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 riot a visionary project. The plan which was adopted as the most suitable under all the considerations of economy and security to the work, was a Low Bridge to support an inverted syphon of iron pipes and the design of it was as follows adjacent to the ; :

southern shore of the river there was to be constructed an arch for the channel of the river, of 80 feet span and springing from abutments 10 feet above high water level ; this

would form a passage of 80 feet wide, and the height from high water level to the under side of the arch at the crown would be 50 feet : south of this arch followed three other arches on the slope of the rocky hill, of 35, 30, and 25 feet span : south of these arches a foundation wall was designed to continue the plane of inclination to the level of the Aqueduct. From the large arch to the northern shore of the river an embankment of stone was designed for the support

of the pipes, and from this wall the table land on the northern shore and the slope of the northern side of the valley, would be excavated to a form to give the proper position to the pipes descending from the Aqueduct. The lowest level of the top of this stone embankment was designed to be 4 feet above flood tide. Suitable parapet walls were designed to be built along the sides of the embankment to sustain a covering of earth over the pipes. With the form which was given to this inverted syphon, four pipes, each of 3 feet interior diameter, were found to give a discharge of water equal