BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 2, BP. 177-188, PL. 6 FEBRUARY 12 1891 



GRAPHIC FIELD NOTES FOR AREAL GEOLOGY. 



BY BAILEY WILLIS. 



[Rcadhefore the Society December 30, 1890.) 



CONTENTS. 



Page. 



Importance of Kelations in Space to Geologic Studies 177 



Definition of an adequate Map for Geologic Purposes 178 



General Definition 178 



MeSods of Control 178 



Procedure with an inadequate Base 179 



The general Question 179 



Appalachian Work in the XJ. S. Geological Survey 180 



Stadia Transit Method 180 



Adoption of graphic Methods 181 



Summary of Methods 185 



Types of Field Notes 187 



Verbal descriptive Notes 187 



Verbal Notes for Stratigraphy 187 



Verbal Notes for horizontal Location 188 



Graphic Notes 188 



Importance of Relations in Space to Geologic Studies. 



Some years ago a coal property in Washington territory was offered for 

 sale by shrewd speculators, who valued the land at $1,100 an acre on 

 account of the great thickness of workable coal said to occur in several 

 veins. The property was not developed, but the number of coal beds and a 

 total thickness of good coal of more than one hundred feet were confidently 

 stated from exposures of the folded coal measures in a canon 400 feet deep, 

 which traversed a plateau whereon glacial drift and primeval forest ob- 

 scured the strata. Of these natural conditious the speculators skillfully took 

 advantage ; they opened the coal beds on the canon sides at points which 

 were not intervisible, and they cut a labyrinth of paths through the forest 

 leading from one opening to another. On the cliffs these paths were unpleas- 



XX Vll— Bull. Geol. Soc. Am., Vol. 2, 1890. (177) 



