Page:Popular Science Monthly Volume 55.djvu/478

460 in the section under consideration formed the subject of a separate lesson, in which its structural features and the more important events of its history were presented. Special attention was given to tracing the relations of the existing surface features of each district to its geological structure, thus connecting the physical geography and geology of the region. These lectures were based on a large amount of original investigation and results reached by Professor Crosby in his studies of the Boston basin."

During the winter of 1886-'87 Prof. W. M. Davis delivered a course on Problems in Physical Geographic Classification, treated of in two lessons, and the Laws of the Evolution of the Principal Topographical Types occupied the remainder of the course. Professor Davis gave the class the benefit of the results of his investigations, which were original contributions of importance to the progress of physical geography. "The graphic manner of illustrating the lessons upon the Glacial period and the effects of the great glacier upon the area of the Great Lakes was very effective. This was shown by means of a relief model whose surface was composed of an ingenious arrangement of overlying and differently painted surfaces. by removing these in succession the lecturer traced the whole history of changes following upon the recession of a continental glacier and its effects upon the surface waters. . . . These lessons were so novel and useful to teachers that he was invited to give a course of ten lesions during the next winter upon the physical geography of the United States. New matter, new models, and more extended illustrations were used in this course. The objects of the course were: To illustrate the value of systematic classification in the study of physical geography in order that forms of similar origin might be grouped together; to advocate the importance of studying the evolution of geographic forms in time, so that forms similar in origin but dissimilar in ace