David Thompson
Jefferys, Charles W. 1945
The Picture Gallery of Canadian History Vol. II, p.146
David Thompson
Library and Archives Canada, Acc. No. 1972-26-1406
Remarks
Thompson is using an artificial horizon. This is a flat iron pan into which mercury was poured. The pan is covered by a sloping glass roof, and placed on perfectly level and firm ground or rock in a situation to reflect the image of the sun. The surveyor looks through the eye-piece of his sextant at this reflected image, and finds the angle which gives the elevation of the sun at its meridian above the horizon. From this he is abie to calculate his position.
Notice in the illustration the iron bottle in which the mercury is carried, the note-book and pencil, and the camp in the middle distance, far enough from the observer to prevent any disturbance of the surface of the mercury by the tread of horses or men. The length of the shadows and the distance of the artificial horizon from the observer show that the observation is being taken in autumn. For detailed information on early methods of surveying I am indebted to Dr. J. B. Tyrrell, of Toronto.
Publication References
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Paterson, Gilbert. (1933) Canada From the Earliest Times to the Present. p. 51
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Paterson, Gilbert. The Story of Britain and Canada. Toronto, Ryerson, 1933. 233 p. Illus. In 2 parts, with their own pagination. p. 51 - “David Thompson”
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Paterson, Gilbert. The story of our people. Toronto, Ryerson, 1933, 1938. 429 p. Illus. p.101 - “David Thompson”
- Stothers, J.C., Armitage, Elva and Kingston, Verda M. (1938) West by South Grade VI
- Jefferys, Charles W. (1945) The Picture Gallery of Canadian History Vol 2, p.146
- Wallace, W. Stewart, (1953) By Star and Compass
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Cole, A.O.C. “His map the only monument to David Thompson, Canada’s greatest geographer.” In Globe and Mail, Feb. 9, 1957, p. 23. Illus. “David Thompson uses crude artificial horizon…”
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Bowman, Bob. Dateline: Canada. Toronto, Holt, Rinehart and Winston, 1973. n.p. Illus. July 15 - “David Thompson taking an observation”
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Hardwick, Francis C., ed. The helping hand: the debt of Alexander Mackenzie and Simon Fraser to Indian Canadians. Vancouver, Tantalus Research Ltd., 1973. 78 p. Illus. p.13 - “Finding the sun’s elevation above the horizon by the use of the cross-staff” [David Thompson]
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Raymont, David. “How CP pioneered transpacific trade, travel.” In Canadian Geographic, Feb./Mar. 1980, p. 34-39. Illus. P.36 - “David Thompson (1770-1857) taking an observation with a sextant, as imagined by the artist, C.W. Jefferys.”
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Van Tighem, Kevin. Heritage rivers: preserving the spirit of Canada. In Canadian Geographic, Apr/May 1990, p. 50-59. Illus. p.56 - [David Thompson]
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Brown, Stephen R. “In the footsteps of David Thompson.” In Beaver, June/July 2002, p. 13-19. Illus. p. 18 - [David Thompson]
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Jenish, D’Arcy. Epic wanderer: David Thompson and the mapping of the Canadian west. Lincoln, U of Nebraska Press, 2003. 309 p. Illus. p. 68 - “Thompson observing with the sextant”
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Jenish, D’Arcy. “Exploring David Thompson.” In Legion Magazine, July 1, 2007. 4 p. illus.
www.legionmagazine.com/en/index.php/2007/07/exploring-david-thompson/ -
Donovan, Patrick. “The humbler Celts: in praise of the Welsh, whose impressive Quebec legacy belies their obscurity.” In Quebec Heritage News, Sept.-Oct. 2008, p. 10-11. Illus. p. 11 - “David Thompson Taking an Observation”
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