THE three-electrode valve offers a very simple and trustworthy method of amplifying the small currents produced in the thermopile of an infra-red spectrometer. Bright lines are more readily picked up ...
IN a communication, dated October 17, from the Smithsonian Institution, Washington, an account is given of experiments made by Dr. Charles G. Abbot, secretary of the Institution and Mr. W. H. Hoover, ...
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