ABSTRACT
The method depends on the linear magnification of the ionisation current, due to a few millimetres of the track of an α-particle, by means of valves and the recording of the momentary current on a photographic film by a special oscillograph. It suffices to say that about 17 million of the α-particles from radium C have a range of about 9 cm. Any protons near the end of their range would give a record similar to a swift α-particle, while the disturbance due to the α-rays emitted from the source makes it difficult to count α- particles near the end of their range when the ionisation is small. An analysis of the distribution of the long range α-particles from radium C of ranges between 7 cm. It is concluded that at least nine homogeneous groups of α- particles are present for which the ranges and numbers have been measured.
