Light & Sight

Guarded deeply in a Paris cellar is a long platinum bar. When its temperature is that of melting ice (0DEG Centigrade, 32DEG Fahrenheit) two marks on that bar are exactly one metre apart. That Paris metre is the modulus of the world's weights and measures.* If the standard bar were lost, and all its master duplicates in the capitals of civilized countries, scientists would be hard put to recalculate the metre distance, except. . . .

That exception is the fact that Professor Albert Abraham Michelson of the University of Chicago has very accurately calculated the speed of light. It travels 186,000 miles a second. That figure, Professor Michelson said at Washington last week, was not more than one mile from exactness. And now scientists knowing that, he proudly repeated, can at any time they please remake the Paris standard metre.

Professor Michelson's presence at Washington last week was a joy to him. The Optical Society of America was meeting there, in the auditorium of the Bureau of Standards. Several hundred physicists who have been searching out light's properties and effects hailed him as one of their greatest. He had measured light data upon which Albert Einstein was able to base his relativity theory.

Silence came upon the auditorium crowd. Dr. Herbert Eugene Ives, physicist for the Bell Telephone Laboratories and one of the inventors of television, nervously approached Professor Michelson and in a timid-seeming voice presented him with the Optical Society's Frederick Ives Medal. Dr. Ives gave the Society money for the biennial presentation of the medal in memory of his father, the late Frederick Eugene Ives, inventor of photoengraving.

The presentation done, Dr. Ives explained to the physicists present a new camera invented by Dr. Clarence Whitney Kanolt of the U. S. Bureau of Mines. It makes pictures seem lifelike. In front of the photographic plate is a glass grating of alternate vertical light and dark lines. In photographing, the camera so moves before the subject that its centre is always on a line with the centre of the camera lens and plate. The finished picture is striped. Some of the stripes show the person or thing from one angle, others from other angles. When a second glass grating is placed over the picture it makes the proper groups of stripes seem a solid photograph. The pictures are called parallax panoramograms.

Another interesting machine described at the meeting was the recording spectrophotometer devised by Professor Arthur Cobb Hardy of Massachusetts Institute of Technology and General Electric's research staff. In the machine is a glass prism which breaks up the light reflected from any colored object into its spectroscopic lines. A chart of those lines is photographed and the picture may be sent by wire or wireless anywhere. Useful can this device be for recording the exact tints of textiles, oils, soap, cheese, lard, flour, butter, chocolate, glass, automobiles, tile, brick, roofing material, carpets, rope, hardware, paper, leather, cement, linoleum, cosmetics.

Still another significant invention came before the Optical Society. It was a refinement of Dr. William David Coolidge's cascading cathode tube which shoots pure electrons out through a thin nickel window (TIME, Nov. 1, 1926). The new tube's window is made of pyrex glass thinner than tissue paper and permits more electrons to escape from the tube's cathode than does Dr. Coolidge's nickel window. And the new contraption is relatively cheap, available for research laboratories everywhere to experiment with the mightiest rays that man has yet learned to control. Remarkable is the fact that Dr. C. M. Slack, Westinghouse Electric's inventor of the glass window, is only 27.

Obliquely interesting to the light physicists at Washington was the California Institute of Technology's decision to build a 200-inch telescope near Mount Wilson. The present Mount Wilson apparatus has a 100-inch reflecting mirror. The new one, to be done in three years, will double the astronomer's vision, quadruple the amount of light that at present can be caught from the stars. The great mirror, about 17 feet in diameter, is possible because Professor Elihu Thomson of the General Electric Co. has learned how to fuse quartz into great discs that will not crack, nor warp with heat.

(Professor Einstein, frantic with the imminence of death from heart trouble, has been intensely working on two new theories corollary to relativity. One he has just submitted to the Berlin Academy of Science, for study. The other is yet unfinished. Last summer he spent at Lubeck, Baltic sea resort. Last week he was in Berlin, reasoning a few hours each day in a small, secluded room atop his apartment house. His malady has made him annoyingly nervous and querulous. In his wife's words, if someone suddenly disturbs him, he screams, shrieks and raves. Then he calms down and talks. Violin playing is his sedative, his solace.)

*It equals 39.37 U. S. inches, 39.370113 British inches.