An officer of the King's, who had been a prisoner, was lately brought through the post of Ticonderoga, and reports that the rebels were at work upon their fleet for next season, and says that they had laid the keels of 26 boats, large and small. The General [Carleton] has, on our part, laid the keels of six, one of which is to be a 20 gun ship. Little is to be apprehended from these preparations of the rebels, who are in want of artillery, and all manner of articles for equipping a fleet, and have applied to Philadelphia for shipwrights, without success, that city having no assistance to spare, from the consideration of its own defence.