Introduction. Usually the presence of a conglomerate in a stratigraphic series of rocks is a matter of considerable importance to the geologist. He naturally infers the presence of a break in the continuity of sedimentation; an orographic movement of greater or less extent; erosion of a preexisting formation. He sees, in his mental review, the waves sorting and depositing sand, pebbles and bowlders derived from the uplifted land. The idea of the lapse of a period of time of considerable and often long duration is formed as he recalls orographic movement, erosion and unconformity of deposition. If the conglomerate is near the base of some formation or series of formations, he views it as almost conclusive evidence of the marked change that introduced the new deposits. This is all fair induction from observed facts, and it is the general and approved experience of geologists. When I ventured to describe to . . .
- © 1893 Geological Society of America