Page:The National geographic magazine, volume 1.djvu/317

 ter that its relief, in all its detail, cannot be shown upon a scale of 6 inches to 1 mile without any exaggeration at all.

It seems to me that the absolute and not the relative amount of relief is the desideratum, and I have always used this as my guiding principle. For small scale models I have found half an inch of relief ample. It may be worth while to state that in a model of the United States made for the Messrs. Butler, of Philadelphia, the horizontal scale was 77 miles to 1 inch, the vertical scale 40,000 feet to 1 inch, and the proportion of scales as 1 to 10. This proportion could have been brought down as low as 1:6 with advantage. One-fortieth of an inch to a thousand feet seems a very small vertical scale, but it sufficed to show all the important features of the relief. It should be stated, moreover, that the model in question was very hurriedly made—in fact, was hardly more than a sketch-model—and that more care and more minute work would have brought out many details that do not now appear. This amount of care was not considered necessary in this instance, as the model was made to be photographed and published as a photo-engraving, and was to suffer an enormous reduction coming down to five by seven inches.

It has been frequently urged by the advocates of large exaggeration that the details of a country cannot be shown unless the vertical scale is exaggerated; that hills 200, 300, or even 500 feet high—depending of course upon the scale—flatten out or disappear entirely. This seems plausible, but the advantangesadvantages [sic] of great exaggeration are more apparent than real. Its effect upon the model has already been mentioned; it should be added that, with the proper amount of care in finishing the model, exceedingly small relief can be so brought out as to be readily seen. With ordinary care, one-fortieth of an inch can be easily shown, and with great care and skill certainly one-eightieth and probably one-hundredth of an inch. Another plausible argument that has been advanced in favor of vertical exaggeration as a principle, is well stated by Mr. A. E. Lehman, of the Pennsylvania Geological Survey, in a paper on "Topographical Models," read before the American Institute of Mining Engineers in 1885. "A perfectly natural expression is of course desired; and to cause this the features of the topography should be distorted and exaggerated in vertical scale just enough to produce the same effect on the beholder or student of the district of country exhibited