MadSci Network: Science History |
Apparently Lewis and Clark had no method of measuring their actual altitude above sea level during their expedition. At the time of their journey, the only way of determining the altitude at a particular location with an instrument was by measuring the barometric pressure at that location. The aneroid barometer was not developed until the middle of the 1800s, so they would have needed a mercury barometer, which would have been very fragile and awkward. There is no record in their list of scientific equipment procured for the journey of a mercury barometer. The only other method available would have been to use a transit or quadrant to survey and compute the change of elevation staring from a point of known altitude and continuing by line of sight from point to point, measuring the angle and distance between each, to their location. This would have been impossibly difficult and time consuming. Lewis and Clark did have a transit for celestial measurements to determine latitude and longitude, and possibly used it to estimate the height of landmarks, but this would have the height above the location of the transit, not sea level, and would also have required knowing the distance to the landmark. References: A description of altitude determination by explorers in the 1840s. http://hometown.aol.com/rte395/hypsometry.html Equipment and supplies taken on the Lewis and Clark expedition. http://www.senate.gov/~dorgan/lewis_and_clark/supplies.html
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