LEARNING THE WATER'S SECRETS

Standing at this ear piece in the pilot-house, the captain can signal other boats, detect hidden dangers, and learn how far he is from a lee shore.

ered that, by immersing a microphone in a tank of water attached to a ship's side, they could hear the bell for a number of miles. But the sound was not at all like that of a bell rung in air, being more like the click produced by striking the backs of two knife blades together; and there were many other defects that kept the apparatus from meeting all needs.

Still, their apparatus was of such value as a substitute for fog horns and similar devices that it has been installed at some one hundred fifty points on shore throughout the world, and over twelve hundred ships have been equipped with it. The United States Navy regards this apparatus as indispensable on submarines. To its use is attributed the immunity of American submarines to accident-an immunity which is as unusual as it is fortunate, since in the two

years prior to the war, no fewer than five foreign submarines that did not have submarine signaling apparatus were lost.

Meanwhile, manufacturers set to work in the modern way to overcome the shortcomings of their apparatus; that is to say, they employed experts in various branches of science to attack the problem methodically until they found the solution. That is how Professor Fessenden came to work out his epoch-making device.

H. C. Berger, the Austrian physicist, made the first score. By attaching a piano wire to the hull of a vessel and vibrating it by a silk-covered wheel moistened with alcohol, he managed to send a clear musical note through water a distance of nearly two miles. But it was obvious that no wire could compress water sufficiently to set up the intense pressure waves that would carry over the distance required for a practical system of signaling.

Following up this clue, however, Professor Fessenden worked out an oscillator that would strike the wall of water with a force of two tons at the rate of a thousand blows a second. The sound waves thus generated produce a clear musical note instead of the dull click of the submarine bell, and this note carries for a good many miles. The sound can be broken into dots and dashes, and so be made to serve the purpose of a telegraph.

The Fessenden oscillator resembles, as much as anything else, a round box with a kettledrum inverted on the top. The interior of this kettledrum contains the essential parts. A ring magnet split in two parts surrounds the working parts. When this magnet is energized by an electric current, it produces a very strong magnetic flux. A central core with a double winding in opposite directions, through which an alternating current of five hundred alternations a second is directed, is mounted to lie along the axis of the ring. Lying in the space between the core and the magnet is a copper tube eight inches in diameter and eight inches long. The whole apparatus is twenty-one inches in diameter and fifteen inches thick, and weighs eight hundred fifty pounds; but its compactness makes it unnoticeable when in place.

The

tube oscillates with the current. movement ranges over only the hundredth part of an inch; but being repeated a thousand times a second, and striking blows of two tons at each stroke, which are communicated by means of a steel rod to a steel diaphragm an inch thick and two feet in diameter set in the hull of a vessel, it sets up vibrations in

the water that produce the sound for which inventors have sought so long. A telegraph key breaks the sound into dots and dashes; and by throwing a switch, the oscillator is transformed into a receiver, which, upon being connected with an ordinary telephone, allows the sounds made by other oscillators to be heard. Attaching a telephone transmitter enables the operator to speak through the oscillator as through an ordinary telephone for a distance of half a mile. Experiments on the revenue cutter Miami showed that the submerged parts of icebergs reflect the sound waves sent out by the oscillator, that the distance can be measured by noting the time required for the sound to travel to and from the iceberg, and that the direction is judged in the usual way.

When an alternating current is turned into the core, it upsets the even magnetic attraction of the ring, which has held the copper tube in place, and causes the tube to jump violently in one direction, as though it were going to shoot out from the circle of the core; and when the current is reversed, the tube jumps in the

Commander F. L. Sawyer has adapted the Fessenden oscillator for sending out signals to avoid collisions in fogs, by repeating automatically any given letter or combination of letters to indicate courses. By measuring the time between an instantaneous wireless and the submarine signal, the speed of an approaching vessel could be read. Knowing the course and speed of an approaching ship, the navigator would have no difficulty in

OHN SMITH, son of a farmer, is nineteen years old and four feet ten inches in height. His neighbor, James Brown, also the son of a farmer, is the same age, and six feet two inches in height. Both boys have been brought up under practically the same conditions, and yet one outstrips the other by a matter of sixteen inches.

Farmers Smith and Brown grow corn of the same variety on adjacent fields. Their seed actually came from a single lot. The one has plants whose stalks average ten feet in height and bear large full ears; the other has plants averaging six feet in height, with smaller and fewer ears. The natural conditions, such

as soil, moisture, and light, are the same. on both farms.

In one corner of Farmer Smith's field, right next to the big, tall stalks, is a little patch of pop corn. It was planted under the same conditions as the other corn, and receives the same attention. Yet both the stalks and ears are even smaller than the stunted plants in Farmer Brown's field.

What is the cause of these discrepancies? What factors have resulted in such a wide difference in a single, comparatively simple characteristic?

In order to answer these questions, some interesting experiments were conducted recently by Professor Albert F.

Blakeslee of the Department of Genetics, Connecticut Agricultural College. Material for his investigations was found in a company of 175 students at the college, ranging in height from four feet ten inches to six feet two inches, and in some specially prepared plots of corn in the Agricultural Botanic Garden of the college.

Of the 175 students at the Connecticut Agricultural College, the majority are between five feet six inches and five feet eight inches in height. Only one is shorter than five feet, and only one taller than six feet one inch.

Professor Blakeslee set out to discover whether heredity or environment had been chiefly instrumental in causing these

differences in height. Investigation of his pedigree disclosed that the small student came from a family, all the members of which were short, only one of them, a half uncle, being of average height (five feet eight inches), while all the other relatives of whom records could be obtained were under-sized, none of them being over five feet six inches. The tall student, on the other hand, was shown to have an entirely different an