Explored Greenland
Alexander Nisbet (p.164) states (quoting Torpheus's 'History' p174) that this Henry St.Clair 'of Roslin' was created Earl of Orkney by Haco, King of Norway, circa 1379. Nisbet also mentions that this Henry was also Lord of Zetland, and was created Duke of Oldenburgh in Denmark.
On p119 (vol.1) of Nisbet's 1984 reprint, it is stated that this Henry St.Clair made an obligation to sir James Sinclair [sic] of Longformacus, his cousin, and that it was dated 22nd June 1384 at Roslin.
Another reference on this famous family is "The Saint-Clairs of the Isles" by Roland William Saint-Clair, Auckland, 1898.