Nikola Tesla, 75 Today, Working on Mysterious Source For Electricity

One of World's Greatest Inventors Refuses to Reveal Experiment Until He Proves Calculations; Honored on Birthday

New York, July 10 — (AP) — Nikola Tesla, one of the greatest electrical inventors since Benjamin Franklin flew his historic kite, was 75 years old today.

He was presented with a volume containing letters of felicitation and congratulation from about 100 inventors and scientists all over the world.

Tesla has left behind him three quarters of a century of high achievement, being generally considered the father both of radio and of modern power generation and transmission, but it is in the fourth quarter he expects to do his greatest work.

Born In Serbia.

Among the authors of the congratulatory letters presented the inventor today were such men as:

Sir Oliver Lodge, E. F. W. Alexanderson, Lee De Forest, John Hays Hammond jr., Robert A. Millikan, Secretary of Commerce R. P. Lamont, H. H. Westinghouse, B. A. Behrend and Count Van Arco.

Tesla was born in Serbia, coming here as a young man and obtaining his first job in America with Thomas A. Edison. Soon, however, he founded his own company and in 1888 he sold to Westinghouse a series of patents which revolutionized the electrical industry.

Since then he has always worked independently, delving deep into the mysteries of the earth's energy and delivering his findings to the peoples of the earth. He early became an authority on power and played a large part in the harnessing of Niagara Falls and many other large power projects. Later he turned his attention to wireless and on his research is based much of the developed art now known as radio.

A tall, thin man with angular features and graying hair who carries his years as lightly as most men of 50, he is working on power again now, power of great strengtlı from some source he is not yet ready to divulge. He is nearing the end of a road he has been traveling for more than a quarter of a century and he expects his labor to bear fruit which will be his greatest triumph.

"I am naturally anxious to give the facts to the world as soon as possible," he said, 'but I also wish to present them in a finished form. That may take a few months, or a few years."

Sure of Untapped Supply.

So far, he said, he has proved his theories concerning the hitherto untapped source of immense power by experiments and he was confident that calculations based on these experiments would prove true.

"If so," he continued, "then a new source of power, available at every point of the globe, in amounts practically unlimited, will be opened up."

Tesla looks on his latest work as a lasting monument which will carry his name proudly down the ages after he is gone.

"I have been wonderfully fortunate," he says, "in the evolution of new ideas, and the thought that a number of them will be remembered by posterity makes me happy indeed. I am confident that my rotating field and induction motor and the wireless system I have given to the world will live long after I have gone. Nevertheless it seems to me my latest discoveries will be considered the most important."