This very early quadrant, made soon after Hadley's patent expired in 1747, has many features common to examples from this period. First, it is large for a quadrant. The larger size allowed the index arc to be engraved and read with more accuracy. Second, the instrument has two sighting locations- one on either arm. The normal forward observation was taken with the right sight. This instrument has only a 90 degree arc on the index. Later, larger indexes eliminated the need for the second sighting position which was used to take backsights. Third was the use of the diagonal scaler for dividing the increments of the index scale. Theoretically very accurate, in practice this index was difficult to read. Fourth is the fact that the instrument is made primarily of wood and uses peep holes, not telescopes which were very expensive at the time.
This example is in outstanding condition for its age, and it is very rare to find these quadrants still at this level of quality.
The instrument has a bone inlay in the center engraved with the maker's mark: Urings Facit London or Made in London by Urings. Under the engraved mark is a handwritten mark that appears to be the owner's name, perhaps Burns. The piece is made of mahogany, boxwood, bone and brass. John Urings II is known to have made a variety of different instruments including backstaffs, telescopes, octants and microscopes.
This instrument was part of a 1987 exhibition at the Pacific Asia Museum entitled "Trade and Treasure. Repercussions of the China Trade and its Impact on Maritime Technology."
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