Abstract
From the rapid rise of the dispersion curve of rock-salt and sylvite in the ultra-violet, the existence of regions of anomalous dispersion in the Schumann region have been long anticipated. By using a specially constructed vacuum tube in connection with a vacuum spectrograph the regions of metallic reflection for NaCl and KCl were found. From these results an estimate was made of the wave-lengths of the true resonance frequencies. The values, 1547A for NaCl and 1581A for KCl, are in remarkable agreement with those previously calculated by Herzfeld and Wolf.

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