Exploration of the Red River of Louisiana, in the year 1852 / by Randolph B. Marcy ; assisted by George B. McClellan. Page: 3 of 368

INTRODUCTION.

In submitting the following report of a reconnoissance of the
country bordering upon upper Red river, it is proper to state
that, previous to our departure upon the expedition, we were
unable to procure all the instruments adapted to the performance
of such services as were required of us. We succeeded
in obtaining a sextant, a mountain barometer, an aneroid barometer,
an odometer, a prismatic compass, and two Fahrenheit
thermometers; but could not procure a chronometer,
and, in consequence, were under the necessity of making our
observations with a pocket lever watch.
The latitudes given are the results of from twelve to fifteen
observations of Polaris for the determination of each position.
The longitudes were determined by a series of observations
upon lunar distances, and are believed to be as accurate as
the imperfect character of our instruments would admit.
The positions thus deduced have been corrected by frequent
and careful observations of courses and distances with the
compass and odometer, a record of which will be found in
the appendix.
The astronomical observations were made by Captain
George B. McClellan, of the engineer corps, who, in addition
to the duties properly pertaining to his department, performed
those of quartermaster and commissary to the command. An
interesting collection of reptiles and other specimens, in alcohol.
was also made under his superintendence, and put into
the hands of Professors Baird and Girard, of the Smithsonian
Institution, whose reports will be found in the appendix. For
these and many other important services, as well as for his
prompt and efficient co-operation in whatever was necessary
for the successful accomplishment of the design of the expedition,
I take this opportunity of tendering my warmest acknowledgment.