In the wide spectrum of electromagnetic wavesfrom the very short, very rapid cosmic rays (.000,000,000,004 cm.)* to the comparatively long, slow radio waves (2,500,000 cm.)only a small section is perceptible to unaided human senses. That section contains light rays and heat rays, and the intermediate infra-red rays which are neither light nor heat, yet are of the nature of both. Scientists are gradually learning how to put the infra-red rays to work. Doctors use them to create artificial fevers. Practical physicists used them otherwise last week.
In the auditorium of the Eastman Kodak Research...
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