The horse- or ox-drawn cars devised by the inventor-engineer Gridley Bryant to convey the massive granite blocks from the “Railway Quarry” and the “Bunker Hill Quarry” in Quincy to the navigable waters of the Neponset River for transshipment to the Bunker Hill monument site in Charlestown have their place in the history of American railroads (see below, p. 307). The cars or carriages had wheels six feet in diameter, the wheels shod with iron half an inch thick and flanged on the inner side of the rim. Suspended by chains from the axles was the load-carrying platform which could be raised or lowered by machinery on the top of the car. Two or three cars could be coupled for conveying blocks twenty feet or more in length. A sixteen-ton load could be carried on a three-car train which moved at a speed of three miles an hour on tracks that descended eighty-three feet in the nearly four miles from quarry to wharf. The tracks were of wood faced with iron and were laid on a bed of broken stone with a gravel surface. See Bowen’s Picture of Boston, 2d edn., p. 286–288; William Churchill Edwards, Historic Quincy, Massachusetts, Quincy, 1954, p. 105–108. Bowen’s representation of a train on the Granite Railway is from Caleb H. Snow, Geography of Boston, Boston, 1830, p. 159.