Page:The National geographic magazine, volume 1.djvu/313

 the work any ordinarily intelligent person can do. A model may be as accurate as the map from which it is made, every contour may be placed exactly where it belongs, and yet the resulting model may be,—indeed, often is—"flat," expressionless, and unsatisfactory. Every topographer in drawing his map is compelled to generalize more or less, and it is fortunate for the map if this be done in the field instead of in the draughtsman's office. But topographers differ among themselves: there may be, and often is, considerable difference in two maps of the same region made by different men; in other words, the "personal equation" is a larger element in a map than is usually supposed. This being the case, there is something more required in a modeler than the mere transferring of the matter in the map,—giving it three dimensions instead of two: he must supply through his special knowledge of the region (or, failing that through his general knowledge) certain characteristics that do not appear upon the map, and undo, so far as it is necessary, certain generalizations of the topographer and draughtsman. This artistic or technical skill required correctly to represent the individuality of a given district is especially important in the modeler; it is more important, perhaps, in small-scale maps of large districts than in large-scale maps of small ones,—for in the latter the generalizing process has not been carried so far, and the smaller interval of the contour lines preserves much of the detail.

The methods by which relief maps are made have always received more attention than would, at first sight, appear to be their proper proportion. It may be due, however, to the difficulty of applying any test to determine the accuracy of the finished model, and perhaps also to the general impression that any one can make a relief map,—and so he can, though of course there will be a wide difference in the value of the results. Some, indeed, have devoted their attention to methods exclusively, letting the result take care of itself,—and the models show it. There is no more reason why a modeler should tie himself down to one method of work, than that a water-colorist, or a chemist, or anyone engaged in technical work, should do so; though in some cases he might be required, as the chemist is, to show his methods as well as his results.

One of the earliest methods, with any pretension to what we may term mechanical control, is that described by the Messrs. Harden in a paper on "The construction of maps in relief," read