MORE LIGHT!

Last Monday, February 11, Thomas Alva Edison celebrated his eighty-second birthday. The entire country heard his voice on that occasion over the radio. But when the scene shown on our cover took place, he was just approaching fame. A few of his inventions had been given to the world, others remained in the future. Then he was at work on the problem of producing an electric light for the home that would have none of the disadvantages of the arc light.

The story of the dramatic events at Menlo Park, N.J., on October 21, 1879, have often been told—how the bulb of the lamp was pumped for many hours to exhaust the air, how he had the glassblower seal off the bulb from the pump, how it was mounted on a wooden base, and the current started through it. A brilliant glow came. But would it last? Already other lamps had been made and had started off just as brilliantly, only to burn out too soon. Edison watched. The cover painting, made for the General Electric Company by H.H. Mott-Smith, shows this vigil, the "death watch" as his assistants called it. For hour after hour the lamp glowed, with Edison calmly and patiently sitting by. Forty hours elapsed before the lamp burned out. At last a successful lamp had been produced, and the electric lighting industry, which affects everyone so vitally, had been born.

NEW VALUE OF ELECTRON

Hailed by mathematical physicists as ranking in importance with the newly published Einstein paper, Dr. A.S. Eddington, Plumian Professor of Astronomy at Cambridge University, has just announced to the Royal Society here the results of research upon the charge of the electron.

Basing his work both on the theory of relativity and the quantum theory of light, Professor Eddington has found a formula that enables the charge of electricity in the electron, the electrical "atom" and building stone of which atoms are made, to be calculated from two other values. He proves that the value should be a whole number. As a result of these purely theoretical considerations, the famous Nobel prize experiment of Dr. R.A. Millikan, physicist of the California Institute of Technology, in determining this value may be proved to be slightly in error.

According to the most recent form of the quantum theory, which supposes that light travels as separate bursts of energy rather than as a continuous emission, the electrons are not tiny particles. They either consist of, or are associated, with waves in some peculiar manner. About this concept has grown the branch of physics known as "wave mechanics."

The two figures that Professor Eddington has used in computing the electric charge of the electron are the speed of light, which has been determined with extreme precision by Dr. A.A. Michelson of the University of Chicago, and what is known as Planck's quantum constant. The physicist represents it by the letter h. Light and other forms of radiation, like radio waves, differ in frequency, or the number of vibrations per second. The faster the vibration, the more energy there is in a single quantum, or "bunch," of the radiation. This energy is equal to the frequency multiplied by the quantum constant, which is named after Max Planck, the originator of the theory. The numerical value of h is 6.55.

"DECIBEL" LATEST UNIT

When telephone engineers get together in the future to talk about problems of transmission, the word "decibel" will figure largely in their conversation. That is the name that has just been adopted by the engineering staff of the Bell System to designate what has previously been known as the "transmission unit." It refers to the efficiency of telephone circuits. The new name was adopted after a conference between the representatives of the Bell System and the International Advisory Committee on Long Distance Telephony in Europe. The actual unit decided on was the "bel," named after Dr. Alexander Graham Bell, inventor of the telephone. The bel, however, is larger than is needed in practice, so the unit one-tenth as large, and therefore called the decibel, has been adopted by the engineers.

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