On the first of each month, I typically offer one or two special surveying instruments for sale as my Instruments of the Month. For December 2023, I’m offering two pretty special instruments - both were based on US Patents and made in Virginia prior to the Civil War. Both instruments were designed to take bearings based on the magnetic needle, or to measure angles independently of the needle. And both were designed to measure either horizontal or vertical angles.
Prior to the Civil War, there were very few surveying instruments that were subject to a U.S. Patent. And there were very few surveying instruments made by Southern makers.
The oldest instrument (made in 1837 or so) is the Whiteley Quadrant. The other instrument is the Danner Trigonometer.
For background information about these types of instruments, and to see the patents involved, please see my Collecting Whiteley - Danner - Whitescarver Quadrants - Trigonometers Webpages.
Thanks,
Russ