332 proceedings: Washington academy of sciences 



of engineering structures, etc., and in determining the sources of water, 

 road metal, etc. It will be evident that as both strateg>^ and tactics 

 must take account of the physical features of the terrain all great 

 military leaders have made at least a subconscious use of geologic 

 facts. Most of them have, however, failed to recognize that geology 

 makes it possible to predict, often with a high degree of accuracy, the 

 physical conditions that influence and often control certain military 

 operations. 



Any engineering project involving excavation must take account of 

 the underground physical conditions, or, in other words, of the geology. 

 This is specially true of fortifications, for protection against modern 

 high-power artillery cannot be obtained by surface structures no matter 

 how strongly built. Adequate cover demands deep works protected 

 by virgin ground. The deeper the excavation the greater the geologic 

 control. Even the construction of the relatively shallow trenches, 

 however, is to a great extent controlled by geology. In these the depth 

 to hard rock, the permeability of the soil, and the stability of the slopes 

 are important and often decisive factors. There are many examples 

 during the late war where positions have been lost and lives sacrificed 

 because of the ignorance of commanding officers of the fact that en- 

 trenchment was impossible at the selected site within the time and with 

 the equipment available. Again, many dugouts have been built 

 only to be useless because of flooding by underground water. In most 

 cases such blunders could have been avoided with only an elementary 

 knowledge of local geology. Military mining is usually impossible 

 where geologic conditions are unfavorable, yet no mention of this fact 

 is made in the many manuals devoted to this subject. 



Geologic facts, together with those relating to seasonal precipitation, 

 also serve in the classification of the terrain with reference to the physical 

 conditions of surface, which determine its passableness for infantry, 

 artillery and tanks. A land surface that would have been no obstacle 

 in former wars, with their relatively small number of troops and light 

 equipment, might prove almost impassable to the great concentration 

 of men and heavy artillery and tanks demanded by present tactics. 



The supplying of the huge modern armies with water is one of the 

 largest tasks of the military engineer. The great utility of geology in 

 this field needs no argument. Geology also finds an important use in 

 helping to locate sources of road metal and other structural materials. 

 The principal subjects in which geology may be of military service are 

 summarized as follows: 



I. Field works. (Trenches, dugouts, and mines.) 



1 . Siting of field works. Location will take advantage of .favorable 

 geologic conditions as far as tactical situation permits. 



2. Trenches. Physical character of material to be excavated; 

 depth to hard rock; stability of slopes; surface drainage; under- 

 ground water. 



3. Dugouts and mines. Lithology and structure of rocks; ground 

 water; water-bearing strata. 



