During the past quarter-century the cleavage in the ranks of geologists, brought about by Ramsay’s classic paper, has remained. Fairchild and others in America, Heim, Bonney, and Garwood in Europe argue for insignificant erosion by glaciers; and Gannet, Davis, Gilbert, Tarr in America followed by Austrian workers present evidence for erosion on a gigantic scale. A perusal of the voluminous literature in the Journal and elsewhere shows that the difference of opinion is in part one of terms, the amount of erosion rather than the fact of erosion; it also arises from failure to differentiate the work of mountain glaciers and continental ice sheets, of Pleistocene glaciers and their present diminished representatives. The irrelevant contribution of physicists has also made for confusion. It is interesting to note that the criteria for erosion of valleys by glaciers has long been established and by workers in different countries. Ramsay (1862) in England outlined the problem and presented generalized evidence. Hector (1863) in New Zealand pointed out the significance of discordant drainage, the “hanging valleys” of Gilbert. The U-form, the broad lake-dotted floor, and the presence of cirques and the process of plucking were probably first described by LeConte (1873) in America. The truncation of valley spurs by glaciers pointed out by Studer in the Kerguelen Islands (1878) was used by Chamberlin (1883) as evidence of glacial scouring. _Conclusion._ During the past century many principles of land sculpture have emerged from the fog of intellectual speculation and unorganized observation and taken their place among generally accepted truths. Many of them are no longer subjects of controversy. Erosion has found its place as a major geologic agent and has given a new conception of natural scenery. Lofty mountains are no longer “ancient as the sun,” they are youthful features in process of dissection; valleys and canyons are the work of streams and glaciers; fiords are erosion forms; waterfalls and lakes are features in process of elimination; many plains and plateaus owe their form and position to long-continued denudation. Modern landscapes are no longer viewed as original features or the product of a single agent acting at a particular time, but as ephemeral forms which owe their present appearance to their age and the particular forces at work upon them as well as to their original structure. It is interesting to note the halting steps leading to the present viewpoint, to find that decades elapsed between the formulation of a theory or the recording of significant facts and their final acceptance or rejection, and to realize that the organization of principles and observations into a science of physiography has been the work of the present generation. Progress has been conditioned by a number of factors besides the intellectual ability of individual workers.