Scientific Instruments of the Lewis and Clark Expedition

By S tuart Wier

The most important “instruments” of the explorers were their writing  materials. They wrote with quill pens in small notebooks, about 5 by 8  inches, top hinged on the short end, bound in reddish-brown leather, or  bound in marbled paper with leather corners. They apparently took ink powder to make the ink, not bottles of ink. One evening Clark noted that York was making ink. Exploring on shore, each captain wrote notes and would have carried a “portable inkstand” a small brass case with a couple of short quills and a tiny bottle of ink. Lewis bought 100 quills in Philadelphia, and ink powder. He obtained “six brass inkstands” from army supplies, and purchased two “lanthorns” and 2 “lamps” for writing at night. The explorer's maps and records of discoveries in natural history and of Indian encounters were their great achievement. The surviving journals of the two captains, three sergeants and one private total over one million words. As Donald Jackson said, "they were the writingest explorers there ever were."

For celestial navigation Lewis obtained, in Philadelphia, “a brass Sextant of 10 Inches radius,” a “common Octant of 14 inches radius,” an “artificial horizon” (a reflecting surface, apparently a wooden tray for water with a glass cover), an artificial horizon consisting of a pane of glass cemented to a wooden ball and resting in a triangular stand of wood, another artificial horizon similar to the previous with an index mirror for a sextant in place of the pane of glass, and a chronometer of the “most improved construction” (its cost was $250; the most single expensive item on the expedition. This may be a small watch-sized chronometer, not the large naval kind). For mapping, using distances and directions, they employed a “Circumferentor,” a surveyor's compass with a 6 inch dial (such compasses have sighting vanes), a “spirit level,” a “Case of plotting instruments,” a “two pole Chain” (a surveyors chain 33.0 feet long to measure baselines), a “Silver plated pocket Compass,” a “Brass Boat Compass,” “three brass pocket compasses,” a magnet (to re-magnetize compass needles), a “Sett of slates in a Case” (to do calculations on, since paper was limited), and “log line, reel, and log ship.” A ship's log was intended for measuring ship speed on oceans. This was Jefferson's idea, but use of a log from boats on the turbulent western rivers was completely impractical and was never attempted, so far as we know. The ships log is not mentioned in the daily journals; perhaps it stayed home.

The large surveyor's compass was lost in a flash flood in a ravine near the great falls of the Missouri River in Montana, June 29, 1805. Clark sent men to try to find it in the muddy and rocky flood outwash debris the next day, and astonishingly, they did, in working order. Clark apparently brought his own personal pocket surveyor's compass, about 4 inches across with a wooden case. This is the single most important surviving piece of equipment remaining from the expedition. It is in the Smithsonian and in the National Bicentennial Exhibition. In addition the two captains had “spyglasses” - brass telescopes of 10 to 20 power, and three thermometers. Binoculars, wind speed gages, and aneroid barometers had not been invented.

Clark used his compass, and estimates of distance made by eye, to map the entire route to the Pacific. His final mileage estimate to the mouth of the Columbia was correct to within 1% in more than 4000 miles. Celestial navigation observations were made every few days on the journey – more than 200 times – but that data was never really used or published. The remarkable map of the western part of North America that Clark completed in 1810 became the single most valuable tangible result of the expedition and was a standard map of the west, used for decades.

All government equipment remaining after the expedition was sold at a public “dock sale” in St. Louis immediately after the expedition's return in September 1806. The purchase price for the material was a trifle more than $400. That is one reason so few articles remain from the journey of discovery. No surviving instruments are known except for Clark's compass.

For more books and resources, see online http://home.earthlink.net/~swier/CorpsofDiscovery.html

tuart Wier http://home.earthlink.net/~swier/LHSW.html

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Copyright © S tuart Wier 2005. All rights reserved. June, 2005

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