4639. LEWIS AND CLARK EXPEDITION, Preparations.—
I had long deemed it
incumbent on the authorities of our country to
have the great western wilderness beyond the
Mississippi explored, to make known its geography,
its natural productions, its general character
and inhabitants. Two attempts which I
had myself made formerly, before the country
was ours, the one from west to east, the other
from east to west, had both proved abortive.
When called to the administration of the general
government, I made this an object of early
attention, and proposed it to Congress. They
voted a sum of five thousand dollars for its
execution, and I placed Captain Lewis at the
head of the enterprise. No man within the
range of my acquaintance united so many of
the qualifications necessary for its successful
direction. But he had not received such an
astronomical education as might enable him to
give us the geography of the country with the
precision desired. The Missouri and Columbia,
which were to constitute the tract of his journey,
were rivers which varied little in their
progressive latitudes, but changed their longitudes
rapidly and at every step. To qualify him
for making these observations, so important to
the value of the enterprise, I encouraged him
to apply himself to this particular object, and
gave him letters to Doctor Patterson and Mr.
Ellicott, requesting them to instruct him in the
necessary processes. Those for the longitude
would, of course, be founded on the lunar distances.
But as these require essentially the aid
of a time-keeper, it occurred to me that during
a journey of two, three, or four years, exposed
to so many accidents as himself and the instrument
would be, we might expect with certainty
that it would become deranged, and in a desert
country where it could not be repaired. I
thought it then highly important that some
means of observation should be furnished him
which should be practicable and competent to
ascertain his longitudes in that event. The equatorial
occurred to myself as the most promising
substitute. I observed only that Ramsden, in his
explanation of its uses, and particularly that of
finding the longitude at land, still required his
observer to have the aid of a time-keeper. But
this cannot be necessary, for the margin of the
equatorial circle of this instrument being
divided into time by hours, minutes and seconds,
supplies the main functions of the time-keeper,
and for measuring merely the interval
of the observations, is such as not to be neglected.
A portable pendulum for counting, by
an assistant, would fully answer that purpose.
I suggested my fears to several of our best
astronomical friends, and my wishes that other
processes should be furnished him, if any could
be, which might guard us ultimately from disappointment.
Several other methods were proposed,
but all requiring the use of a time-keeper.
That of the equatorial being recommended by
none, and other duties refusing me time for
protracted consultations, I relinquished the idea
for that occasion. But if a sound one, it should
not be neglected. Those deserts are yet to be
explored, and their geography given to the
world and ourselves with a correctness worthy
of the science of the age. The acquisition of
the country before Captain Lewis's departure
facilitated our enterprise, but his time-keeper
failed early in his journey. His dependence,
then, was on the compass and log-line, with the
correction of latitudes only; and the longitudes
of the different points of the Missouri, of the
Stony Mountains, the Columbia and Pacific, at
its mouth, remain yet to be obtained by future
enterprise.—
To——. Washington ed. vii, 224.
(M.
1821)
See Latitude and Longitude.
