Brass Theodolite 10"

Used for surveying and reading lines of sight and angles, the theodolite utilizes a telescope mounted on two movable planes, one horizontal and one vertical. Very similar to the navigational sextant, the theodolite is a more advanced device in that it is capable of measuring both the horizontal and vertical planes simultaneously. While the antique sextant can only measure one plane at a time, it has an advantage at sea in that it does not have to be leveled. Mounted on a tripod, the theodolite must be leveled in order to obtain accurate readings. Though the brass sextant and the theodolite operate on the same basic principle, because of their differences the theodolite is more effective on land while the brass sextant operates better at sea. A common tool since the late 18^th century, the theodolite had its inception prior to 1512, with the invention of the polimetrum. The first written account of the term “theodolite” was by published in 1571, though the modern instrument was not developed until the 1700s, when the ability to mass produce these tools came about in manufacturing. As with the brass sextant, both British and American navies and sailors used the theodolite in continuing to make accurate maps of both the sea and undiscovered land.