I would like our readers to know about James and Mary Gage, who are authors and researchers of stone structures of Northeastern America. Here are some of James Gage’s remarks that he made on June 6, 2011, about the 1864 Arch Bridge.

“Overall Observations

           The arch culvert is in excellent condition. There is little evidence of deterioration. The workmanship is superb. The interior stones of the arch have a higher level of finished surfaces than the foundation support stones. The arch stones have closely spaced parallel striations which is a type of finished tooled surface. This level of finish work is a bit unusual.

The stones were cut, shaped, and finished by skilled artisans. The assembly of the culvert would have been overseen by a master stone mason. Carpenters would have been needed to construct the support framework to hold the arch in place during placement of the stones. Laborers would have been needed for transporting, hoisting, and positioning the stones.

The standard practice of 19th century railroads was to reserve the best quality construction work for bridges and culverts in the most remote areas. The logic being that the most remote and difficult-to-access structures needed to be built to minimize maintenance and repairs. This arched culvert was certainly built to meet that requirement."

"Mason Marks:

These are the first 19th century mason's marks we have seen on a structure. Mason's marks on Medieval European structures are fairly common, but references to them on 19th century structures are scarce.

Although the medieval mason's marks have been extensively studied, there are a number of divergent opinions as to their purpose (and little agreement.)

            A few observations: The tunnel façade is constructed of carefully fitted voussoir and spandrel stones. The “Oklahoma” stone is an excellent example. Such careful fitting of stones usually suggests  planning and prefabrication at the quarry rather than onsite trimming to fit a particular spot in the wall.

In other words, I think the entire façade was carefully cut and assembled at the quarry’s cutting sheds and then disassembled and shipped to the job site for reassembly. This approach would require the careful numbering of all of the blocks. This is one potential explanation for the roman numerals on some of the blocks. Obviously not all the blocks have visible numbers. It is possible that most of the blocks were numbered on top and therefore the numbers are no longer visible and or some of the numbers were painted on rather than carved. The other possibility is that only certain blocks were numbered and used as control or survey points as a reference for the placement of the remaining blocks. It is reasonable to state that roman numerals were an integral part of construction and assembly of the culvert.

            Sandstone forms in stratified layers and usually has a specific direction to the grain. Sandstone generally needs to be positioned in the structure so that grain runs in a particular direction. Some sandstone blocks need to be positioned such that their top and bottom are the same as when removed from the quarry. Failure to properly position the block can result in spalling, cracking, crumbling, and rapid weathering of the blocks. You thought the triangular symbols might have been used to denote the correct position of the blocks. This sounds like the most logical explanation."

"Chisel Marks:

The widely spaced chisel marks cut diagonally across the surface of some of the stones was a common technique for removing the high points on a stone’s surface. It was considered a rough finish."

"Spillway Stones:

The purpose of these stones was to prevent the water from undermining the foundation of the tunnel. This also indicates that the tunnel’s foundations were built on soil rather than bedrock."

"Estimates of Stone Used in Construction:

These are rough estimates based upon the dimensions provided. They do not reflect any below- grade foundation stonework.

Tunnel Base Wall [one side] 72.25’ L x 8.5’ H x 2.25 W = 1377 ft3 x 2 walls = 2754 ft3

Arch 72.25’ L x 31 ft2* = 2240 ft3

Wing Wall (one side) 18’ L x 25’ H x 2.75’ W / 2 = 619 ft3 x 4 walls = 2476 ft3

Parapet 15’L x 6’H x 3.75’W = 338 ft3 x 2 parapets = 676 ft3

Estimated total stone in construction = 8146 ft3

Weight of sandstone ranges from 135 to 150 lbs per cubic ft

Estimated weight of stone in construction 550 to 611 tons

Parapet stone 24.5 ft3 = 1.65 to 1.8 tons

Wing wall stone 18.4 ft3 = 1.25 to 1.38 tons

Base stone 25 ft3 = 1.69 to 1.88 tons

*This number was calculated by subtracting the area of circle of 10’ radius from 11.5’’ radius and

dividing by 2 (i.e. the arch is ½ a circle)”

             I consider James and Mary Gage to be two of the leading experts on stone structures in America today. They have shed wonderful insight on the 1864 Arch Bridge and their help is greatly appreciated.

From there website:

            Mary Gage and James (mother & son) have been researching stone structures in the Northeastern United States since 1992. Their research has focused on historic agricultural farm structures, stone quarrying technology & methods, and Native American ritual stone structures and landscapes. They have authored journal articles, several books, produced a forty minute documentary film, and maintain the website www.stonestructures.org.