sperit-level

Updated: June 25, 2025

Patterson of Philadelphia; glass is here used as the reflecting surface. this horizon consists of a glass plane with a single reflecting surface, cemented to the flat side of the larger segment of a wooden ball; adjusted by means of a sperit-level and a triangular stand with a triangular mortice cut through it's center sufficiently large to admit of the wooden ball partially; the stand rests on three screws inserted near it's angles, which serve as feet for it to rest on while they assist also in the adjustment. this horizon I have employed in taking the altitude of the sun when his image he has been reather too dull for a perfect reflection from water; I have used it generally in taking the altitude of the moon, and in some cases of the stars also; it gives the moon's image very perfectly, and when carefully adjusted I consider it as liable to but little error.

William Clark - The Journals of Lewis and Clark, 1804-1806