OF RAILS, ROPES, AND ROCKS: TERRAIN AND ENGINEERING GEOLOGY ALONG THE DELAWARE & HUDSON (D&H) CANAL CO. AND PENNSYLVANIA COAL CO. (PCC) GRAVITY RAILROADS IN NORTHEASTERN PENNSYLVANIA

During the 19th century two gravity-railroad systems were vital to the transportation of coal from the mountain-rimmed Northern Anthracite field in northeastern Pennsylvania to markets in New York City. The “gravities” connected anthracite mines in the Lackawanna and Susquehanna River valleys to the D&H canal—and, later, to the Erie railroad—in the valley of the Lackawaxen River, a tributary of the Delaware. Both the D&H (1829-1899) and PCC (1850-1885) railroads had separate loaded-car and empty-car (light) tracks that consisted of alternating inclined planes and “levels” on each track. (The two tracks were generally close together on the D&H, but locally miles apart on the PCC.) Stationary steam engines were utilized on the relatively short inclined planes, and the cars moved by gravity on the much longer, gently sloped levels.

The two railroads made use of natural swales or breaks in crossing the Moosic Mountains. The D&H loaded- and light-tracks passed through Rix’s Gap, a shallow wind gap due east of Carbondale. On the PCC gravity, the loaded track ascended the east side of the Roaring Brook water gap at Dunmore in order to attain the elevation necessary to coast on a 14-mile level, while the light track returned through the gap on a 20-mile level. To obtain that gentle, 20-mile-long downgrade, the PCC light-track utilized one of the abandoned outlet gorges of Glacial Lake Wallenpaupack (with four “dry” waterfalls over ledges of Catskill Formation sandstone) and the postglacial Nay Aug Gorge (through conglomerates and sandstones of the Pottsville and Mauch Chunk Formations), both within the drainage basin of Roaring Brook.

Other sites of geologic and engineering significance along the old gravities are the “Shepherd’s Crook” switchback and nearby Panther Falls (Pottsville Formation) on the steep mountain slope west of Rix’s Gap (D&H light); the Greenville Cliffs (Spechty Kopf Formation) on Mt. Cobb southeast of Dunmore (PCC loaded and light); a 755-foot-long, unlined rock tunnel (Catskill Formation) at the crest of the Moosic Mountains (PCC loaded); and a spectacular monocline in otherwise flat-lying rock strata (Catskill Formation) at Wangum Falls near Hawley (PCC loaded).