CHAPTHLR It. 
Field Explored by Different Parties. 
As the field contemplated in my instructions extended from the great lakes to the Pacific 
coast, and from the 49th parallel to the emigrant route of the South Pass, and as no portion 
of this field had been explored since the days of Lewis and Clark, except a small portion 
towards the Pacific coast; as a portion of it was occupied by Indians supposed to be treacherous 
and hostile, and as it was in a high latitude, much abridging the season of active operations, 
it was determined that the exploration should be conducted in two divisions, operating respect- 
ively from the Mississippi river and Puget sound; and that a depot of provisions should be 
established by a third party at the St. Mary’s village, at the western base of the Rocky 
mountains, to facilitate the winter operations of the exploration, and enable the exploring parties 
to continue in the field the longest practicable period; and that all the parties should be organ- 
ized in a military manner for self-protection, and to force their way through whatever diffi- 
culties might be encountered. 
Accordingly, Captain George B. McClellan, corps of engineers, was assigned to the charge of 
the western division; Lieut. Rufus Saxton, jr., to the duty of establishing a depot in the St. 
Mary’s valley; and the eastern division was under my own personal direction. A small military 
force was assigned to each, and the necessary scientific corps, composed of officers of the 
army and civilians. 
The western division was charged with the duty of exploring the passes of the Cascade 
mountains, from the Columbia river to the northern parallel, and of pushing eastward to meet 
the eastern division between the Cascade and Rocky mountains. Captain McClellan was assisted 
in this duty by Second Lieut. Johnson K. Duncan, third artillery, astronomer, topographer, 
and artist; Second Lieut. 8. Mowry, third artillery, in charge of the meteorological operations; 
Second Lieut. H. C. Hodges, fourth infantry, quartermaster and commissary; J. F. Minter, 
Esq., civil engineer; George Gibbs, Esq., geologist and ethnologist; Dr. J. G. Cooper, surgeon 
and naturalist; A. L. Lewis, Esq., civil engineer and interpreter. 
Lieut. Rufus Saxton, jr., in addition to establishing the depot at the western base of the 
Rocky mountains, was directed to make a reconnaissance of the country passed over by him, 
with the view of combining the operations of the eastern and western divisions; and he was 
assisted in this duty by Second Lieut. Richard Arnold, third artillery, assisted by Mr. Lyman 
Arnold, in charge of astronomical observations; Second Lieut. R. Macfeely, fourth infantry, in 
command of the escort; and D. 8. Hoyt, meteorologist and topographer. 
The eastern division, excluding the mention of certain officers and civilians who were on duty 
only for a short time, and whose cases have been brought to your notice in previous reports, con- 
sisted of Second Lieut. A. J. Donelson, corps of engineers, in command of a detachment of ten 
sappers and miners; Second Lieut. Cuvier Grover, fourth artillery ; Second Lieut. John Mul- 
lan, fourth artillery; Doctor George Suckley, surgeon and naturalist; Isaac F. Osgood, Esq., 
disbursing, quartermaster’s, and commissary agent; J. M. Stanley, artist; F. W. Lander and 
A. W. Tinkham, Esqs., civil engineers; John Lambert, Esq., topographer; George W. Stevens, 
Esq., astionomer, and for a portion of the route in charge of the magnetic observations, assisted 
by James Doty; William M. Graham, Esq., astronomer; Joseph Moffett, meteorologist; T. S. 
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