INTRODUCTION	25
	pressly said so, to obliterate the " metamorphic and metasoma-tic schools." By it he assumed a mineral " protoplasmic mass " which, as the result of crystallization and cooling, " had already become porous." Then followed an outflow of hot waters which dissolved and removed from the protoplasmic material silica, alumina, and potash, adding lime, magnesia, and soda, which " must have necessarily altered by degrees the composition of the porous mass, heated from below, pene­trated by aqueous solutions, and rendered more or less plastic in parts. In the changing mass, moreover, took place processes of crystallization, followed by partial separations determined by differences in specific gravity between the species thus formed. In this way were produced various types of plutonic rocks which may be justly called " Primary." T. Sterry Hunt would refer the crystalline Manhattan schists to these Primary rocks. As to the gentle folds {plica) so characteris­tic of these rocks, he said " decrease of volume beneath the crenitic covering (the area of the schists) must have resulted in movements giving rise to the more or less marked corruga­tions everywhere met with in the earlier layers of the crenitic envelope." Probably this view to-day would receive little more than an antiquarian attention.