ABSTRACT
The three decades we are about to discuss coincided with either the establishment or the enlargement of geological surveys in most civilized states. The prime purpose of the official surveys was the accurate mapping of exploitable areas in order to determine what rocks lay beneath the surface, but this naturally led to the inquiry as to how they had come to assume their present position and composition. The work necessarily involved paying attention to processes still active on the surface and the elaborate geologic memoirs published contained details notably of the sequence and thickness of strata and of the amount of strata removed by erosion, but also of the methods and rates of denudation and deposition. Imaginative inferences were gradually replaced by factual deductions and many theories acquired a sound factual basis. Not that in the past theories had been without facts, but about the mid-nineteenth century geological observations began to multiply at an ever-increasing rate. Geology was moving inexorably towards exactitude. Gone was the age of the speculator dreaming visions of cosmogonical chaos and creation from the security of a study chair.
