Topog7'aphic Models. 261 



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 Phil- 

 adelphia, 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 exag- 

 geration 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 dis- 

 appear entirely. This seems plausible, but the advantanges 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, exceed- 

 ingly 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 princi- 

 ple, 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 exag- 

 gerated in vertical scale just enough to produce the same effect 

 on the beholder or student of the district of country exhibited 



*See plate from " Butler's Complete Geography." 



