178 The American Geologist. September, lsos. 
MODERN RATIONAL RELIEF OF THE 
EARTH'S SURFACE. 
Abstract of a paper delivered before the American Association for the 
Advancement of Science. 
By George Carroll Curtis. 
The Paris Exposition of 1900 afforded a comparison of the 
world's work in representing its surface in actual relief. It 
was evident to the observer that in the broader and more ra- 
tional methods, the United States fell below some of the coun- 
tries of Europe in this work. It is the object of this paper to 
consider some of the possibilities of "relief maps" and to en- 
deavor to point out a course by which American work may be 
advanced upon more rational lines. 
In possessing the third dimension of thickness, the model 
is lifted beyond the limitations of arbitrary convention, which 
must ever make the map an artificial means. A perfect relief 
map would be a perfect miniature or model of nature, and on 
the scale of nature direct casts might in some instances be 
taken from the field. Truthful topographic modelling is there- 
fore an exact art requiring accurate, systematic and rational 
methods throughout, gathering a data upon the field, and its 
application and reproduction in other dimensions. Modern 
inventions, including "dry-plate" photography, contour maps 
and the interpretation of topographic forms, which the late 
advance in geographic science has given, are potent aids in 
and largely accountable for the rational development of this 
most truthful and expressive of known means for representing 
the configuration of the earth. 
There are two methods of representing topography in re- 
lief, the mechanical, and the rational or truthful, and they are 
so distinct in requirements, process, and results, and their de- 
mands are so fundamentally different, that they should by 
rights conflict in no way with each other. If it is desired to 
make a conventional mechanical "relief" and it is considered 
worth while and consistent to employ the truthful medium of 
three dimensions, rather than the uncompromising one of the 
shaded map, no objection can be reasonably offered, though the 
naturalist may regard such empirical work as unprogressive. 
It is when this mechanical construction is made to assume the 
