This oration is introduction to the next series of Harvard experiments, which dealt with squeezing and wrinkling strata in imitation of the folds and faults of the Appalachian Mountains. Bailey Willis, at the Geological Survey, made a press of wax models of strata. A heavy oak piston was advanced by a screw crank. The models were waxes mixed with plaster for hard strata and waxes mixed with Venice turpentine for soft strata. They were cast to imitate actual successions of hard, thick limestones; less hard sandstones; soft mudstones; or slates. The piston advanced at a measured rate against one end of the model, the other end being a fixed box, the strata lying horizontally. The elongate Appalachian basin had a continent (the piston) to the east; a wide flat fill of limestones or sea bottom to the west (the box); and the deepest trough of pebbles, sands, and muds on the east, toward the rivers of the eroding continent of that ancient time. The heavy limestone tapered from the west into these thinner beds and made a stiff rib in their midst. The final result of their wrinkling was linear folds with axes north and south parallel to the trough, and close set at the east. The folds overturned toward the west, the overturns developing into overthrust fractures westward when the beds ruptured. Also, the folds became bigger, flatter, and wider apart westward under the deeper sea, the famous one being the Cincinnati arch. The evidence in the middle eastern states is that the trough bottom sank as the heavy shore sediments were dumped by rivers into the sea. The west-central states received a wide flat of limestone. Uplift of the continent shallowed the ocean and pushed it, narrower, over to the great plains. So there were left a deep trough of weak beds, a massive limestone, and an overlap of continental wash across the uplifted later continent of the present time. The problems to be studied in Willis’ models were how folding would affect such a pile, what transmitted the wrinkling force, what started a single fold, and how soft and hard strata behaved under horizontal pressure. He found that hard, thick layers of limestone transmitted the push farthest. That soft beds piled up on each other near the piston. That these beds showed beautiful overthrust faults inclined away from the piston. And that the start of individual folds was favored by very small initial bends in a transmitting layer. These downbends away from the continent would be made as the trough bottom sank through the ages. The nature of this sinking in upright slices of the bottom rock is probably downfaulting. Each vertical slice would make a step-bend as it sank.