And one of the things he had observed is that if you look at mountains like the Appalachians, you often find that the rocks in them are folded, and they're folded in a particular way, which suggested to him that they were actually being compressed from the side.
Uma das coisas que observou foi que, se olharmos para montanhas como os Apalaches, descobrimos que as suas rochas estão dobradas de um modo especial que lhe sugeriu que estavam a ser  comprimidas lateralmente.