As his strength returned there came back with it the old determination to make a wireless set that would work. He got out of bed and went back to the shop. And there he continued the experiments which were destined to result in one of the most important inventions of the past fifty years.

That incident is typical of the life of Lee De Forest, the inventor of the wonderful "audion" vacuum tube which has made radio, as it is today, possible. Talking with him in his big studio-laboratory in New York, it was hard for me to realize that only a few years ago he was engaged in a never-ceasing struggle and meeting only with defeat. During the early part of his career, under the handicaps of poverty and unbelief, he worked out his ideas to a successful conclusion, using each failure as a stepping stone. Later, when he had perfected his invention, he had to fight just as hard to make people believe in it.

Now, twenty-three years after he started the experiments that led to the discovery of the audion vacuum tube, most of the radio receiving sets in the United States and the number of them is estimated at more than three million are operated with these tubes. They have made broadcasting possible.

Every radio fan knows what a vital part of his set the vacuum tube is. But not everyone knows that these tubes are used in dozens of other ways. By

means of them sound can be amplified, or magnified. A whisper can be changed to a roar.

Transcontinental wire telephony was made possible by means of this tube. With the aid of the induction coil invented by Professor Michael Pupin, of Columbia, the human voice would carry by telephone for several hundred miles, but not the three thousand miles from New York to San Francisco! It was only by using the DeForest amplifiers that the first coastto-coast telephone conversation was held, in January, 1915.

By means of these tubes President Harding's voice was magnified more than a million times when he made his inaugural address to an audience of a hundred thousand persons; yet he did not have to speak above an ordinary tone.

The tubes aid hearing by the deaf, they amplify the sound of the heart for surgeons, and when used with the radio compass, they help ships to find their way through the fog. By means of the tubes a ship can follow a charged wire down a winding channel which has no buoys or markers. In addition to all these things, the tubes will generate power.

De Forest was born in 1873, in Council Bluffs, Iowa, where his father was a Congregational minister. Like most ministers, he had no income except his small salary. When De Forest was six years old the family

moved to Muscatine, Iowa; where he first went to school. In the early eighties his father was sent to Talladega, Alabama, to take charge of a mission school for educating the negroes.

He had always hoped that his son would follow him in the ministry, but De Forest wanted to be a mechanical engineer. Up to this time he had given no indication of being an electrical genius; but he began to show indications of his enormous capability for study. Night after night his father had to drag the boy from his books and send him to bed.

In 1891, when he was eighteen years old, he made up his mind to go to a preparatory school to fit himself for the school of mechanical engineering at Yale. His father had no funds with which to finance his education, so the boy had to earn his own way. He did this by working as a book agent.

In the fall of 1893 he entered Yale for the threeyear course in mechanical engineering, was graduated in 1896, and stayed three years more for post-graduate work, leaving Yale in 1899 with the degree of Doctor of Philosophy. During all that time he had paid his way by mowing lawns, waiting on tables, and taking care of furnaces. One summer he worked as a waiter in a hotel on Block Island.

His father died in 1896, leaving an estate barely sufficient for the needs of his mother; and after De

Forest's graduation, in 1899, he went to Chicago and got a job testing and assembling dynamos for the Western Electric Company, at eight dollars a week.

It is hard now to realize that less than twenty-five years ago radio was just beginning. Marconi had succeeded in receiving wireless signals with only fair reliability by using his "coherer.” This was a tube full of silver filings. When a wireless wave struck it, the filings were attracted to one another and clung closer together, and a current of electricity could be passed through them.

While he was at Yale, De Forest had become interested in wireless and believed that he would work out a better detector than the one Marconi then had. In Chicago he paid two dollars a week for a room, which he shared with two other men; his meals cost only from fifteen to twenty-five cents each, and the little he could save out of his eight-dollar salary went on materials for experimenting. He spent his evenings in his room under the gaslight, filing, tapping, and testing his detector.

Late one night, in the fall of 1900, he had put his table directly under the gaslight so that he could see better. The gas jet was fitted with a Welsbach mantle burner. Over in a closet, eight feet from the table, he had a spark coil. By pulling a string he could

turn the coil on and off. The coil generated waves, for which he listened in his detector on the table.

He was bothered, however, by periodical dimmings of the gaslight. And after a while he noticed that whenever the spark coil was working the gaslight grew dim. This interested him so much that he temporarily abandoned his experiment in order to observe the curious behavior of the gaslight. Again and again he pulled the string attached to the coil; and every time the spark coil buzzed, the light grew dim! When the coil stopped, the light blazed up again.

For several days, during every minute of his spare time, he studied the phenomenon of the gaslight which responded to radio waves, trying to discover why it dimmed and brightened. Then he stumbled on a disheartening fact: When the closet door was closed the light no longer responded. Experimenting further he found that the gas flame was responding to the sound of the coil, and not to its electrical waves.

Philosophically, De Forest swallowed his disappointment, and went back to his original experimenting. For the time being, he tried to drop the idea in regard to the gas light, but it stuck in his mind. While he worked on his detector, it recurred to him again and again. He had a "hunch" that heated gas might offer a better solution of the problem of wireless