loud that it was not necessary to talk directly into the former or hold the latter to the ear, though a switch is provided for using a receiver as in an ordinary telephone whenever it is desired to keep communication secret. After pressing a call button the user of the dictograph can lean back in his chair, turn his back to the instrument or get up and walk around the room, dictating all the time to a stenographer in a distant room or carrying on a conversation with a party a block or a mile distant. Its use has by no means been confined to dictation, for it has proved to be a handy means of intercommunication in offices, factories and elsewhere.

The dictograph is uncannily acute. One may stand eight feet away from it and whisper, yet the words will be distinctly heard by the listener at the other end of the wire. Nor can it be muffled. I

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pressed a folded coat against the transmitter, leaned against the coat, then talked in an ordinary tone to a party in a distant room on another floor upon unexpected subjects. Even that did not fool the dictagraph, for the answers returned showed that every word was understood.

After all these various uses of the dictograph had been developed and not until then, was a special form of apparatus devised for detective work. The complete outfit is so small that it can be slipped into a coat pocket without making a bulk that would attract attention. The sound collector is a disk of hard rubber three inches in diameter which may be concealed behind the wall paper, beneath a rug, in the furniture, back of a picture or anywhere else. So long as the parties to a conversation do not wander too far from it every word they utter may be heard by a distant listener. Whispering

is of no avail. sounds become distinct. The first impression of the dictograph is amazement that an instrument so exceedingly sensitive could be made. But after all the dictograph is not so wonderful as the fact that it should have remained so long unutilized. Away back in 1878, when the inventor of the acousticon was nineteen years old, D. E. Hughes, an Englishman who became a professor in the college at Bardstown, Ky., the inventor of the printing telegraph that bears his name, produced an ancestor of the acousticon so sensitive that it actually rendered audible the footfalls of a fly!

This was two years after Alexander Graham Bell had astonished the world by exhibiting the first

telephone at the

Centennial Expo

peratures, that of carbon decreases. These qualities seemed to render carbon the ideal substance for further experiments; so Professor Hughes sharpened both ends of a pencil of carbon, then placed the points in depressions in blocks of carbon fastened to a wooden sounding board mounted on an insulated base and connected with a battery cell, and a telephone. With this crude apparatus he was enabled to hear flies walking and many other sounds never before audible. Because this apparatus did for the sense of hearing what the microscope does for vision Professor Hughes called his invention the "microphone." In an article. published in the English Mechanic June 21, 1878, the suggestion was made that in time of war the microphone

Scientists everywhere were deeply interested

in the marvelous instrument and a great many of them were trying to supply the improvements it so sadly needed. In the course of his experiments Professor Hughes attached a tenpenny nail to each of the two wires leading from a receiver, then placing the two nails side by side laid a third nail across the first two. The loose metallic contact thus provided so improved the sound conducting properties of the crude telephone that Hughes began a systematic development of his discovery.

Carbon being unoxidizable and unalterable in air, may be relied upon to produce unvarying results. It also possesses to a marked degree the power of absorbing and condensing the air in its substance. While the resistance of metals to an electric current increases with higher tem

the approach of an enemy when several miles distant, and that it might even determine whether infantry, cavalry or artillery was marching. Many other strange uses were suggested for the instrument, including the detection of subterranean noises which generally precede volcanic eruptions and earthquakes. As a matter of fact the dictograph actually was used by Prof. Frank Perret, of Boston, on Mount Vesuvius in predicting the earthquake that destroyed Messina a couple of years ago.

In due time Hutchison, who has a long list of inventions to his credit, one of which you probably will hear the next time you fail to step lively in getting out of the way of an automobile, became chief engineer for, and personal representative of, Thomas A. Edison. In fact Edison narrowly escaped inventing the

San Pedro, California, and perhaps with the idea that a taste of life ashore would be pleasant for a change, he hunted a job. The water company had a position waiting for this A. B., a steady job for a man who was willing to stay with it, and the ex-sailor went to work cleaning the company's ditches.

This was the beginning of William Mulholland's connection with the water supply of Los Angeles; he has stayed at this work ever since, but the difference is that he is now chief engineer of the "$23,000,000 ditch," the Los Angeles aqueduct, which has been under construction since 1908 and is expected to deliver water in 1913. It will be about 250

miles long.

The work has gone through smoothly in spite of the enormous obstacles, natural difficulties, financial stress and political opposition, for being a municipal

undertaking, the project has been subject to attack by every selfish office-seeker.

William Mulholland was born in Belfast, Ireland, in 1855, received his schooling in Dublin, followed the sea from 1870 to 1875 and after entering the Los Angeles Water Company's employ made a thorough study of hydraulic engineering. When the plant was bought by the city in 1902 he was appointed superin

tendent and chief engineer, and he was one of the principal factors in promoting and executing the great aqueduct project.

For a man at the head of a gigantic enterprise, Mr. Mulholland's manner is remarkably unassuming. His rugged features reveal the quiet strength of the man, and physically, too, he suggests strength; not a tall figure, but a sturdy, well-knit frame. His thoughtful eyes and well developed head indicate the men

tal vigor of a man who could work his way to the top of an engineering project requiring the highest technical skill, a man who was a day laborer and was forced to seek his own education.

It has been a favorite teaching of some educators of late that a college course alone could equip a man today for the most highly-skilled professions. The success of the Irish sailor refutes this. Somehow or other he has acquired the necessary technical knowl

edge to put through this gigantic undertaking.