This publication was written in 1926 during an era of heated discussions on continental drift based on an AAPG Symposium of the same topic. The problem of continental drift raised considerable and spirited discussion in geological circles. Many authorities advocated it; others were undecided but favorably inclined; still others did not favor it, and some of those were violently opposed. The mere possibility of continental drift was firmly denied by some during this era. It was not possible to settle the problem, or even to discuss it thoroughly in a single publication, but the main principles of the theory of drift are covered as are the main theories of the time, offering an intriguing glimpse into the history of geologic approaches to continental drift.