Glossary of Canal Terms
Locks
Locks are required on most canals to lift and lower the boats over changes in elevation. (The Suez Canal is unique in that it is was cut across level ground and has no locks). On the D&H Canal, the locks generally had 10 feet of lift, although the ones on our Five Locks Walk average 12 ½ feet- they “lost” 2 locks in the final enlargement of 1850, consequently these locks needed more lift to compensate. Locks use miter gates, where the gate or gates are angled so that the water pressure keeps them closed. Leonardo DaVinci invented the miter gate circa 1500!
Aqueducts
When a canal crosses a body of water, it is carried in an aqueduct- otherwise the canal would lose its hard-won water! The D&H needed 20 aqueducts as well as numerous culverts to allow other streams to pass under the Canal safely. Between 1847 and 1850, John Augustus Roebling built 4 suspension aqueducts for the D&H Canal Company- over the Delaware River, the Lackawaxen River, the Neversink River, and the Rondout Creek in High Falls. (Only the one over the Delaware survives, administered by the National Park Service.) They built a 2-arch Roman-style stone aqueduct over the Rondout in High Falls, superseded by the Roebling suspension aqueduct in 1850- all the other D&H aqueducts had masonry abutments with wooden trunks.
Bridges
The D&H Canal Company built 168 bridges to maintain property access to the lands the Canal was cut through. Originally many of these were wooded pony-truss bridges, the trusses covered with vertical boards to protect them from the elements. The photo at the right shows High Falls c1860 with a pony-truss covered bridge over the Canal. The building to the right of the bridge is the home to our museum, the DePuy Tavern. In the latter period, iron-truss bridges designed by Squire Whipple were used.
Waste Weirs
Canals require a way to drain the water off, for repairs and enlargements. The water was drawn down in the fall, to, as the Canal typically operated from April through November. Waste weirs are stone cuts, usually in the towpath (river) side with a wooden gate that could open to let the water out.
Guard Gates
Canal Locks could be used to isolate sections of the Canal when water had to be drawn off but the Canal also had guard gates. (Labeled stop locks in the Pennsylvania section.) Stone on both the berme and towpath sides held boards to block the water.
Basins
There were two types of basins- those that were purpose-built and those formed by tributaries of the river the canal was constructed alongside. It was easier to just let water fill the tributary’s “valley” rather than bring in earth to fill. These wider sections of the Canal allowed industries access to water out of the way of traffic. There were places that basins were purpose-built, most notably the one in Hawley PA that was built for the Pennsylvania Coal Company’s boats. They had their own gravity railroad that terminated there to transport their coal to the D&H Canal for transport to market.