to its mouth it is a broad, deep, sluggish stream. About from its mouth the Hudson breaks through the rocky barrier of the highlands, forming the most easterly of the Appalachian Mountain ranges; and along its lower course it is bordered on the west by a nearly perpendicular wall of basaltic rock high, known as The Palisades. Above Troy, the Hudson receives the Hoosic River from the east and the Mohawk River from the west. The former stream rises in western Massachusetts and Vermont, and the latter near the center of New York. At Little Falls and The Noses, the Mohawk breaks through mountain barriers in a deep, rocky ravine; and at Cohoes, about from its mouth, it flows down a perpendicular precipice of . Below Troy the tributaries of the Hudson are all comparatively small streams. South of the highlands the river spreads out into a wide expanse known as Haverstraw Bay. A few small streams upon the extreme eastern border of the state flow eastward into the Housatonic River, and several small branches of the Passaic River rise in the southern part of Rockland County. Lake Erie forms a portion of the western boundary of the state. It is long, with an average width of , and it lies mostly west of the bounds of the state. It is above Lake Ontario, above sea level, and has an average depth of . The greatest depth ever obtained by soundings is . The harbors upon the lake are Buffalo, Silver Creek, Dunkirk, and Barcelona. The Niagara River, forming the outlet of Lake Erie, is long, and, on average, more than a mile wide. About below Lake Erie the rapids commence; and further below are Niagara Falls. For below the falls the river has a rapid course between perpendicular, rocky banks, high, but below it emerges from the highlands and flows to Lake Ontario in a broad, deep, and majestic current. Lake Ontario forms a part of the northern boundary to the western half of the state. Its greatest length is and its greatest width is . It is above sea level, and its greatest depth is . Its principal harbors on the American shore are Lewiston, Youngstown, Port Genesee, Sodus and Little Sodus bays, Oswego, Sackets Harbor, and Cape Vincent. The St. Lawrence River forms the outlet of the lake and the northern boundary of the state to the