Selenium Cell

A selenium resistance box. Vitreous selenium is made by keeping ordinary selenium for some hours at a temperature of about 220º C.(428º F.) after fusing. It is placed in an electric circuit as part of the conductor.

Its resistance can then be determined. It decreases in sunlight to about one-half its resistance in the dark.

The selenium cell is used in the Photophone, q. v. Otherwise it is little more than a subject of experiment.