Victorian Borda Type Reflecting Circle by Thomas Wegener of Berlin

For sale, a late Victorian Borda type Reflecting Circle by Thomas Wegener of Berlin.

Complete with its original sighting telescope, magnifier with light diffuser on pivot arm for reading at every point of the circumference and an unusual glass prism and mirror combination. The scale is divided and numbered to three hundred degrees but is further divided around the majority of the circumference to allow for a second reading to be taken from the single limb with a Vernier to each end. The ability for a dual reading vastly improved the accuracy of the instrument.

The instrument is ten inches in diameter and has double handle to the reverse.

The limb is superbly engraved to the German maker, “Th Wegener Berlin, No: 331” and is the earliest of any known example of these instruments from his workshop.

The reflecting circle was invented by the German astronomer, Tobias Mayer in 1752 and was submitted to The Board of Longitude for use in sea trials. Admiral John Campbell the developer of the sextant was known to have constructed an example from Mayer’s plans but it was considered too heavy and cumbersome to be of practical use.

Perhaps due to the involvement of Campbell in these trials and of course with his own invention of the sextant coming in 1757 it is unsurprising that the latter became more widely used in the United Kingdom. Towards the end of the Eighteenth Century, Edward Troughton produced a refined version of the instrument but the sextant continued to be preferred by British Mariners throughout the Nineteenth Century.

Towards the end of the Eighteenth Century, the French Mathematician and Sailor, Jean-Charles de Borda was more successful in popularising the reflecting circle on the Continent and the instrument was widely used throughout. His work on Mayer’s initial ideas and the manufacturing skills of the instrument maker, Etienne Lenoir, resulted in the instrument becoming less cumbersome and eventually became more commonly known as the Borda Circle.

There is little to be found on the company of Thomas Wegener but it is likely that he traded in Berlin during the latter half of the Nineteenth Century. It is certain that Wegener’s business was more than a domestic concern as a later reflecting circle with serial 1773 is engraved as being imported to the US by CL Berger & Sons of Boston at the end of the century (the company formed in 1898). Berger had roots in Stuttgart so it is perhaps unsurprising that trading links were established there. Other clients included the Dutch Navy who bought sextants from Wegener.

Circa 1880