This is a WONDERFUL Theodolite made by Michel Cadot and dated 1740.

The fish on the side of the Theodolite represent Dauphins (Dolphins in English). The Dauphin of France was the title given to the heir apparent to the King of France. Putting a Dauphin on an instrument was a nod to the future King of France. I've seen a handful or two on instruments with Dauphins like this, and each one of those instruments was wonderful as well.

This Theodolite can measure angles to 10 minutes of a degree with the transversal/concentric circle arrangement. The Theodolite can function as a Surveyor's Cross with the four fixed sight vanes each separated by 90 degrees. The Theodolite can also function as a Circumferentor/Surveyor's Compass since the compass turns with the Alidade, making it possible to measure with the magnetic needle alone.

An instrument with transversals - the concentric circles - adds a lot of eye-appeal and interest to early instruments in my opinion. In theory a surveyor could read angles to ten minutes of a degree with this Cadot Theodolite. As Norwood pointed out at page 80 et seq. in his 1639 book on Fortifications, the mathematics behind the concentric circles and diagonals approach were fairly complicated, with many makers likely missing the mark. Over time most makers opted to use a vernier system instead of the concentric circle and diagonals system. Again, this makes for a really neat story if you display this Cadot Theodolite.

Michel Cadot apprenticed to the famous instrument maker Delure in 1718 in the Founders' Company. Cadot was the son-in-law of, and successor to, Henry Macquart (who was a well-known maker of instruments as well circa 1700). My Cadot Theodolite is signed "Cadot Gendre de Macquart Paris 1740". "Gendre de Maquart" means son in law of Maquart.

Please take a look at my 360 Degree View of the Cadot Theodolite (immediately below). You can Zoom in on any angle, so you can really see just how special this Theodolite is.

If you are interested in a bit more information about Michel Cadot and the instruments he made, please see my Michel Cadot Maker Webpage.

Finally, if you are interested in learning more about Theodolites made from 1500 to 1800, please see my Theodolites (1500 to 1800) Webpage. The Cadot is what I call a Second Generation Theodolite, so go directly to that page if you want to learn more about Theodolites made at roughly the same time as the Cadot Theodolite.