While the activities of geologists for government, state, and private organizations were for the most part in relation to mineral resource questions, this was by no means the total contribution. The U. S. Geological Survey and other organizations, in coöperation with the War Department, did a large amount of topographic and geologic mapping of the eastern areas for coast-defense purposes. This work involved consideration of the topography for strategic purposes, as well as the stock-taking of mineral resources—including road materials and water supplies. The revision of Geological Survey folios, with these requirements in mind, brought results which should be of practical use in peace time. Studies were likewise made of cantonment areas, with reference to water supplies and to surface and sub-surface conditions.
Many geologists were engaged in the military camps at home and abroad, and in connection with the Student Army Training Corps at the universities, in teaching the elements of map making, map interpretation, water supply, rock and soil conditions in relation to trenching, and other phases of geology in their relation to military operations. The textbook on Military Geology,[61] prepared in coöperation by a dozen or more geologists for use in the courses of the Student Army Training Corps, is an admirable text on several phases of applied geology. The name of the book is perhaps now unfortunate, because most of it is quite as well adapted to peace conditions as to those of war. There is no textbook of applied geology which covers certain phases of the work in a more effective and modern way. The topics treated in this book are rocks, rock weathering, streams, lakes and swamps, water supply, land forms, map reading and map interpretation, and economic relations and economic uses of minerals. Another book,[62] on land forms in France, prepared from a physiographic standpoint, was a highly useful general survey of topographic features and was widely used by officers and others.
GEOLOGY AT THE FRONT[63]
Perhaps the most spectacular and the best known use of geology in the war was at and near the front. This use reached its earliest and highest development in the German army, but later was applied effectively by the British and British Colonial armies, and by the American Expeditionary Force.
One of the first intimations to the American public of the use of geology at the front appeared in the publication of German censorship rules in 1918,—when, among the prohibitions, there was one forbidding public reference to the use of earth sciences in military operations. A leading American paper noted this item and speculated at some length editorially as to what it meant.
It was discovered that geologists to the number of perhaps a hundred and fifty were used by the Germans to prepare and interpret maps of the front for the use of officers. Features represented on these maps included topography; the kinds of rocks and their distribution; their usefulness as road and cement materials; their adaptability for trench digging, and the kinds and shapes of trenches possible in the different rocks; the manner in which material thrown out in trenching would lie under weathering; the ground-water conditions, and particularly the depth below the surface of the water table at different times of the year and in different rocks and soils; the relation of the ground-water to possibilities of trench digging; water supplies for drinking purposes; the behavior of the rocks under explosives, and the resistance of the ground to shell-penetration; the underground geological conditions bearing on tunnelling and underground mines; and the electrical conductivity of rocks of different types, presumably in connection with sound-detection devices and groundings of electric circuits. Some of the captured German maps were models of applied geology. They contained condensed summaries of most of the features above named, together with appropriate sketches and sections. During the Argonne offensive by the American army the captured German lines disclosed geologic stations at frequent intervals, each with a full equipment of maps relating to that part of the front. From these stations schools of instruction had been conducted for the officers in the adjacent parts of the front.
The British efforts were along similar lines, although they came late in the war, under the leadership of an Australian geologist. Their efforts were especially useful in connection with the large amount of tunnelling and mining done on the British front. Among the many unexpected and special uses of geology might be cited the microscopical identification of raw materials used in the German cement. It became necessary for certain purposes to know where these came from. The microscope disclosed a certain volcanic rock known to be found in only one locality. In the Palestine campaign, the knowledge of sources of road material and water supply based on geologic data was an important element in the advance over this arid region. Wells were drilled and water pipes laid in accordance with prearranged plans.
In spite of the fact that the usefulness of geology had been clearly indicated by the experience of the German and British armies, the American Expeditionary Force was slow to avail itself in large measure of this tool; but after some delay a geologic service was started on somewhat similar lines under the efficient leadership of Lieutenant-Colonel Alfred H. Brooks, Director of the Division of Alaskan Resources in the U. S. Geological Survey. The work was organized in September, 1917, and during the succeeding ten months included only two officers and one clerk. For the last two months preceding the armistice there was an average of four geologic officers on the General Staff, in addition to geologists attached to engineering units engaged in road building and cement making, and plans had been approved for a considerable enlargement of the geologic force. The work was devoted to the collection and presentation of geologic data relating to (1) field works; (2) water supply; and (3) road material. Of these the first two received the most attention. Maps were prepared, based somewhat on the German model, for the French defenses of the Vosges and Lorraine sectors, and for the German defenses of the St. Mihiel, Pont-a-Mousson, and Vosges sectors. Water supply reports covered nearly 15,000 square kilometers. The following description of the formations, taken from the legend of one of the geologic maps, shows the nature of the data collected:
Silt, clay and mud, with some limestone gravel, usually more or less saturated, except during dry season (June to September), in many places subject to flooding. Surface usually soft except during Summer. These deposits are ½ to 2 meters thick in the small valleys, and 2 to 3 meters in the —— Valleys. Unfavorable to all field works on account of ground-water and floods, and not thick enough for cave shelters.
Silts with some clay and fine sands and locally some fine gravel and rock débris. These deposits occur principally on summits and slopes, and are probably from 1 to 2 meters thick. Even during dry season (June to September) they retain moisture and afford rather soft ground. In wet season the formation is very soft and often muddy. In many places water occurs along bottom of these deposits. Favorable for trenches, but which require complete revetment, and ample provision for drainage, not thick enough for cave shelters; cut and cover most practical type of shelter.