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Description: | M.2. (Green and Lloyd catalogue number in white paint on the box). 28 (Kelvin 1893 ? bequest number in red cellire on the box). 2 (in white chalk inside the lid of the box). 2 (Gardner*& Neil* Belfast* (in black on an ivory maker's trade plate). 0-100 (degrees marked in units of 10 on an ivory arc scale). 0-20 (on an ivory vernier scale). 31 ba/a 3 1/2 (written in black ink on a small ivory plaque on the back of the instrument). MANU Gardner & Neil. early 19th century Belfast, Northern Ireland. DES after HADLEY,John. 1731 London, England. DES after DAVIS,John. 1594 London, England. This is a nine and three-quarter inch ninety degree reflecting quadrant was owned by Professor James Thomson senior, father of William thomson Lord Kelvin. It has a 240 mm radius scale with divisions of twenty minutes and can be read to one minute. It has a single vertical and an arched strut with a reinforced index arm with a tangent screw clamp. It also has a single pinhole foresight with a double pinhole backsight. Only three shades are extant one set probably of three is missing. In fact this instrument, a developement of the back staff, is in reality an octant since the mirror halves the scale. In modern usage allsuch instruments are now called sextants regardless of the size of the scale. | License: | http://www.hmag.gla.ac.uk/spirit/rights/ | Publisher: | Hunterian Museum and Art Gallery, University of Glasgow | Rights holder: | Hunterian Museum and Art Gallery, University of Glasgow | Subjects: | SCIENTIFIC COLLECTION : | Source: | Hunterian Museum | Creator: | Hunterian Museum and Art Gallery, University of Glasgow | Identifier: | http://www.huntsearch.gla.ac.uk/cgi-bin/... | Language: | en-GB | Go to resource |
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