An effort is made to distinguish more clearly between two types of phenomena which may occur in some glasses: (1) a ``reversible absorption'' current due to the formation of a high counter electromotive force, and (2) an ``irreversible absorption'' current due to the formation of a highly resistant layer in the glass. Characteristic curves showing one type of the latter which may occur under certain conditions are given. Although many observers seem to have observed both phenomena previously, considerable confusion still seems to exist in distinguishing between them. Combinations of both phenomena may be one possible cause of some of the large discrepancies in current‐time behaviors reported. A study of the relatively small, slowly decreasing residual electromotive force observed upon discharging the sample shows a linear increase of this electromotive force with increase in temperature for temperatures as high as 150°C.