How did Ernest Rutherford distinguish alpha radiation from beta radiation?

Ernest Rutherford distinguished between alpha and beta radiation by observing their varying abilities to penetrate matter. By placing uranium near thin foils, he discovered that the radiation was more complex than previously assumed: one type was easily absorbed or blocked by a very thin foil, while another type often penetrated the same material.

For the sake of simplicity, he named these two types alpha and beta, respectively. It was later determined that alpha particles are identical to the nucleus of a helium atom, while beta particles are equivalent to electrons or their positive counterparts, positrons.1