By a letter which the. editors received from Pass Christian, dated Sept. 17th, 1813 They are informed that Gen. Flournoy and Com. Shaw were to set out from that place, the next day, for the Mobile. The general had received information that a British vessel had just* arrived at Pensacola, having on boat'd a large! .quantity of ammunition and two Slt;rniino'e ln-\| tfiuii chiefs, vvlio hold the rank of RitioAiUKK, Glnerals in the British service. Gen. Flour-1 noy had ordered the regular forces in that quarter with the 3d regiment, to the Mobile