The present memoir is simply a synopsis of facts observed by the author, with a few obvious inferences, touching the structure and classification of the older rocks of the Northwest. Citations will be made from other investigators where the facts or opinions appear to throw important light on the problems which the author has studied.
The motive for offering this presentation of the results of personal studies exists in the vague and conflicting state of opinion respecting the older rocks. This concerns not only their genesis and geological history, but their constitution and characters and even their sequence and mode of mechanical relation to each other. On the one hand, there are geologists of reputation who maintain that most granitic and gneissic rocks have originated directly from a state of molten fluidity; and this view is extended even to the so-called crystalline schists and . . .