The
location of best sources of supply for ballast is also a geologic
problem (see pp. 90-91).

The physiographic phases of geology also are finding important
applications to railroad building. The physiographer studies the surface
forms with a trained eye, which sees them not as lawless or
heterogeneous units but as parts of a topographic system, and he is able
to eliminate much unnecessary work in the location of trial routes.
Further study of some of the older railroads from this standpoint has
led to considerable improvements. Physiographic study has also been
applied to railway bridge construction, in the appraisal of the
difficulties in surmounting stream barriers. A still broader use of
physiography or geography, not popularly understood, is illustrated in
the case of certain transcontinental railroads, in the study of the
probable future development of the territory to be served--many features
of which can be predicted with some accuracy from a study of the rocks,
soils, topography, conditions of transportation, and natural conditions
favoring localization of cities. The location of new towns in some cases
has been based on this kind of preliminary study.

In locating an Alaskan railway close to the end of a momentarily
quiescent glacier, troubles were not long in appearing, due to the fact
that the glacier was really not as stable as it seemed to the layman. A
specialist on glaciers, knowing their behavior, their relations to
precipitation, their relations to earthquakes, the speed of their
movement, and the periodicity of their movement, was ultimately called
into consultation on the location of the railroad.

ROAD BUILDING

Road building in recent years has become a stupendous engineering
undertaking, which is requiring geologic aid to locate nearby sources of
supply for road materials. A considerable number of geologists are now
devoting their attention to this work. It relates not only to the
hard-rock geology but to the gravel and surface geology. Certain
northern states are using specialists in glacial geology to aid in
locating proper supplies of sand and gravel.

GEOLOGY IN ENGINEERING COURSES

Many engineering courses include elementary geologic studies, in
recognition of the close relationship between geology and engineering.
Men so trained, though not geologists, have been responsible for many
applications of geology to engineering. With the increasing size and
importance of operations, c