Jim Webster devoted his professional career, both in the lab and in the field, to a broad study of halogens, sulfur, and other volatile species in igneous environments, which included plutonic, subvolcanic, and volcanic processes. As an experimental petrologist Jim contributed to our understanding of volatile processes in igneous melts and what minerals from these melts, such as apatite and micas, can tell us about these processes. In the field Jim focused on understanding the role of volatiles in volcanic systems and in plutonic systems, such as granites, in part through the study of apatite mineral chemistry and melt inclusions and how this related to the genesis and evolution of the original magmatic systems. In the case of volcanic systems this also included studies of outgassing during eruptions and subsurface volcanic processes.