He entered the Royal Navy as a surgeon, and sailed from Plymouth in the frigate HMS Nisus on 22 June 1810.
His next expedition, also in the Nisus, was to Table Bay (February 1812), St. Helena (January 1813), Rio de Janeiro (October 1813), and Pernambuco (December 1813).
In the same year he was ordered to accompany the first regiment of imperial Russian guards from Cherbourg to St. Petersburg, and in 1815 he was on the coast of La Vendée, and was present at the surrender of Napoleon on 15 July.
[1] Prior was elected member of the Royal Irish Academy and Athenæum Club in 1830, and made a Fellow of the Society of Antiquaries of London on 25 November that year.
[1] When John Forster brought out in 1848 his Life and Adventures of Oliver Goldsmith, he was accused by Prior of wholesale plagiarism.