In Fig. 236 is shown a stone arch on the New York, New Haven & Hartford Railroad at Pelhamville, N. Y. This arch was constructed over a highway, and the length of its axis is sufficient for four overhead tracks. The span is 40 feet, and the rise is 10 feet above the springing line, the latter being 7 feet 6 inches above the roadway. The length of the barrel of the arch is 76 feet.

The arch is a five-centered arch, the intrados corresponding closely to an ellipse, the greatest variation from a true ellipse being 1 inch. The theoretical line of pressure is well within the middle third, with the full dead load and partial live load, until the short radius is reached, where it passes to the outer edge of the ring-stone, and thence down through the abutment. There is a joint at the points where the radii change, to simplify the construction.

The stone is a gneiss found near Yonkers, N. Y., except the keystone, which is Connecticut granite, and the coping, which is blue-stone from Palatine Bridge, N. Y.