In the higher parts of the Sierra Nevada the dominant rock is granite. By reason of Pleistocene glaciation the exposures are exceptionally fine. Over broad areas glacial erosion has removed the products of decay, laying bare the unaltered rock, and large portions of these areas are free from glacial débris. On most of the drift-free surfaces postglacial decay has made little progress and vegetation has as yet no foothold. In many places one can walk for miles on firm granite, and tracts of ideally perfect exposure are often many acres in extent. Taking account of the further fact that the summer climate is usually dry, I regard the region as one of the finest in the world for the study of problems associated with large bodies of granite.
My acquaintance with the Sierra granites is superficial and fragmentary. While engaged in physiographic and glacial studies I have traversed them . . .