The decrease of velocity of the β-particles on passing through matter

In a previous paper it was shown that the absorption of homogeneous β-rays by matter when determined by the ionisation method does not take place according to an exponential law, as had previously been assumed, but according to a law which is practically linear. This means that the absorption coefficient of the rays becomes greater the further the rays penetrate the absorbing medium, and since the absorption coefficient increases with decreasing velocity of the β-rays it suggests that the rays are slowed down on passing through matter.