This arch presents a singularly bold appearance, vaulting over the roadway and rising high up above the old mill, and what adds much to this boldness, is the narrowness of the arch, or small distance from one end of it to the other; being only 23⅓ feet long at the springing line while the span is nearly four times this length. The length of the arch diminishes towards the crown, the ends being in planes not vertical, but inclining towards each other at the top. Each end has a batter or inclination of one twenty fourth of its height, or half an inch to the foot. The arch is built of granite, is 3 feet thick at the crown and 4 feet at the spring or base. The abutments have a foundation of solid rock which was excavated in proper form to give them firm footing. The whole structure presents a degree of stability which seems to defy the effects of time. The Aqueduct has a cast iron lining over this bridge (as it has over all of this character): it is formed of plates five eighths of an inch thick, put together with screw-bolts and nuts and the joints closely filled with iron cement. This lining is within the brick work of the bottom and sides of the channel-way, having four inches of brick outside of it and four inside. The object of it is to prevent any water dripping through the work, lest by any means it should fill the exterior masonry of the bridge with moisture and thus render it liable to injury from frost. Other precautions are taken in forming the masonry about the channel-way, to prevent this exuding, and the whole plan of the work shows foresight and precaution worthy of the highest praise. From the Sing-Sing Kill the Aqueduct pursues a course along the east bank of the Hudson and the first work of peculiar interest is the Aqueduct bridge over the road from Tarrytown to Sing-Sing; before it reaches this place it passes through three tunnels, over high foundation walls, and encounters deep excavations. [Illustration: XIV _F. B. Tower._ _W. Bennett. sc._ AQUEDUCT BRIDGE FOR ROAD WAY.] Plate XIV. is a view of this bridge: it is eleven and a quarter miles from the dam. The arch is 20 feet span and has a versed sine or rise of 5 feet. From this the Aqueduct passes on, encounters one tunnel, and reaches the valley of Mill River, twelve miles and three quarters from the dam. This River runs through Sleepy Hollow and enters the Hudson about a mile and a half above Tarrytown. The stream is 72 feet below the bottom of the Aqueduct, and the valley being of considerable width required a very heavy foundation wall. Plate XV. is a view of the _Mill River Culvert_: it is 25 feet span and 172 feet long. It is about half a mile east of the road leading from Tarrytown to Sing-Sing, and to follow the course of the stream which passes through it, it is three quarters of a mile to the _Old Dutch Church_, near Tarrytown, which is well known, and familiar to every one who has read Irving’s “Legend of Sleepy Hollow.”