Lewis and Clark diaries provide directional clue.When Meriwether Lewis and William Clark set off to explore the Louisiana Territory Louisiana Territory was a historic, organized territory of the United States from July 4, 1805 until December 11, 1812. It consisted of the portion of the Louisiana Purchase that was not partitioned off into Orleans Territory, which later became the state of Louisiana. in 1804, President Thomas Jefferson directed them to note the location of interesting points along the way. The explorers diligently calculated latitude and longitude latitude and longitude Coordinate system by which the position or location of any place on the Earth's surface can be determined and described. Latitude is a measurement of location north or south of the Equator. and recorded compass bearings as they traversed the continent. But compasses have a major drawback for creating long-lasting maps. Instead of pointing to the geographic North geographic north The direction from any point on Earth toward the North Pole. Also called true north. Compare magnetic north. Pole, which is constant, they align with the magnetic north, which changes as molten iron moves within Earth's core. Lewis and Clark took sextant sextant, instrument for measuring the altitude of the sun or another celestial body; such measurements can then be used to determine the observer's geographical position or for other navigational, surveying, or astronomical applications. readings of the positions of the sun and North Star to be used with their compass measurements to calculate the difference between the geographic and magnetic poles. However, computation of this so-called magnetic declination declination, in astronomy, one of the coordinates in the equatorial coordinate system. The declination of a celestial body is its angular distance north or south of the celestial equator measured along its hour circle. was never completed. Nearly 200 years later, geologist Robert E. Criss of Washington University in St. Louis “Washington University” redirects here. For other uses, see Washington (disambiguation). Washington University in St. Louis is a private, coeducational, research university located in St. Louis, Missouri. has finished the job, and he's used the results to fine-tune the explorers' maps. By filling in gaps in the historical record, his findings also add to the understanding of Earth's interior magnet. "[Lewis and Clark] were stunningly good record keepers. They got more than enough data to make these determinations," says Criss, who reports his findings in the October GSA (1) (Global mobile Suppliers Association, Sawbridgeworth, U.K., www.gsacom.com) A membership organization of suppliers of GSM products and services. Its goal is to promote GSM as the worldwide mobile communications standard. See GSM Association and GSM. Today. Criss mined the explorers' expedition journals for records on the altitude and compass-determined direction of the sun and North Star. He then used tables to calculate the star's known location on given dates in the early 1800s and compared the two sets of locations to determine how far the magnetic pole was throwing the compass out of whack. Criss found that the magnetic pole was just less than 8[degrees] east of true north in St. Louis at the start of the explorers' journey but was around 20[degrees] east at Cape Disappointment, Wash., where the explorers turned around to head for home. The current declination in St. Louis is 0[degrees] and in Washington State, it's still around 20[degrees] east. Whereas ships' captains have recorded declinations over the oceans for the past 400 years, the U.S. interior was a blank until the second half of the 19th century. The new measurement provides the earliest midcontinent data. Scientists are still working out how Earth's core creates the planet's magnetic field. "We need to understand as well as we can the time and space changes in Earth's magnetic field Earth's magnetic field (and the surface magnetic field) is approximately a magnetic dipole, with one pole near the north pole (see Magnetic North Pole) and the other near the geographic south pole (see Magnetic South Pole). in order to figure out how the field operates; says Robert F. Butler of the University of Arizona (body, education) University of Arizona - The University was founded in 1885 as a Land Grant institution with a three-fold mission of teaching, research and public service. in Tucson. "Theories are only as good as the records of past variations." Criss also used the declinations to correct some of the explorers' maps. For example, he looked at one sketch of Big Bend, S.D., where Lewis and Clark took compass measurements and estimated distances between campsites. Once Criss rotated the map 12.5[degrees] counterclockwise to compensate for the magnetic declination at that time, the map proved remarkably similar to current maps, he says, a tribute to the explorers' careful observations. "With Lewis and Clark, there's an often-heard message of heroism," says Criss. "There's another message hidden here about what fine scientists they were." |
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