About 12 years ago I was fortunate to obtain a 17th century English theodolite complete with its original, octagonal box and Jacob’s staff adaptor. At the time of acquisition I was not familiar with the names engraved on the arms of the azimuth plate. Once I began to research the names, I realized this was […]

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After having completed several restorations on instruments owned by the American Philosophical Society, I was appointed to the Committee on Museum to review the condition of current instruments in its collection and to contribute to the vetting process of new acquisitions. After the 2015 American Philosophical Society Committee on Museum meeting, Chairman Keith Thomson brought […]

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Charles Mason and Jeremiah Dixon arrived in Philadelphia on November 15, 1763. Over the next five years they established locations and boundaries to seconds-of-arc accuracy, a remarkable feat in the Old World and unprecedented in the New. They brought with them two major instruments, both crafted by London’s John Bird, the foremost instrument maker of […]

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Jeffery Lock of Colonial Instruments detail the fabrication of the telescope cradle and tripod John-Bird-Transit-Telescope

A Masterpiece of Colonial Technology

As a researcher and restorer of 18th century Colonial surveying instruments, I primarily deal with the artistically crafted surveying compass. These instruments often have beautifully executed engraving, combined with technologically advanced workmanship for their generation. They stand out from the later instruments of the mid-19th century where mechanical repetition produced functional instruments devoid of the spark of artistic creativity.

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An instrument by Thomas Greenough (working in Boston: 1730 – 1785) has surfaced possibly having dual functionality as a theodolite and circumferentor. When this instrument was found, its sight vanes were missing. This Greenough instrument was designed for four sight vanes – two fixed and two moveable.

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Published in American Surveyor Magazine

In the American colonies during the 18th century, the construction of the surveyor’s compass ranged from crude to sophisticated. Most New England instruments from this period were made primarily of wood and had printed papaer cards for the divisions of the degrees. This article does not address the wooden compasses with engraved paper cards, but rather the means by which the colonial instrument manufacturers divided the needle rings for their manufactured surveying compasses prior to the introduction of a Jess Ramsden-inspired dividing engine.

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When I first laid my eyes on the Lewis Michael compass, words could not describe the emotions I felt. I was looking at one of the most beautifully engraved examples of the 18th century Colonial instrument maker’s art. I have been collecting Colonial antiques for decades and had never seen an example of craftsmanship that […]

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One of the enjoyments of performing restorations on early surveying instruments is when the owner has no idea that he is in possession of an extremely rare and/or important historical compass and you have the opportunity to contact them with a pleasant surprise regarding their instrument. One such instrument was uncovered recently after Colonial Instruments […]

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