The following paper is adapted from a partly written treatise on the subject of metamorphism and the metamorphic rocks. In this article I shall summarize some of the more important physical and chemical principles which concern the alterations of rocks, and shall apply these principles to the alterations which occur in connection with dynamic action.
The agents through which the alterations of rocks take place are water solutions and mineralizers. In the present discussion mineralizers will not be considered.
Below the level of the free surface of underground water the rocks are practically saturated; above that level the rocks are not ordinarily saturated, but upon the average contain a considerable amount of water held by adhesion between the liquid and the solid mineral particles. Both below and above the free surface water is the all-prevailing agent through which the chief alterations of rocks are accomplished. . . .