The hypotheses of the formation of granite by consolidation of magma derived from depth and of granite formed by granitization in association with magma intrusion are accepted as valid concepts. The results of a study of over 2000 square miles of the northwest Adirondack Highlands pre-Cambrian igneous complex are presented, and the two concepts are found far more appropriate to explain the source of the introduced material of the widespread granite masses occurring there than recourse to the hypothesis of “emanations” (hydrothermal solutions, gases, or migrating atoms and ions) from depth. It is concluded that over 85 per cent of the northwest Adirondack granitic rocks are the product of consolidation and differentiation of magma intruded as sheets or phacoliths and that less than 15 per cent is the product of migmatization and granitization of metasediments and amphibolite.