Unsigned Colonial Semi Circumferentor – Owned by Silvio Bedini

Unsigned Colonial Semi Circumferentor – Owned by Silvio Bedini



Circa 1780

Country of manufacture

North America

Categories: Surveying Instruments & Mining, Engineering antiques


This unsigned colonial semi circumferentor was featured in the 1964 Bedini book (PDF) at Figure 34 and the accompanying text.   As indicated in the book, Bedini owned this instrument, and I came across a number of pics of the instrument while I reviewed Bedini’s files at the Smithsonian.  I included a front and back scans of one oft he Smithsonian photos below.


In his book, Bedini describes his semi circumferentor:


“Of equal interest is a large semicircumferentor made by an unknown American instrument maker in the second half of the 18th century. The instrument (fig. 34) consists of a plate of hammered brass attached to a quarter circle block of mahogany, with a glass covered trough compass within a silvered opening, and the gradations stamped into the brass. The brass sighting bars are attached to a swivelling bar that can be fixed in place with a set screw underneath the block. The instrument, which is in the collection of the writer, is not signed with a maker’s name. Its workmanship is excellent, and professional.”


The Semi Circumferentor lacked sight vanes and thumbscrews when owned by Bedini.  A subsequent owner had Jeff Lock make replacement vanes and thumbscrews – Jeff did a wonderful job.


Here are the specs:


14 inch alidade


8.5 inch needle


Inner scale to 1/2 degrees


This is a great opportunity to own Bedini’s colonial semi circumferentor.


You can also see a 360 degree view with a high resolution ZOOM feature of the this Colonial Semi-Circumferentor by clicking here.

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US The Compleat Surveyor

The Compleat Surveyor specializes in rare instruments and books related to land surveying. This initially was a family business - my father (F. D. Uzes) was a noted surveyor, collector and author (Illustrated Price Guide To Antique Surveying Instruments and Books - published in 1980). Having spent a lifetime surrounded by old instruments and books, I now run the business myself. I use my website (www.CompleatSurveyor.com) to both sell instruments and provide historical information related to land surveying.

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