 For this purpose it was placed aboard the 50-gun , which set sail from Portsmouth on 18 November 1761.Harrison, by then 68 years old, sent it on this transatlantic trial in the care of his son, William.The watch was tested before departure by Robertson, Master of the Academy at Portsmouth, who reported that on 6 November 1761 at noon it was 3 seconds slow, having lost 24 seconds in 9 days on mean solar time.