Last year the Museum was lucky enough to be given a very rare book that shows how quickly the details of John Harrison's sea-watch, H4, were disseminated around Europe. Danish-Principles-TitleEntitled Historien af Mr Harrisons Forsög til Laengdens Opfindelse Formedelst et Uhr eller en Tidmaaler, the book includes a translation into Danish of The Principles of Mr Harrison's Timekeeper (1767), which was published by the Board of Longitude to make the details of H4's construction more widely available. The preface is dated 10 December 1767, so it was produced within nine months of the original, which is only slightly slower than a French translation by the mathematician and hydrographer Esprit Pezenas. Like the French edition, this version includes reproductions of the drawings from the original.Danish-Principles-Fig-1Danish-Principles-Figs-14-1As well as a full translation of the Principles, the book contains an abridged version of Nevil Maskelyne's An Account of the Going of Mr. Harrison's Watch (1767), describing the trials of H4 at the Royal Observatory, and a summary of Harrison's uncomplimentary reply, Remarks on a Pamphlet lately published by the Rev. Mr. Maskelyne (1767). On top of that, the first 30 pages tell the story of Harrison's work up to 1767.

The book was put together by Christian Carl Lous (1724-1804), who had been Navigationsdirektor at the Danish Naval Academy in Copenhagen since 1763 and so had knowledge and an interest in longitude matters. Lous wrote several works on navigation and submitted a number of schemes to the Board of Longitude, including proposals for a new telescope and other ideas. There's also some other surviving correspondence between him and Sir Joseph Banks, as well as compasses to his design. He seems to have been busy as a translator too - he translated both Milton's Paradise Lost and Alexander Pope's Essay on Man into Danish.

Lous is, I'll admit, another on my list of people to look into, when time permits. In the meantime, I'd love to hear from any Danish speakers who can tell me more about this work, particularly the narrative set out in the first part.