90 THE JOURNAL OF GEOLOGY. 



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 corres- 

 ponding 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 inter- 

 est concerning population and occupations may be brought for- 

 ward 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 con- 

 trasted with the inbranching of the tributaries (or contributaries, 

 as they might be called), further up stream ; and the faintly con- 

 vex 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- 



