46 National Geographic Magazine. 
as it is only through these surveys their availability will be made 
manifest, the importance of the work can hardly be overestimated. 
The prosperity of several states will be largely influenced by the 
success of operations of this kind within their borders, and in turn 
their greater development and increased wealth, must react upon 
the older communities and benefit them, on the principle that the 
healthful growth of a single member is strength to all. 
The science of geography, as taught in the present day, is more 
comprehensive than the brief descriptions and delineations of the 
areas of land and water that satisfied the early explorers. The 
great strides that have been made in scientific research during the 
past century have opened new fields, and men are no longer con- 
tent to picture that only which they can see. The varied fea- 
tures of the earth’s surface, transformations now in progress and 
those which may be deduced from the facts we can observe, have 
led to many theories of the construction of the earth, ancient 
forms upon the surface and possibilities, if not probabilities, in 
the future. To ascertain the form of the earth has alone been the 
cause of heroic labor, and yet we have hardly passed the point 
that we can give it in probable terms with the general dimen- 
sions. Observations warrant the assumption that, discarding the 
accidents of nature—even the highést mountains—the sphere is 
far from being perfect. That it is flattened at the poles is now 
accepted as the true condition, but we have reason to believe, too, 
that this is not the only departure from the perfect sphere. The 
more thorough the research and precise the observations, the 
more certain does it appear that the crust has a form as though 
there had been great waves of matter that had been solidified, 
To locate the depressions of these great waves and measure their 
depths, to pomt to the crests and measure their extent, is a 
problem for the future to solve. Their study is claimed to be 
within the legitimate sphere of geography ; and not until they 
have been satisfactorily answered can we assert the geographer 
is even approaching the end of the facts his science has yet to 
utilize. 
In pre-historic geography we have had two papers presented 
to the Society during the past year, relating to the orographiec 
features of the earth’s surface in times past compared with the 
localities as we may see them to-day. In the first instance the — 
comparison is evolved from an effort to trace the origin and 
growth of the rivers of Pennsylvania; and the second, in a 
