A WOLLASTON-TYPE REFL. GONIOMETER by C. GRINDEL ca 1820

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A rare early 19th-century Wollaston brass reflecting goniometer signed: Carlo Grindel with engraved scale and vernier read-out, with adjusting wheels raised on a brass frame, on turned walnut base. Dimension: base diam. 6" (15 cm); height 7" (18 cm) Carlo Grindel (1780-1834) was a mechanician from Milan who worked at the Brera Astronomical Observatory. He produced some instruments for celestial observations as well as compasses and drawing instruments. The present goniometer is THE ONLY ONE known to exist signed by him. The Reflecting Goniometer was invented by William Hyde Wollaston (1766-1828) in 1807 { Phil. Mag. , 27 (1807). Wollaston's device was used to measure the angles between the plane surfaces of crystals. " It consisted of a brass circle, graduated on its edge and mounted on one end of a horizontal axis. The crystal to be measured was mounted on the other end of the axis. The observer adjusted the crystal until a distant image was reflected off one of the facets into the observers eye, rotated the crystal until the next surface reflected the same image (the eye being kept stationary), and then read the angle between the two crystal faces from the graduated circle ." (From Steven C. Turner, "Goniometer" in Instruments of Science , Robert Bud and Deborah Jean Warner, eds (Garland Publishing, New York, 1998, pp 29 read more

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