The remote sources of the Hudson River are in Hamilton and Essex Counties, in the Adirondacks, in northeastern New York State, the highest at four thousand feet elevation above the sea, the head streams being outlets for a large number of highland lakes. The river flows over three hundred miles to the sea, and has few tributaries, the largest being the Hoosac and the Mohawk. Its lower course is a long tidal estuary, the tidal head being at Troy, from whence the fall in level to the ocean is only about five feet. The estuary below Manhattan Island expands into the noble New York harbor, enclosed between Long Island on the east and Staten Island on the west, the latter being the Indian Aquehonga, meaning the "high sandy banks." The harbor entrance from the sea, at Sandy Hook, is eighteen miles below the city. Inside Sandy Hook is the lower bay, of triangular form, extending nine to twelve miles on each side, the Narrows, a deep channel about a mile wide at the northeastern angle, opening into the upper bay, which is an irregular oval, about eight by five miles. This extends northward into the Hudson River, westward into Newark Bay, and has the tidal strait of East River leading north to Long Island Sound, on the eastern side of Manhattan. Within the bays and rivers around New York there are over a hundred miles of available anchorage ground, and the Government is now making a channel to the sea through Sandy Hook bar, forty feet deep at low water. ENTERING NEW YORK HARBOR. The approach from the sea to Sandy Hook is first guided for the modern navigator by the flashing white light on Fire Island, a low sand-strip on the Long Island Coast; and then there rise in front the Highlands of the Navesink, on the Jersey Coast south of Sandy Hook, with a pair of twin lighthouses perched upon their green slopes. The Hook, a long strip of yellow sand enclosing the harbor, also has another lighthouse on its northern end. Here are the expanding works of a formidable fort defending the harbor entrance, and an artillery trial and proving ground. Behind the Navesink Highlands and the Hook, the Jersey shore of the lower bay stretches far back westward into Raritan Bay, thrust up into the land between New Jersey and Staten Island. The green hills of this island, crowned with villas, make the northwestern boundary of the bay. To the right hand of the Hook, and north of the entrance, is the sand strip of Coney Island, with its stretch of hotels and buildings, the popular seashore resort of New York. Within the Hook is the lower Quarantine on the west bank of Romer Shoal, and over opposite is Gravesend Bay, behind Coney Island. The Narrows, where the Hudson has forced an outlet through a broken-down mountain range, is partly obstructed by an island reef of rocks. The hill-slopes, together with the island, are fortified, Forts Hamilton and Tompkins being on either hand, named after Alexander Hamilton and Daniel D.