The early days of experimental neutrino physics.

The neutrino hypothesis, put forward by Pauli to account for the apparent loss of energy and momentum in beta decay, was verified by a series of measurements at a nuclear reactor nearly 25 years ago. An account is given of the first observations of the interaction of neutrinos in a target remote from the fission process that produced them. These experiments completed the observations of the particles involved in beta decay and paved the way for use of the free neutrino to probe the nature of the weak interaction.