522 REPORT UNITED STATES GEOLOGICAL SURVEY. 



three times as much. The total number of stations made was 340, and 

 the area surveyed, as already stated, was 13,000 square miles. 



In this chapter I have endeavored to give a general idea of the dis- 

 trict, and in the succeeding ones will present the details obtained, and 

 conclude with the special consideration of the geological formations 

 noted as occurring in the district. 



From the fact that the area examined was so large the results are 

 somewhat incomplete in detail, the general features claiming attention 

 first. The plan of working with the topographer from the high stations 

 from which extensive views of the country are obtained, and of general- 

 izing from these stations the more detailed data obtained along the line 

 of march, and using the topographical locations, insures greater accu- 

 racy and rapidity in the work than could be obtained were the geologist 

 to devote his time to detailed work in the ravines and gulches, especially 

 in a country of which there are no existing maps that are sufficiently 

 correct to delineate the geology. The nature of the country also facili- 

 tates this mode of working, as it is generally bare of dense timber, the 

 vegetation being scanty and erosion having so exposed the rocks that 

 the conditions of the strata are easily seen, and the geological structure 

 of the country for many miles around the station readily recognized. 



The geological map is therefore colored with a considerable degree of 

 accuracy, although much may be left for future investigation in the way 

 of detail, as the geologist is necessarily unable to visit every point in 

 his district, notwithstanding the fact that he has overlooked his entire 

 area from the stations. 



