Page:The Journal of geology (IA journalofgeology21894univers).pdf/104

for collegiate work. But in the laboratory, numerous maps, views, or models may be exposed on walls, racks, or tables, remaining for a week together, and thus giving abundant time for deliberate examination. From week to week a change may be made in the materials, the group for each week corresponding to the group of problems then in hand. Many of the illustrations shown in the first week are repeatedly brought forth again later in the course, always gaining new meaning as sharper outsight and insight are directed to them. Many facts of interest concerning population and occupations may be brought forward in this connection; but it is important that the geographical facts should first be clearly apprehended.

In the reports that are made on this laboratory work, the students first describe the facts that they have observed, in terms that have no suggestion of explanation. They should not say that a certain region is a baselevelled surface; but that it is a lowland of faint relief. They should not at first speak of old rivers revived into a second youth; but they may say that the rivers of a certain region run in deep, narrow valleys below an upland of generally uniform altitude, above which occasional isolated hills rise to greater elevations. This I regard as extremely important, in order to ensure a careful observation of the facts in discussion; for until the facts are clearly perceived they cannot be precisely explained. It is unsafe at first even to speak of the flat region at the mouth of a river as a delta. This term not only denotes the form of the surface but connotes an explanation; and in the earlier weeks of the study it is by no means sure that the observer fully perceives all the facts of form that are denoted by the term, or that he fully appreciates all the features of the process that are connoted in its explanation. The outbranching of the distributaries near the river mouth as contrasted with the inbranching of the tributaries (or contributaries, as they might be called), further up stream; and the faintly convex form of the delta surface as contrasted with the concave form of the upper valley may not be clearly observed, unless they are concisely formulated in a description. The essentially bal-