48 ILLINOIS ACADEMY OF SCIENCE 



Wasliiiigton and capable of producing nearly 1,000,000 

 maps each month was erected and operated. Many of the 

 maps were revised and reissued daily. As a result, all 

 officers now realize as never before the dependence of an 

 army on topographic maps. 



Eelated to map-making was the building of relief mod- 

 els. These were used in studying the visibility of the 

 country from observation posts; and assisted in control- 

 ling shell-fire on enemy targets. Finished models showing 

 relief and villages and roads were made by the thousands, 

 and in the remarkable time of a few hours for each original 

 mold, after which any number of fac similes could be 

 made quickly. 



Another vital need of the army was an enormous supply 

 of water for men and horses, for concrete construction 

 work, and for power plants and locomotives. Geologists 

 made maps showing locations of springs and of shallow 

 and deep water-bearing rocks. They also supervised the 

 boring of wells, especially in the British army. 



Supplies of rock, gravel, and sand were also needed in 

 large amounts for building roads, gun foundations, dug- 

 outs, supply depots, and harbor w^orks. Geologists assisted 

 in locating the material. 



Finally, maps and diagrams were made of the rock 

 formations along the lines held by our army, and by the 

 enemy, in order to show their suitability for the construc- 

 tion of trenches, dugouts, and mines. It was possible to 

 observe existing works, and then to predict the conditions 

 in new areas which were geologically similar. Thus, it was 

 possible to say in advance whether trenches would stand 

 without revetment of the walls ; whether they would be wet 

 or dry during certain seasons ;and to advise regarding tools 

 which would be needed to construct defensive works. Maps 

 were prepared to show the probable effect of artillery fire 

 on the formations ; thus, whether the rocks would shatter 

 and add to the casualties ; and whether barrage fire would 

 make the ground impassable for tanks. 



These various uses for geologists in direct warfare were 

 developed by the allied armies in varying degrees, but the 

 Germans had prepared a systematic organization in ad- 

 vance, or at an early date. Our geologists and geographers 



