Stone Definitions

Background-During the early nineteenth century, the engineers of the Chesapeake & Ohio Canal elected to use cut stone for most of the substantial structures along the system. The Catoctin Aqueduct is no exception.

The face stones for the Catoctin Aqueduct were obtained from the granite quarries of the Patapsco River. They were transported forty-six miles on the Baltimore & Ohio Railroad to the Point of Rocks, and then taken by wagon three miles to the aqueduct construction site. The stone was worked and finished by masons at the aqueduct site.

Ring Stone: One of the individual masonry units, or cut stones, of an arch, usually wedge shaped with the abutting faces aligned with a radius of the center.

Key Stone: The central wedge-shaped stone of an arch that locks the Ring Stones together. This is the most important stone in the arch. 

Towpath Coping Stone: A stone covering the top of the aqueduct parapet wall that caps the wall and gives it a finished appearance. Typically, the coping stones overhang the parapet walls to provide a drip for rain. On C&O Canal aqueducts, the coping also served as the towpath. 

Water Table Stone: The projecting decorative molding of the aqueduct parapet walls at the point just above the structure’s arches. 

Spandrel Stone: The stones located in the portion of the aqueduct’s walls between the arches. 

Parapet Stone: The cut stone “blocks” that comprise the walls above the aqueduct arches. 

Berm Coping Stone: A stone on top of the aqueduct parapet walls, opposite side of the towpath coping that protect the wall and give it a finished appearance. Also called capstones. 

Prism Stone:  A stone that forms the channel through which the canal water flows in an aqueduct. This part of the aqueduct is also called the “trunk” of the aqueduct.

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