that the continents look like they could "fit" together, much like puzzle pieces that have drifted apart. Then, he noticed that when you put the continental puzzle pieces back together, other things started to fit. For example, the rock layers that form the Appalachian mountains of the eastern U.S. matched quite well with those in Scotland. Thus, he concluded that the continents must 'drift' around the Earth, occasionally colliding with one another.
