Perhaps the most controversiaZ aspect of this voZume is the number (V) assigned to the conference in this series. ActuaZZy, the first conference to be heZd under the titZe '~tomic CoZZisions in SoZids" was heZd at Sussex University in EngZand in 1969 and the second at GausdaZ, Norway in 1971, which wouZd ZogicaZZy make the conference heZd at GatZinburg, Tennessee, U.S.A. in 1973 the third (III). However, the appearance of the proceedings of the 1971 GausdaZ Conference (pubZished by Gordon and Breach) bore the number IV. The reasoning behind this was that, in fact, two pre vious conferences had been ZargeZy dedicated to the same subject area. The first of these Was at Aarhus, Denmark in 1965 and the second in 1967 was heZd in ChaZk River, Canada. Hence, the number V for the 1973 meeting. ActuaZZy, the conference can easiZy be traced back to Paris, France in 196Z when it went under the coZorfuZ titZe of '~e Bom bardement Ionique." In 1962 a smaZZ conference was heZd at Oak Ridge, Tennessee, U.S.A. at which the discovery of channeZing was first formaZZy annunciated. This was foZZowed by conferences at ChaZk River, Canada in 1963 and at HarweZZ, EngZand in 1964. More over, immediateZy foZZowing the ChaZk RiVer conference in 1967 there was a conference on higher energy coZZisions at Brookhaven, New York, U.S.A. Thus, strictly speaking, the Gatlinburg meeting is the tenth (X) in the series.