Beautiful Simple Theodolite Made by Howard Circa 1740

Early Theodolites are very cool instruments - they were a very meaningful step above the surveyor compasses made and used in Colonial and Early America.

Given America's vast amount of heavily forested and uncultivated lands, the magnetic compass was the tool of choice for most of the surveys that happened in Colonial America. But there is evidence aplenty that Theodolites played a role in surveying Colonial America.

Collecting these early theodolites is a bit tricky. Only a handful were made in Colonial or Early America, and they command a huge premium if you are lucky enough to find one for sale. A fair number of early theodolites were likely imported into America, but it is usually impossible to know if any given instrument was used to survey in Early America or was imported into the country much later by an American collector. Interestingly, I didn't come across very many early theodolites either in the U.S. or UK during my research - I expected to find more.

NOMENCLATURE

Theodolite (aka Theodolet) - Prior to 1725, a full circle divided by degrees, usually with 4 sights. 2 sights were fixed at North and South, and 2 sights were movable. Could measure angles independently of the Needle. Most often but not always seen with a magnetic needle compass in the center. I refer to these as Second Generation Theodolites in my Ancient Surveying Instrument Section.

Improved Theodolite - Developed around 1725 with an illustration contained in Wyld's 1725 book on Surveying. Called an Improved Theodolite in Hammonds 1731 book on Surveying, which featured a neat illustration as well. An Improved Theodolite could measure vertical angles as well as horizontal, and featured a telescope. From 1725 until the early 1800's, these theodolites were often called an Improved Theodolite or a Telescopic Theodolite (or some version of that). After the Improved Theodolite dominated the market, sometime around 1800 or so these instruments became known as just "Theodolites". Later on, they would sometimes be called "Altazimuth Theodolites" by Museums and collectors. See the 1982 Whipple Museum Catalogue (Catalogue Cover) for the a really good explanation of the term "Improved Theodolite". I refer to these as Third Generation or Altazimuth Theodolites in my Ancient Surveying Instrument Section.

Simple, Plain or Common Theodolite - After the Improved Theodolite was developed around 1725, the non-Telescopic 2 and 4 vaned Theodolites were referred to as a "Theodolite" or a Simple or Common Theodolite. I think I've seen it referred to as a Plain Theodolite as well. Unfortunately, many collectors and auction houses now call these 2 and 4 vaned non-telescopic instruments "Circumferentors". "Circumferentors" was an early term used to refer to a surveyors compass. See the 1982 Whipple Museum Catalogue (Catalogue Cover) for a really good explanation of the term "Simple Theodolite".

Theodolite is the what colonials and early Americans called the 2 and 4 vaned instruments. So if you are researching these instruments in old books and newspapers, you search for "Theodolite". If you are looking for current auctions for these instruments, "Circumferentors" will generate the most hits.

For the sake of clarity, I'm calling the 2 and 4 vaned non-telescopic Theodolites here "Simple Theodolites".