While the chemical aspects of igneous petrology have dominated research for many years, the physical processes associated with the generation, transport, and crystallization of magma have been somewhat neglected. Here a group of distinguished scientists, whose current research embraces both chemical and physical aspects of the field, illustrates these new directions in igneous petrology. Originally published in 1980. The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These editions preserve the original texts of these important books while presenting them in durable paperback and hardcover editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.