NavList:

The first ever backward sight taken by a reflecting quadrant on board any vessel at sea was

accomplished on September 1^st (os) 1732 by John Hadley.

The vessel was HMS Chatham and the location was the Thames estuary. These were part of the famous/infamous trials ordered by the British Admiralty in response to Hadley’s claim on a portion of the Queen Anne longitude prize and were overseen by the Astronomer Royal Edmond Halley.

John Hadley did not receive any award and neither did any other reflecting quadrant/sextant inventor because the terms of the longitude prize precluded any device invented prior to passing of said act.

Mind you, Hadley’s instrument, although marginally superior to that of Thomas Godfrey, required a deal of “figure jiggling” in order to produce convincing data as is fairly obvious from the report of the sea trial.  I have a PDF of this if anyone is interested.

A picture of Hadley’s instrument can be viewed on the Royal Society’s special trailblazing web site at http://trailblazing.royalsociety.org  as a backdrop to the second 50 year section. A description can then be accessed by clicking on the red button for the year 1730.

Ted Gerrard
tedgerrard@btinternet.com
www.samosbooks.org