EXPLANATORY NOTE TO GEOLOGICAL REPORT. 
Washington, February 18, 1857. 
The mineralogical collections made by me were placed in the hands of M. Jules Marcou for 
examination, and carried by him to France. They were subsequently returned in a confused 
condition, and with many of the labels displaced. This fact will account for many errors in 
the report, map, and section prepared by Mr. Blake. 
JOHN POPE, 
Captain Topographical Engineers. 
