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FROM THE DALE BEEKS COLLECTION

This is a beautiful 1824 Elijah Whiton Semi-Circumferentor - made in Groton Massachusetts. This Semi-Circumferentor includes a rarely encountered transversal scale, which allowed surveyors to read a single degree in 10 minute incredments. This wonderful instrument comes with its original box, drafting tools, a staff adapter and a really cool lock for the box. The instrument, box and accompanying pieces makes for an incredible display set. This Semi-Circumferentor checks all of the boxes when it comes to collecting - American made, rarely encountered, interesting features, great condition, and complete. Very obvious to me why Dale would add this special instrument to his personal collection.

This Semi is Serial Number 4. I know of 3 other Whiton Semi-Circumferentors and a couple of Whiton Compasses. I believe the highest serial number that I've seen so far is in the low to mid 30's. At Serial Number 4 this is the oldest Whiton instrument that I know about.

While the Semi indicates it is a Patent design, Whiton apparently never received a patent for this style of instrument. Dale also owned Whiton Semi-Circumferentor Serial Number 11, and that instrument does not have a Patent designation.

Dale has a file related to this instrument, and a pic showing some of the file (including Dale's handwritten notes) is attached below. Dale's note contains the specs for the instrument - the Semi is a bit more that 15 inches wide as measured from fixed sight vane to fixed sight vane.

This Semi has offered several advantages over a traditional vernier compass. First, it can measure horizontal angles independently of the needle. Second, it is setup to measure vertical angles as well. And Third, a surveyor could quickly break a degree into 10 minute increments with the transversal scale.

I suspect that Whiton had really bad timing when he designed this wonderful instrument. Just a few years later William Young would develop his Improved Compass - what the NY makers called a Railroad Compass, which was a traditional surveyors compass that could also measure angles independently of the needle.

One last point is worth mentioning. Note the sight vanes on the fixed blade. The fixed sight vanes have a strip of brass that folds down to be perpendicular to the sight vane. I don't know the function of those brass strips. The fixed sight vanes are not interchangeable. So the flip down brass strips points in the direction of the main part of the instrument on both sides. If you know the function of those brass strips please shoot me a note. Thanks!

Please see my Elijah Whiton Maker Webpage for more information about Whiton.