The channel which separated Morrisania, in Westchester-county, from Montresor'sisland, in the City of New York, being quite narrow, and a heavy picket of four hundred and fifty mounted men having been constantly maintained at Morrisania, the sentries of the respective forces, posted within halfgunshot distance, sometimes fired at each other, in violation of the inconsistent usages of War; and General Heath has recorded some interesting instances of both the friendly and the unfriendly correspondence of these very important minor outposts.'' But a cou2Jle deserters from a man-of-war which was anchored off the island, conveyed such information to General Heath as led him to sujjpose that the entire force which occupied that island could be easily captured ; and, having submitted the subject to the consideration of the General Officers of his Division and to General Washington, and, having received the approval of all, he proceeded to make the attempt. Two hundred and forty men were detached for that purpose ; and the command of the expedition was given to Lieutenant-colonel Michael Jackson and Major Logan and Major Hatfield, the latter of Westchester-county. 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.