CONTRIBUTIONS OF GEOLOGY 205 



was done along the French front. One series of maps con- 

 taining " General Information " carried overprints in colors 

 showing areas of resistant rock, sand soil, regions marshy in 

 wet seasons, regions permanently marshy, and other similar 

 data as to surface conditions. But these maps were imperfect, 

 and were not highly regarded by French geologists. 



At certain of the French Army Headquarters in the field 

 there were prepared and published real geological maps espe- 

 cially adapted to the needs of the army. Some of these maps 

 were made by trained geologists who happened to be in some 

 military service at the front, and secured appointment to do 

 a little geological work. Such maps were of course well made. 

 Others were prepared by men with little or no geological train- 

 ing, and quite naturally were full of errors. Those of the bet- 

 ter grade, for example one of the region about Rheims, were 

 well printed in a variety of colors, and were based on the' stand- 

 ard geologic map of France. The descriptions of the forma- 

 tions were in terms of military importance, and the color 

 scheme was altered so as best to portray data of this type in the 

 special locality concerned. Whether the soil was thin and 

 the rock resistant, or the soil deep and the rock decomposed; 

 whether the terrain was sandy, clayey, or marshy; whether it 

 was or was not adapted to trenches, dugouts, and other ex- 

 cavations; and whether such structures would remain long in 

 good condition or require constant repairs, were among the 

 items emphasized. Two separate columns were employed to 

 give the special characteristics of each formation, the one in 

 wet seasons, the other in dry seasons. A series of such maps 

 for the whole front would have been of inestimable value to 

 the French armies. 



Excellent use was indeed made of the standard French 

 geologic sheets by some of the engineering officers, who kept files 

 of these sheets at the front for constant reference. One of 

 these officers explained in detail how helpful the maps had been 

 in guiding him to horizons best adapted for tunneling, and 

 other underground works, and to formations valuable for road 



