliptical plate of tin about 2 square feet in area. By attaching a suitable weight to the lower end of the tube it was easily retained in a vertical position with about four-fifths of its length submerged, its flat plate being turned toward the boat carrying the bell. With this simple apparatus Colladon was able to hear, with perfect distinctness, the blows of the hammer on the bell across the widest part of Lake Geneva, when the calculated distance between the two boats was not less than eight miles. The sounds which he heard appeared as if they had been caused by some metallic body striking the bottom of the tube, and they were as distinct at eight miles as at a few hundred feet from the bell. One set of observations was made during a strong wind. The waters of the lake, which were at first calm, became violently agitated, and it was necessary to keep the boat in position by means of several anchors, yet, notwithstanding the noise of the waves that struck the tube, he took observations with the same accuracy as when the air and water were still. And he states, "I am convinced that by employing a bigger bell, and improving or enlarging the hearing apparatus, easy communication could be effected under the water of a lake or of the sea up to fifteen or twenty leagues."

Plans for making a practical use of the water as a means of communication between vessels at sea commenced to germinate with the invention of the telephone in the latter part of the last century.

In his admirable work, entitled "The Modern Light-House Service," published as Senate Executive Document No. 56, Fifty-first Congress, first session, Mr. Arnold B. Johnson, Chief Clerk of the United States Lighthouse Board, has made reference to the experiments which were commenced in 1883 by Prof. Lucien Blake, whose plan he describes as follows: "A sound-producing apparatus was to be attached to each vessel, and to be worked under the surface of the water. In times of fog or at night a code of signals would be produced by it, which would be transmitted in all directions through the water with a velocity four or five times that in the air. Each vessel, in addition to the sound-producing apparatus, would be provided with sound-receiving apparatus, which would take up out of the water the signals arriving from the neighbouring vessels. For steamships the sound-producing apparatus was designed to be a steam fog-horn or whistle, especially constructed to sound under water and to be heard at least from six to eight miles.... As to the receiving apparatus with which each vessel was to be provided, the original plan of 1883, and which has not been changed, was to employ some form of telephone acting as a transmitter under water and connected with a receiver within the vessel....

It is along these general lines that the problem has been so successfully solved, under the auspices of the Submarine Signal Company of Boston, that the method of submarine sound-signalling has been officially recognised as supplying an important aid in navigation. As early as 1903, the United States Lighthouse Establishment had furnished the light-vessels at Boston, Nantucket, Fire Island, and Sandy Hook with submarine fog-bells. The equipment consisted of a bell with striking-mechanism actuated by compressed air, suspended at a depth of 30ft. or so beneath the surface of the sea from a davit at the side of the vessel; a small and compact air-compressor driven by a kerosene engine or by steam from the boilers of the light-vessel, for the purpose of furnishing power to operate the bell; and a code-ringer, also connected with the compressor engine, and adapted automatically to control the strokes of the bell so as to cause its ringing to send out the code number of the light-vessel.

The sound-waves going out from the light-vessels below the surface of the sea could be heard for a distance of some miles by passing ships equipped with microphones to receive submarine sound-signals. These sound-receivers are located inside of the hulls of ships below the water-line, and connected with the chart-room or bridge by a telephone circuit. On either side of the forehold there is fitted a small tank on the inside of the skin of the ship, without cutting the plating or making any alteration whatever in the hull of the vessel. A small opening in the top permits the introduction into the tank of a dense liquid in which the receiving microphones are suspended. By listening at the telephone, whose circuit includes both the port and starboard microphones, and switching the instrument from the starboard to the port microphone and back again, the tones of the light-vessel's