Tammy Welch, age 13, of Vancouver, Wash., for her question:

WAS THOMAS EDISON REALLY DEAF?

Thomas Alva Edison was probably the greatest inventor in history. Although he had only three months of formal schooling, his inventions changed the lives of millions of people.

Edison definitely had a hearing problem. During his last years he could barely hear a shout. An operation could have cured his deafness, but he refused to undergo surgery. The great inventor said that he didn't mind being deaf because he found it easier to concentrate.

At the age of 12 Edison sold newspapers, candy, sandwiches and peanuts on a train that ran between Port Huron and Detroit in Michigan. In his spare time, he experimented with chemicals in the baggage car.

One day a stick of his phosphorus burst into flame and set the baggage on fire. The conductor boxed his ears and threw him off the train. The conductors' blows may have caused Edison's later deafness.

But Edison himself though the deafness was the result of a later accident. A well meaning conductor caught hold of Edison's ears to pull him up to the platform as the train was pulling out of a station. "I felt something snap inside my head," Edison reported later. "My deafness started from that time and has progressed ever since."

Edison was born in 1847 and lived to be 84 years old. During his lifetime he had 1,093 inventions patented. He defined genius as one percent inspiration and 99 percent perspiration. And he demonstrated this belief by working for days at a time, stopping only for short naps.

One of Edison's greatest inventions was the electric incandescent light. His favorite invention, perfect in 1877, was the phonograph.

Edison also receives credit for inventing one of the first successful motion picture devices and he also contributed to the development of sound movies.

Edison also improved the telephone by adding the carbon transmitter.

Edison patented improvements on the stock ticker that netted him his first large sum of money. In 1869 he sold his patents for the sum of $40,000.

The inventor said that often he tried everything while working on his inventions. He generally ignored scientific theory and mathematical study that might have saved him time. But failure never discouraged him.

Once, when about 10,000 experiments with a storage battery failed to produce results, a friend tried to console him. "Why, I haven't failed," Edison said. "I've just found 10,000 ways that won't work."

One of Edison's well received inventions was his development of a stencil duplicating process that was used in the first Mimeograph machine produced by the A.B. Dick Company in 1887. The machine made copies by forcing ink through holes in the stencil.

Edison's first invention was a vote recorder. His last was a method of making synthetic rubber from goldenrod plants.