E.I. DENT'S PATENT MERIDIAN INSTRUMENT (DIPLEIDOSCOPE)
04-010. English, mid 19th century, signed on the cover "E.I. DENT'S PATENT MERIDIAN INSTRUMENT. 82, Strand, & 33, Cockspur St. LONDON". Made of heavy cast brass, the decorative base is 2 1/8" wide x 3 3/8" long, with the mirror cell atop, and standing 2 3/8" high overall. The mirror cell cover is 2 1/4" diameter, made of bright polished brass. This attractive dipleidoscope is in very good overall condition.
The dipleidoscope was patented in 1843 by James Bloxam and marketed by Edward Dent for timing the meridian transit of the sun, accurate to a few seconds, i.e. solar noon. The mirror cell contains a hollow, right-angled prism, with two sides silvered and one of glass. The meridian transit was determined by the coincidence of two images of the sun by single and double reflection, one from the top glass and the other from both mirrors. With the base properly leveled and oriented, the meridian transit could be read to seconds.
