![H1 to H4. A series of time keeping devices made by John Harrison in order to collect the £20,000 prize offered for the solution of the The Longitude Problem, which required a H1 to H4. A series of time keeping devices made by John Harrison in order to collect the £20,000 prize offered for the solution of the The Longitude Problem, which required a](https://i.redd.it/ho9u36e1xb431.jpg)
H1 to H4. A series of time keeping devices made by John Harrison in order to collect the £20,000 prize offered for the solution of the The Longitude Problem, which required a
![Derek Pratt's Reconstruction Of John Harrison's H4, The World's First Precision Marine Chronometer (Part 1 of 3) - Quill & Pad Derek Pratt's Reconstruction Of John Harrison's H4, The World's First Precision Marine Chronometer (Part 1 of 3) - Quill & Pad](https://quillandpad.com/wp-content/uploads/2016/12/1-1_Derek-Pratt-H4-BHJ-Feb2015.jpg)
Derek Pratt's Reconstruction Of John Harrison's H4, The World's First Precision Marine Chronometer (Part 1 of 3) - Quill & Pad
![Amazon.com: Harrison's H4 Chronometer : Ferdinand Berthoud : c1767 : Blueprint Giclee Art Print: Posters & Prints Amazon.com: Harrison's H4 Chronometer : Ferdinand Berthoud : c1767 : Blueprint Giclee Art Print: Posters & Prints](https://m.media-amazon.com/images/I/61OUYhKY3VL._AC_UF894,1000_QL80_.jpg)