The Highlands of the Black Forest in southern Germany exhibit a series of down-stepping benchlands with a sort of valley-in-valley grouping, which the late Walther Penck explained as the work of ordinary erosion on a domelike mass of continually accelerated upheaval; and this explanation has been widely accepted by German physiographers. The principles which led Penck to this view are here first stated, then analyzed. Several of them are shown to be erroneous. It is concluded that the Black Forest benchlands and valleys are better explained by erosion during intermittent upheaval, a kind of movement which Penck explicitly denied for the district he studied but which is ordinarily accepted by American physiographers for similar districts. Comments are added on the occurrence of what Penck called Primärrümpfe, on their relations to the cycle of erosion, on the difficulty of demonstrating their production and on the uncertainty of their occurrence.