Navigation for Lewis and Clark: Theodolite

This photo is of one of Mr. Jefferson’s theodolites and is on display in his study at Monticello.

Photo: Thomas Jefferson Foundation

As they set off on their epic journey of many purposes, Captains Lewis and Clark took along a wide array of mathematical instruments to help them chart and survey the nation’s land acquisition. This set of sophisticated tools included a theodolite – used to measure vertical and horizontal angles.

There was much debate about bringing along a theodolite, as some felt such an instrument was too delicate for the long, arduous journey. Both Lewis and Thomas Jefferson, however, believed it was essential, and the president (who knew all about surveying) offered to lend his personal theodolite.

Mr. Jefferson’s theodolite was created by Jesse Ramsden, a famous British instrument maker, also known as the developer of the “Great Theodolite,” a massive instrument that could accurately measure over a distance of 70 miles.

Source: “The Scientific Instruments of the Lewis and Clark Expedition,” by Silvio A. Bedini, Smithsonian Institution