Great Plains Studies, Center for
Date of this Version
Winter 1984
Citation
Great Plains Quarterly Vol. 4, No. 1, Winter 1984, pp. 54-69.
Abstract
The Lewis and Clark expedition, "the most consequential and romantic peace-time achievement in American history," had its genesis in the mind of Thomas Jefferson fully two decades before the exploring party departed from Pittsburgh on 31 August 1803. The need to determine the character and . expanse of the western regions of the continent lingered in his mind, and during the intervening years he encouraged three unsuccessful attempts to explore them. After he assumed the presidency in 1801, he was finally able to bring his dream to realization. The venture not only achieved all that Jefferson had hoped, but also was the first and one of the most important applications of scientific practices and instrumentation attempted by the young republic.
The third president was eminently suited to plan such a project, for he was better informed on national geography than anyone else in the United States. He had spent many years collecting and studying all that had been written and published about the subject, and he had had ample opportunity to meet Indians and others who had traveled in the West and to record all that he could learn from them. He was knowledgeable about scientific practices and instruments and was experienced in surveying, mapping, and making astronomical observations, all of which would be required to record the regions to be explored. As president of the American Philosophical Society, Jefferson could call upon the nation's most eminent men of science for advice on all the subjects that would concern the proposed expedition.
Selecting his own secretary, Meriwether Lewis, to lead the exploring party, Jefferson set him the task of compiling lists of the needs and estimates of costs of such an undertaking, even before the president submitted the proposal to Congress. Lewis would prove an excellent leader: he was self-taught in the natural sciences, a lover of the outdoors, and, as a former army officer, experienced in the handling of men. He was also familiar with the lands beyond the Allegheny Mountains.
Jefferson made his own instruments and scientific library available to Lewis and personally instructed him in the use of the instruments required for surveying and determining latitude. Lewis practiced particularly with the octant (fig. 1), an instrument designed primarily for use at sea but used also on land to observe altitudes of the sun or a star for determining latitude.
Triangular in shape, the instrument was made of a closely grained tropical wood, the limbs blackened to eliminate glare. Ebony was preferred and most often used because it was already black. A movable arm or index pivoted from the apex. About 1750,. brass replaced wood for the index arm. Two sets of colored glass shades were provided for use with the sun, and a sight (or later, a telescope) was attached to the right limb. Early octants had a second sight on the opposite limb, to be used when the horizon below the sun was poorly defined and the opposite horizon had to be used. A mirror fixed to the apex moved with the arm. A glass, half mirrored and half clear, was situated on the left limb, opposite the sight.
Comments
Copyright 1984 by the Center for Great Plains Studies, University of Nebraska-Lincoln