Transatlantic cover to Boston

August 29, 1851

August 29, 1851, folded letter from London to Boston posted at the Lombard Street post office in London. Letter marked in London for 19-cents debit to the US. It was carried by Cunard steamship "Niagara" from Liverpool to New York, where it was marked for 24-cents postage due, the convention rate for an unpaid letter up to .5 ounce. Since a British contract mail steamer carried the letter across the Atlantic, the UK was entitled to 3-cents inland fee and 16-cents sea postage under the convention. The US retained 5 cents.