Restoration of a 17th Century Alta-Azimuth Theodolite

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 an important historical, as well as scientific, instrument.

The maker’s name, Joseph Hone was mentioned in Gloria Clifton’s book1 and J. R. Millburn’s article, Some English Military Instrument Makers of the 17th Century. In Millburn’s article he noted, “The principal supplier of ‘mathematical’ instruments to the Government during the reigns of James II, William & Mary, and William III, seems to have been the relatively unknown Joseph Hone.” He continues, “No surviving signed examples of his products have been reported, so his abilities as an instrument maker – if indeed he was an actual maker – cannot be assessed.”

Gloria Clifton confirmed that John Rowley began his apprenticeship to Hone on 23 November 1682. Rowley became an important instrument maker and also a supplier of instruments to the Board of Ordnance, as well as Christ’s Hospital, as was Joseph Hone. The signed theodolite serves as proof that Hone was a maker of exceptional quality, evidenced not only by the superior workmanship of the instrument but additionally by the very accurately engraved divisions on the theodolite’s azimuth circle.

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