If you really want to get into the history of Harrison's chronometers, a must read is
"Time Restored: The Harrison Timekeepers and RT Gould, the Man Who Knew (Almost) Everything" by Jonathan Betts, published in 2006 by Oxford University Press. Jonathan Betts was the Senior Specialist, Horology, Royal Observatory, National Maritime Museum, Greenwich and the biographer of Rupert T. Gould who initially restored the chronometers when no one really understood their significance. The book may be out of print but they are around. Highly recommended.