Letter, introducing George Fisher's paper 'On the errors in longitude as determined by the chronometers at sea, arising from the action of the iron in the ships upon the chronometers' from John Barrow to Wm [William] Thos [Thomas] Brande The paper to which the letter refers is found at PT/14/18. Subject: Navigation Written by Barrow at the Admiralty Office. This letter was not published in Philosophical Transactions. 6 May 1820