Page:The National geographic magazine, volume 1.djvu/318

 as his idea of it would be if he were on the real ground itself. Care should be taken, however, not to make the scales so disproportionate as to do violence to mental impressions. Often, indeed, prominent or important features, when they will bear it, may be still more effectively shown by additional exaggeration in the vertical scale." The fallacy of this argument is obvious. It assumes that the object of a model is to show the country as it appears to one passing through it, and not as it really is—and there is often a very wide difference between the two. The impression derived from passing through a country is, if I may use the term, a very large-scale impression, as any one who has tried it can certify; it is certainly a mistake to attempt to reproduce this impression in a small-scale model, with the help of vertical exaggeration. Even if the principle were a good one, its application would be very limited. It could only be used in large-scale models; to apply it to a model of a large area—the United States, for example—is obviously absurd.

The method referred to as being now generally in use may be briefly described as follows: requisites, a good contoured map; a hachured map in addition, if possible; a clear conception on the part of the modeler of the country to be represented; and a fair amount of skill. Materials: a base-board of wood or other suitable material; card-board or wood of the thickness required by the contour interval and the scale; and modeling wax or clay. Procedure reproduce the contours in the wood or other material; mount these upon the base-board in their proper relationship; then fill in the intervening spaces, and the space above the topmost contour, with the modeling material.

In a series of models of the Grand Divisions of the earth, made about a year and a half ago, the contours of card-board were made as follows: the map was photographed up to the required scale, and as many prints were made as there were contour intervals to be represented—in a model of the United States of 1,000 feet contour interval there were fourteen prints. Thirteen of these were mounted upon card-board of the exact thickness required by the vertical scale, and one upon the base-board. All large paper companies use a micrometer gauge, and card-board can easily be obtained of the exact thickness required—even to less than the thousandth part of an inch. The lowest contour was then sawed out upon a scroll saw, and placed upon the corresponding line of the map mounted upon the base-board. This