GEOGRAPHY. 329 



connect with the astronomical station at Fort Bliss, Texas, 

 also connecting with the astronomical monument of the Mex- 

 ican Boundary Survey at El Paso, Texas, and the monument 

 on that part of the boundary-line on the western bank of the 

 Rio Grande. 



The following list shows the number of the principal ob- 

 servations made : 



Sextant latitude stations , 90 



Bases measured , r > 



Triangles about bases measured 64 



Main triangulation stations occupied G2 



Secondary " " " 21 



Miles measured on meanders 10,298 



Cistern barometer stations occupied 1,141 



Aneroid " " " 7,057 



Magnetic variations observed 1 Go 



Mining camps visited 12 



Mineral and thermal springs noted 20 



The estimated area occupied by the survey during the sea- 

 son, including main triangulation and preliminary reconnois- 

 sance work, was 35,000 square miles. The area from which 

 detailed topographical data were gathered sufficient for a 

 map on a scale of one inch to four miles was approximately 

 27,500 miles. 



Besides the topographical work, one party in the Colorado 

 section was devoted entirely to geological examination, un- 

 der the charge of Professor J. J. Stevenson, assisted by Mr. 

 J. C. Russell. Its area of operations was along the Spanish 

 ranges between the Rio Grande and Canadian rivers, in the 

 northern part of New Mexico, where its labors were greatly 

 facilitated by the use of the completed topographical maps. 

 The section of the lignitic group was worked out, and twen- 

 ty-six beds of lignitic coal were recognized as present at most 

 localities within the area where their horizon was reached. 

 Much labor Avas bestowed upon a study of the mountain 

 axes, the structure of which was found to be exceedingly 

 complicated, requiring further detailed examination. Quite 

 large collections were made of igneous rocks and fossils, about 

 three hundred specimens of the former being obtained from 

 seventy localities, forming a complete series illustrating the 

 lithology of the injected dikes, volcanic overflows, and ex- 

 tinct craters of the region. The fossils, numbering over thir- 



