Page:Popular Science Monthly Volume 78.djvu/241

Rh of which must come upon the stage at the proper time, play its part in the most effective manner, and then retire in favor of the next player. Yet while thus bringing forth the objective elements of the problem as clearly as possible, it is still entirely permissible for the speaker occasionally to speak for himself, in short interludes, as it were, and thus to interject some interesting personal story regarding the discovery of important facts; or to tell of the surprise and delight that he felt at the moment when a happy invention sprang unexpectedly into his mind; or to describe the excitement that he experienced when, on returning to the field in order to determine whether previously unnoticed facts really occurred as the deduced consequences of a certain hypothesis had led him to expect they should, he found one item after another at its appointed place and in its predicted form. But all this personal part should be played simply, without "heroics," so that the attention of the hearers shall not be too much withdrawn from the problem under discussion, or from the conclusion which it reaches.

The Systematic Method.—This method is adapted to the presentation of groups of allied facts in a classified order, according to their kind, and independent of where they occur; it is thus contrasted with regional presentation, which treats all the things that occur in a single district or region, whatever their kind. Attention is given in systematic presentation to the likenesses and differences of allied objects, these likenesses and differences being described either in an empirical or in an explanatory manner. If explanatory descriptions are adopted, the explanations on which they are based should have been previously established by induction or by analysis, and here used as already demonstrated and familiar, so that attention shall be now directed to the classification of the things that are explained, and not to the proof of their explanation: thus, however geological the analytical investigations of a student of geography may have been for a time, their truly geographical object is now set forth. Hence systematic presentation is of a grade that follows inductive and analytical presentation and precedes regional.

The kinds of things appropriate for presentation in classified order by the systematic method may be any group of forms, possessing associated similarities or related differences in structure, in process of carving, or in stage of development, and hence in form. They may be large features like plateaus and mountains or small details like river or valley meanders; but in either case they should be arranged according to the accepted principles of scientific classification, and the plan of classification should be explicitly announced. It is here important to recognize that the explanatory treatment of land forms by the aid of deduction enables one to complete the systematic classification of many forms, that would be very imperfectly treated if a purely