AND THE ADJACENT COUNTRY. 167 
and the river Colorado, and not by land, without the 
express consent of the Mexican government.” 
The United States government, knowing that oppor- 
tunities would be presented, in the course of the exten- 
sive surveys intrusted to me, to acquire important 
geographical knowledge relating to the immense 
frontier along the line to be explored and surveyed, 
fully authorized me to seek such facts. In his instruc- 
tions to me, the Hon. Secretary of the Interior says: 
‘As the organization of the Commission under your 
charge has been made for the purpose of collecting 
information relative to the country contiguous to the 
boundary line, in addition to the running of that line, 
itis desirable that you should avail yourself of every 
opportunity afforded by your passage through the 
unexplored regions of Texas, New Mexico, and Cali- 
fornia, to acquire information as to its geography, 
natural history, &c., when it can be obtained without 
retarding the progress of the Survey.” * My duties 
required me to send boats to the mouth of the Gila to 
survey that portion of the river, as well as to carry 
provisions there for the surveying parties ; and I should 
have been guilty of neglect had I not endeavored to 
take advantage of this opportunity to examine the 
upper part of the gulf, and that portion of the Colo- 
rado between its mouth and the junction with the 
Gila. A minute survey of the entire gulf, about 
which Colonel Graham has made calculations, was not 
contemplated by either Lieutenant Strain or myself. 
The great obstacle to the ascent of the Colorado is 
* See Instructions, Appendix. 
