Invented by William Hyde Wollaston (1766-1828) in 1807, it was used to measure the angles between the plane surfaces of crystals or as a spectrometer to measure the dispersion of light through a prism.
Wollaston had the ingenious idea of using crystal faces as mirrors to measure the angles between them – a precursor to the modern diffractometer. A crystal remains mounted to this example.
The base is engraved with the maker’s address of 30 Strand, dating it to the period 1876-90.
It came for sale at Halifax Mill Auctioneers (21% buyer’s premium inc VAT) in West Yorkshire on March 10 with a vague catalogue description and a guide of just £30-60.
Knowledgeable enthusiasts found it online and it was bid to £2700.