Construction of the Highbrook Avenue Stone Arch

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Though each day hundreds of Pelham residents pass beneath the Highbrook Avenue stone arch over which the New Haven Line tracks pass, few residents know of its engineering significance. Today's posting to the Historic Pelham Blog provides a photograph of the arch when it was under construction in the mid-1890s and a transcription of excerpts from an early 20th century engineering text describing its significance.

Source of Photograph: French, Arthur W. & Ives, Howard C., Stereotomy, Fig. 42 facing p. 78 (NY, NY: John Wiley & Sons, 1902).

I previously have written about the Pelham Arch. That posting, published on May 24, 2007, also provided a diagram of the arch. See Thursday, May 24, 2007: The New Haven Line Stone Arch Above Highbrook Avenue.

The "Pelham Arch" as the Highbrook Avenue stone arch has been known, is an example of a "five-center stone arch" built by use of the "stereotomy" process to cut the stones used to build the arch. Stereotomy involves the cutting of stones from rough blocks so that when the cut stones are assembled together they will form a predetermined whole. According to one source, the process consists of three distinct parts: "first, the construction of the projections of the structure on as large a scale as convenient; second, the proper division of the structure into blocks and the obtaining of the directing instruments used to cut the blocks; third, the proper order of the application of the directing instruments to obtain the best results." Id., p. 22.

What follows are excerpts from the same text regarding the arch:

"103. Example. -- An excellent example of a five-center stone arch is one built at Pelham, N.Y. (formerly Pelhamville), on the N.Y., N.H. & H.R.R. An illustration of this arch is given in Fig. 42 and Art. 11, with a brief description taken from the Eng. News of Jan. 17, 1895, vol. xxxiii. p. 34."

Source: Id., p. 55.

"FIG. 42. -- THE PELHAM ARCH.*

142. This arch is located on the New York Division of the New York, New Haven & Hartford R. R., at Pelham, N.Y. (formerly Pelhamville). It is a five-center arch of 40 ft. span, with a rise of 10 ft. The intrados corresponds closely to an ellipse, the radii of the three arcs being respectively 5 ft. 7 1/4 in., 20 ft., and 40 ft. A joint was placed at each change of curvature. The geometry of the oval was given in a previous problem (§ 105.) The sheeting and ring stones were all cut in the quarry. The joints are 1/4 in. The surface of the ring stones is rock-faced, with no projections exceeding 1 1/2 in., with a 1 in. chisel draft along the edges. The intrados is bush-hammered. The stone is gneiss, with the exception of the keystones and coping, which are of Connecticut granite and bluestone.

By a careful inspection of the figure many points on construction may be gained.

* Eng. News, 1895, xxxiii. 34. Photograph from Mr. H. B. Seaman, M. Am. Soc. C. E."

Source: Id., p. 78.

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