They were to embark, at the new Bridge over the Harlem-river, on board of three large floats ; to be covered by a fourth float, similar to the others and carrying a detachment of Artillery, with a light three-pounder gun; to fall down the Harlem-river, with the ebb, during the night, to Morrisania ; and the calculation was so made that, at daybreak, the young flood should be so much made, at the island, as to cover the flats, at the proj)osed place of landing, sufficiently for the floats to leave Morrisania, and be run ashore. The various sentries, on the line of the Harlem-river, were said to have been informed of the character of the movement, and instructed to permit the exjiedition to pass down the river, without challenging it ; and every promise of a successful result was heard from all who were to be concerned in it or who knew of the proposed plan of operations. Notwithstanding one of the sentries had not been told of the expedition or had misunderstood the Order which had been given to him, and had resolutely disregarded the entreaties for silence which had been made, and had discharged his musket, giving an alarm, the enemy does not appear to have been disturbed ; and the three floats ran up to the place appointed for the landing, without serious opposition, and at the appointed time. But, there, a new and entirely unlooked-for obstruction was encountered. The orders were that the float which contaiiied the three commanding Officers should run ashore, between the other two ; that the two Majors should jump ashore, one to the right and the other to the left,