quadruple-rate folded letter to Boston with "Manchester Ju 30 1848" datestamp, endorsed "pr. Niagara Steamer" with manuscript "4/-" rate, carried by Cunard's Niagara departing Liverpool July 1 and arriving Boston July 12, upon arrival rated "72" retaliatory rate, small tear at top, otherwise very fine and rare, the British rate structure didn't allow for triple rates, increasing from a double rate of 2sh for ½oz to 1oz to a quadruple rate of 4sh for 1oz to 2oz, in America letters from 1oz to 1½oz were rated triple (with 72c here representing three times the 24c retaliatory rate), covers showing the disparity in rate progression between the two countries are rare