The curve exhibits the same peculiarities as those given by Bragg for a thin film of matter of one kind. The ionization of the α particle per unit path increases slowly for about 4 cms. There is then a more rapid increase just before the α particle ceases to ionize the gas, and then a rapid falling off. The ionization does not appear to end so abruptly as is really the case, since there is a correction to be applied for the angle subtended by the cone of rays. The maximum range of the α rays in air was 6·7 cms., a number in agreement with that obtained by Bragg by measurements on the range of the rays from radium.