The Royal Navy, desperate for seamen, was in theory looking for its deserters as well as cargo coming to or from France. Though armed with a Seaman’s Protection Certificate proving American nationality, an American, again in theory, could not be "impressed;" in practice the British often seized what hands they needed without particular regard for legal niceties. The French, as were Portland privateers in several wars, were interested in both disruption of trade, particularly in the Caribbean, as well as tidy profit from prizes. In this particular case, Captain Clapp, headed for Europe, was captured by Sir Sidney Smith of the Royal Navy and his vessel taken to England as a prize. Though it took him six months to accomplish it, Captain Clapp managed to get his vessel released by the High Court of Admiralty, his cargo paid for, and so skillfully did he manage things that his owners made a tidy profit from the whole affair.
Captain Clapp retired from the sea in 1796 and became one of Portland’s leading merchants, trading cotton and flour with the American South, fish, molasses and lumber with England and Germany, and importing iron and sailcloth from Russia. Though badly hurt by the Embargo of 1807, the patriotic captain, who "enjoyed a higher credit than any other American merchant of his time," donated more than half his fortune "to sustain the national credit" and enlisted as a volunteer soldier during the War of 1812, even though he was then in his fifties. After the war, in 1817, he entertained President James Monroe at his elegant mansion (which had the first cupola seen in Portland) and in 1847 President James Polk visited him. Clapp died in 1848.
When the Marine Society was founded, Certificate Number One was that of its president, Captain John Thorlo. By 1796 Thorlo had apparently recovered, at least to some degree, from the loss of his house and many possessions in Mowat’s 1775 bombardment, and apparently was well enough thought of to be entrusted with the command of the sloop Portland Packet, which carried the United States Commissioners entrusted with settling the boundary dispute with Canada from Boston to their first meeting in Halifax. Aboard besides several "gentlemen passengers" were the Hon. David Howell, Esq. and the Hon. James Sullivan, Esq.
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