Napier carried out a series of experiments, measuring errors in compass navigation, and published his findings in 1851.
This was called Napier's Diagram, and it was a graphic method of correcting deviation of a ship's compass, which is still referenced in navigation books.
Exhausted from the frantic schedule required to build HMS Erebus in 1856 for the British government during the Crimean War, Napier in 1857 left the shipbuilding business he had been running for the previous 15 years and started other, less successful ventures.
He started his own shipyard shortly thereafter, but soon closed the business, citing his failing health, and took an interest in the West of Scotland Fishery Company, but this venture too proved unsuccessful.
[2] James Robert Napier died in Glasgow in December 1879, after contracting an illness while boating on Loch Lomond.