28 
CIRCUMSTANCES UNDER WHICH THIS RECONNAISSANCE WAS CONDUCTED. 
use of Indian presents, and to the habit of constantly seeking the hospitality of the Indian 
camps. 
All examinations of reconnaissance upon the more northern exploration to Puget Sound had 
been connected with a base line, the position of which may hereafter he determined by instru¬ 
mental observations. Those,of which the present report is the result, were connected with the 
line of the great emigrant trail to Oregon and California, and with positions defined by topo¬ 
graphical surveys. 
A series of meteorological observations were conducted from Columbia river to the mouth of 
the Port Neuf river,,(establishing the relative 'height of mountain passes and great planes of 
surface of the branch line,) but they were necessarily discontinued at the Port Neuf, from the 
breakage of the barometer with which they had been conducted. Near that point connexion 
is made with the observations taken by Fremont, which extend to Missouri river. I have 
already referred to the mere relative value of the barometric profile, as furnishing a lineal 
section with which side examinations can be connected. I am indebted to the patriotism of Dr. 
John Evans, geologist of Oregon and Washington Territories, for the furnishing of the instru¬ 
ment to which I allude, which, at the time of my departure, was the only barometer to be 
procured on the northwest coast, 
I am also under obligations to the same able and scientific explorer for reliable information 
of the great valley of Snake river, north of the Blue Mountain range—information which proved 
of great service to me in expediting the progress of the reconnaissance. 
