The deep-seated conditions to which the present surface rocks of the pre-Cambrian area in northern New York were subjected when the tremendous molten masses were intruded into the thick Grenville sediments were decidedly favorable for both magmatic differentiation and assimilation. Probably few regions present any better opportunities for the study of such phenomena. It is the purpose of this paper to bring together published and unpublished observations bearing on these problems and to present certain conclusions which have an important bearing not only on Adirondack geology, but also on the broader problems of petrology.
Particular acknowledgments are due Professors Cushing, Kemp, and Smyth, all of whose publications pertaining to the geology of the region are so familiar to the writer. During the past eight years the writer’s work has been largely confined to the southern half of the Adirondack region and has resulted in the detailed mapping of about . . .