From Saw-Mill River the Aqueduct passing through one tunnel soon reaches Tibbit’s Brook, which it crosses by means of a foundation wall about 30 feet high and a culvert of 6 feet span, and continues along the south side of the valley of this brook, thence to the Harlem River which it crosses at one mile from McComb’s Dam. This crossing is thirty-three miles from the Croton Dam, and about ten miles from the City-Hall. The distance across this valley is about a quarter of a mile, and the surface of the River is 120 feet below the bottom of the Aqueduct. In all the examinations which were made with a view of bringing water from Westchester County, the crossing of this River, or _arm of the sea_, was regarded as the most formidable work that would be encountered; various plans were proposed, and in presenting these plans the project was such as to call into requisition much talent and skill. An Aqueduct Bridge built of stone, having arches resting upon piers and abutments, was proposed so as to continue the Aqueduct across with its regular inclination. An Inverted Syphon of iron pipes was proposed; the pipes to descend to a level near the surface of the River, and passing along upon a stone embankment rise again and connect with the Aqueduct: in this stone embankment an arch was to be built of sufficient dimensions to allow free passage of the water of the River. [Illustration: XVII _F. B. Tower._ _J. W. Hill._ CROTON AQUEDUCT AT HASTINGS.] Another plan was proposed which, though novel in its application to such purpose, was worthy of consideration: this was to build a Suspension Bridge of wire cables reaching across the valley, supported at intervals upon suitable stone piers. This, maintaining the regular inclination of the Aqueduct, would support iron pipes. The design was a bold one, yet instances where such bridges have been constructed for road-ways afford examples of the feasibility and permanency of the structures, and prove that the application of that principle for this purpose was not a visionary project.