6 



II. E. Gregory — A Geologic Reconnaissance 



tions are subject to considerable error. To reduce this error as 

 much as possible, and to prevent the accumulation of errors of 

 elevation, I ran a line of levels down the railroad from Cuzco 

 to the ends of the base line and then with vertical angles and 

 the computed distances of the transit triangulation found the 

 elevations of Ccorao and Picol, on the north side of the valley, 

 and Huanacapria, on the south side. Then, in making plane- 

 table stations I was able to get a fairly flat vertical angle to 



Fig. 1. 



Fig. 1. Areas surveyed by members of tbe Peruvian Expedition of 

 1912, — A, A. H. Bumstead; B, A. H. Bumstead and Robert Stephenson; 

 C, Robert Stephenson. Cities mapped by J. P. Little. Osgood Hardy acted 

 as Mr. Bumstead's assistant throughout. 



some one of these points, or to points of known elevation along 

 the railroad. I soon had a considerable number of points scattered 

 about the sheet, whose elevations were well determined and 

 checked, and from these I always worked." 



The area marked B is mapped from a reconnaissance survey 

 by Mr. Bumstead and Mr. Stephenson, following the methods 

 adopted for area A. The streets of Cuzco, San Sebastian and 

 San Greronimo were surveyed by Mr. J. P. Little, topographic 

 assistant; the plats of Oropesa, Lucre, and other villages are 

 generalized. Time did not permit the tracing of trails, and 

 therefore many important ones are not shown. 



