-RAYS
When the ionization is due to the passage of
-rays through matter, the evidence of the oil-drop experiments as well as that of C. T. R. Wilson’s experiments (see [chap. IX]) on the photographing of the tracks of the
-rays is that here, too, the act consists in the detachment of one single electron from a single atom. This experimental result is easy to understand in the case of the
-rays, when it is remembered that Wilson’s photographs prove directly the fact, long known from other types of evidence, that a