"When I began life as a particle physicist fifty years ago, most of the major discoveries were made in Europe by people studying the cosmic rays that bombard the earth from outer space. Particle physics was done by observing the debris produced by cosmic rays as they pass through the atmosphere and the experimental apparatus. The debris consists of particles with short lifetimes and unfamiliar names. ... Three young Italians, Conversi, Pancini, and Piccioni, working with home-made particle counters in the chaos of postwar Italy, discovered that the common cosmic ray particle, later called the muon, had only weak interactions with matter. Cecil Powell, working with microscopes and photographic plates at Bristol in England, discovered the strongly interacting cosmic ray particle, which he called the pion. Other strange new particles were discovered by Rochester and Butler using old-fashioned cosmic ray cloud-chambers in Manchester."