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, calling for more specialization, the professional geologist is now being called in to a larger extent than formerly. A logical trend also is the acquirement of more engineering training on the part of the geologist, for the purpose of pursuing these applications of his science.