I have just answered my own question (partially)
This from my other notes ...
Henry Duncan's daughter Isabella married Lt. Thomas Twisden of HMS "Adament" at Halifax 14 December 1790 and the notice of marriage was carried in the Halifax Royal Gazette 21 December 1790.

Does the entry contain any further details?

Does this newspaper contain death notices for Arthur French Duncan (30 September 1790 ), Isabella M Twisden (21 August 1792), Thomas Twisden (4 October 1801 - at sea off Newfoundland) or (hope against hope for this one) Henry Duncan (November 1802 - also recorded as 1801-, at sea off Newfoundland - the loss of the ship Scout)
Any assistance appreciated
daryl