The First Strata. It was just preceding the last uplift of this epoch that the era of deposition of rock debris was so prolonged that twelve thousand feet of strata were washed into the bed of the sea, in the region now known as the Grand Canyon Country. It was at the time when life was beginning to dawn, for in the remnants of the strata are found fossils of the earliest known life. These strata, therefore, are of immense interest to the geologist, as they are the first known rocks containing life to emerge from the primeval sea. Within the last few years, they have been called the Algonkian Series, and later I shall speak of them more freely.

Prior to the deposition of these Algonkian strata, the Laurentian rocks (the granite) upon which they rest were subject to a long period of "planation,"--as the grinding down and leveling of rock surfaces is termed. After this planation was complete, a subsidence occurred; the whole area became the bed of an inland sea, and upon the planed-down granite, the debris that formed the Algonkian strata was washed.