This is the third edition of an important reference work—or at least that is the official count. In reality, for those of us who remember the original 1957 edition and the 1960 “revision,” this is the fourth. Aside from quibbling, however, it is useful to recall the origins of this work. Additionally, it is nostalgic for me, since in those days I was beginning my education as a geologist, and the presence of the “Glossary” was a source of comfort and amusement at the