Artificial Horizon--Water
n July 22, 1804, while at White Catfish Camp on the Missouri River, ten miles above the mouth of the Platte, Lewis devoted most of journal entry to a description of each of the instruments he and Clark used in making celestial observations. The first type, illustrated here in a drawing by Robert N. Bergantino, was the simplest.
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n Artificial Horizon on the construction recommended and practiced by Mr. Andrw. Ellicott of Lancaster, Pensyla., in which water is used as the reflecting surface; believing this artificial Horizon liable to less error than any other in my possession, I have uniformly used it when the object observed was sufficiently bright to reflect a distinct immage; but as much light is lost by reflection from water I found it inconvenient in most cases to take the altitude of the moon with this horizon, and that of a star impracticable with any degree of accuracy."This page is supported in part by a grant from the National Park Service CCSP Program.
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