Entrance to the exhibit, The Mapmaker's Eye: David Thompson on the Columbia Plateau.1
The map shown above is a full-size reproduction (c. 96 x 84 inches) of David Thompson's chart of the region then known as the Oregon Territory.
The Proper Instruments
David Thompson was born to Welsh parents in the village of Westminster, just on the edge of London, in April of 1770—exactly the same year that William Clark was born in Virginia, and only four years before Meriwether Lewis. Although Thompson's father died when he was one and little is known of his mother, the boy received a solid mathematical education at the Gray Coat Hospital, a charity school on the grounds of Westminster Cathedral. In May of 1784, David Thompson, aged fourteen, sailed across the Atlantic to begin a seven-year clerk's apprenticeship with the Hudson's Bay Company, initiating a long career of trade and exploration that would eventually carry him to the mouth of the Columbia River.
Gardening was one of several practical skills young David Thompson learned at the Gray Coat School in Westminster, which he attended during the time of the American Revolution. In spring 1809, when he arrived at the Tobacco Plains of the Kootenai tribe in northwest Montana, he took advantage of his training and the favorable soil to plant seeds of barley, turnips, and English peas.
During that same month of May, 1784, Thomas Jefferson was traveling the opposite way across the same ocean, assigned to join U.S. envoys Benjamin Franklin and John Adams in Paris. While Jefferson negotiated his way through different strata of Enlightenment society and succeeded Franklin as ambassador to France in 1785, young David Thompson learned the basic skills of the Canadian fur trade, including accounting, wilderness survival, practical natural history, and how to pay attention to local tribal knowledge in order to stay alive. While Jefferson improved his French, Thompson picked up Cree, which as a trade language extended clear across the Prairies to the Rocky Mountains.
Separated by age, an ocean, and the most different social positions imaginable, the two men nonetheless shared a keen interest in astronomy, which at that time included the discipline of practical surveying. Upon Thompson's graduation, the Gray Coat school had presented him with a fine Hadley's quadrant and a copy of the Nautical Almanac—the Hudson's Bay Company hoped that the boy would become not only a clerk in the fur business, but also a surveyor who could codify routes through their business empire. Thompson showed enthusiasm for the goal, and at the end of his apprenticeship requested that the company supply him with scientific instruments rather than the standard new suit of clothes.
In time he collected a good Dollond sextant, a four-foot Dollond achromatic telescope with three different lenses, two accurate chronometers, and a full kit of drawing instruments that would enable him to make precise maps.
Thomas Jefferson followed a similar path. When he traveled to London on diplomatic business in the spring of 1786, one of his first side trips was to the shop of instrument maker Peter Dollond. There he purchased a telescope and other scientific instruments.2 Peter Dollond's father John had patented the first achromatic lens for telescopes, which eliminated the blur of color refraction. These lenses allowed astronomers to make crisp shots on the edges of heavenly objects. Surveyors such as David Thompson used such shots in conjunction with astronomical tables to accurately set their timepieces—a crucial beginning to the determination of a correct longitude. Among the instruments Thomas Jefferson used at Monticello was a four-foot Dollond telescope with three achromatic lenses and a collapsible pot-metal tripod, which fit snugly in an oblong wooden case. In his writings, David Thompson describes using exactly the same instrument to make his observations in the Saskatchewan, Athabasca, Peace, and Columbia River drainages.
1. Jack Nisbet's book of the same name was written to enhance the exhibit erected by the Northwest Museum of Arts & Culture. For information on Mr. Nisbet's other publications, see his biographical note.
2. Silvio A. Bedini, Thomas Jefferson: Statesman of Science (New York: Macmillan, 1990), 151.
Funded in part by a grant from the National Park Service, Challenge-Cost Share Program