You can find a description on page 750. Describes it as follows; "rises near the Suncook Pond, and flows north through a deep and rapidly descending valley-bottom to the lake, and is called Miles River, or Leavitt's Brook, taking its name from two men by the name of Leavitt, Miles and Samuel, who had mills on it. It drains the eastern side of Mount Major and Gunstock and the western side of Mount Prospect."
I can't find it named on any map that I have,for either name, but I have a book "The Old Maps of Belknap County, N.H. in 1892" and on the map of Gilford it shows a river or stream that could be the one, from the above description. Hope this helps somewhat.