'SIR: In answer to your favor of yesterday, I must inform you that I have often been told of the advantages of Point Alderton, with respect to its command of the shipping going in and out of Boston harbor; and that it has, before now, been the object of my particular inquiry. I find the accounts differ exceedingly in regard to the distance of the ship-channel, and that there is a passage on the other side of the Light-House Island for all vessels except ships of the first rate. My knowledge of this matter would not have rested upon inquiry only, if I had found myself, at any one time since I came to this place, in a condition to have taken such a post. But it becomes my duty to consider not only what place is advantageous, but what number of men are necessary to defend it; how they can be supported, in case of an attack; how they may retreat, if they cannot be supported, and what stock of ammunition we are provided with, for the purposes of self-defence, or annoyance of the enemy. In respect to the first, I conceive our defence must be proportioned to the attack of General GATES' whole force, leaving him just enough to man his lines on Charlestown Neck and Roxbury; and with regard to the second and most important object, we have only one hundred and eighty-four barrels of powder in all, which is not sufficient to give thirty musket-cartridges a man, and scarce enough to serve the artillery, in any brisk action, a single day.