IT has been well remarked by Humboldt* that to behold is not necessarily to observe, that is, to compare and combine. The history of Geology, like that of all sciences depending for their effective advance on experiment or correct observation, amply proves the truth of this statement. We are not required to look far back to be fully aware of the many brilliant hypotheses which have given way before the advance of correct research. It was not that these brilliant hypotheses were intended as substitutes for sound geological knowledge, based on correct data, or that those who formed them were not as capable as any who may in aftertimes succeed in still farther systematically embodying the accumulated data of such times, but merely that correct observations were not then sufficiently abundant, and that powerful, and, sometimes, impatient minds supplied their place with conceptions more captivating than well founded. It is obvious that with a hundred well-established facts more can be accomplished than with ten, the deductions from which, however apparently correct, may even be fallacious as respects those derived from the consideration of the greater number. Let it not, nevertheless, be hastily concluded that the views which have passed away have not materially advanced geology, as those of a similar character have aided the progress of other sciences. Without them, though a few may have been impediments for the time, many a subject would have longer remained disregarded by its zealous investigator. Even the controversies which have from time to time appeared, many from differences of opinion arising the more readily as the subject was