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GeographyMapping Unknown Lands
Those Cryptic Journal Entries
Declination
 

Surveyor Compass

Use cursor to rotate and open compass cover.

his instrument was normally mounted on the end of a staff that could be rested on the ground. The compass housing and the cross piece with the vertical metal "sights" on either end rotate. To take a bearing, Lewis or Clark would rotate the cross piece and upright sights while looking through the holes for a fixed visible point. When that fixed point was found, the bearing or azimuth between it and the observer could be read from the compass dial.

--John Logan Allen

Those Cryptic Journal Entries
Declination


 
From Discovering Lewis & Clark ®, http://www.lewis-clark.org © 1998-2014
by The Lewis and Clark Fort Mandan Foundation, Washburn, North Dakota.
Journal excerpts are from The Journals of the Lewis and Clark Expedition, edited by Gary E. Moulton
13 vols. (Lincoln: University of Nebraska Press, 1983-2001)