By a letter which the editors received from Pass Christian, dated Sept. 17th, 1815 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 tveeiv-j ed information that a British vessel ha I just | arrived at I’ensaoda, having on board a large! duantitv of ammunition and taw Scniino'e !n-\ , ! i’Uu chiefs, who hold the rank of B.uoaiukr, .jtiLNT.RALS in the British service. Gen. Flour-! ijnoyhad ordered the regular forces in that * {quarter with the 3d regiment, to the Mobile ; |