During the Delaware and Raritan Canal’s period of operation, mile-markers were placed at along the canal at an angle to the towpath. Originally made of wood, and later in cast concrete, each marker displayed two numbers. Going downstream from the summit of the canal at Trenton, the number facing the mule driver told him the distance that remained from that point to New Brunswick. Turning around, the driver could read the number that gave the mileage back to the main canal’s point of origin in Bordentown. Together these numbers always totaled 44, which was the length in miles of the main canal. The 22/22 mile-marker located north of Rocky Hill is significant in that it is slightly more ornate than the others, given its location at the half-way point of the main canal.
Documents prepared by the Delaware and Raritan Canal Commission, New Jersey Water Supply Authority and the Department of Environmental Protection employ the use of certain terms to describe the engineering, structures, history and people associated with the Delaware and Raritan Canal. The following is a glossary of canal-related terms compiled from the Commission’s records to inform and assist the public when reviewing documents related to the canal.
Canal: An artificial waterway used for navigation.
Feeder: An artificial waterway used to conduct water to a canal; may also be navigable.
Slackwater Navigation: A navigation system that uses dams to form large pools of water, which are in turn linked by locks and short canals. The natural topography of the Delaware and Raritan Canal made the use of slackwater navigation unnecessary.
Water Power Canal: A small canal built to convey water for industrial or municipal use. The most well-known canal of this type in New Jersey was the Trenton Water Power Canal, which powered industrial development along the Delaware River in the 19th century and was unrelated to the Delaware and Raritan Canal.
Banks & Berms
Bank: The side of the canal, usually the water edge and top of a berm.
Towpath Bank: The bank upon which the towpath is located, usually the river side where the mules walked.
Berm Bank: The bank opposite the towpath bank, generally narrower and not as well-graded and supported with foundation materials as the towpath bank.
Berm: An embankment that forms the side of the canal that keeps the water in, and the surrounding streams and rivers out. The berms on the Delaware and Raritan Canal are built up around brick-like hardened clay cores that are trapezoidal in cross-section and extend the full length of the canal and feeder on the towpath (river) side, and along both sides in low-lying areas. The waterproof clay lining consisted of a mixture of clay, sand, and limestone known as “puddle,” which was applied to the floor and sides of the canal and allowed to harden. Significantly high berms were fabricated along the rivers along the Delaware and Raritan Canal to support the canal at an elevation necessary to sustain even water levels between the locks.
Bulkhead: When used in the context of the canal, a bulkhead is a limiting wall or lining, usually constructed of steel sheet piling, which is built along the inner sides of the canal, particularly in urban areas such as the cities of Trenton and Lambertville.
Flood Guard Berm or Levee: An embankment or dike, generally parallel to a canal or other waterway, which protects it from floods in adjacent areas. Flood guard berms were constructed on the Delaware and Raritan Canal along the Stony Brook and sections of the Delaware River. In some places, steel sheet piling was subsequently added to these berms to reinforce them in a process known as “hardening.”
Barge: An open vessel that has no independent steering mechanism and is usually propelled by a tugboat. Barge was a term that was widely used in official reports and the media during the 19th century in reference to the vessels that operated in the Delaware and Raritan Canal. Canal historians and enthusiasts are quick to dispute the use of this term, and regard it as a misguided categorization. The purists argue that the correct name for such vessels should be “canalboat”; the argument being that if a vessel has a rudder, then it should be considered a “boat.” The captains of vessels on the Delaware and Raritan Canal referred to them as “boats.”
Boat: In the context of the canal, a vessel that is equipped with a steering mechanism and propelled either by mule or engine.
Canalboat: Any boat with an independent steering mechanism, propelled by mule or engine, using a canal for the transportation of cargo. Canalboats were usually of a symmetrical design, having provision for a rudder and tiller. While the typical canal had a canalboat specifically designed for its size and use, no one type of boat was used on the Delaware and Raritan Canal.
Chunker: A coal boat from Mauch Chunk, Pennsylvania (now known as Jim Thorpe) on the Lehigh Canal.
Hinge Boat: A two-section boat that could be separated in order to facilitate turning or unloading, which was developed for use on the steep inclined planes of the Morris Canal. Lehigh Coal and Navigation Company boats (the typical boat on the Delaware Canal and common on the Delaware and Raritan Canal) were hinge boats. Also known as a “Section Boat,” “Squeezer,” or “Lemon Squeezer.”
Light boat: A canalboat that is empty of cargo.
Packet: A passenger boat. Although advocates of the Delaware and Raritan Canal promoted its use for passenger travel, packets were never in great use on the canal. The close proximity of the railroad meant that few passengers chose the longer and slower journey by water.
Scow: A work boat, usually flat-bottomed, and used for maintenance and the hauling of construction materials.
Skuker: A coal boat from the Schuylkill Canal.
Stiff Boat: A boat which is not a hinge boat. Also known as a “Stiff.”
Tugboat: A tugboat or “towboat” is a strongly built steam or power vessel used for towing.
Swing Bridge: A drawbridge which swings open on a horizontal plane, rotating on a pivot, to permit passage of waterborne traffic.
A-Frame Bridge: A swing bridge, also called a “Shear-Leg Bridge,” was usually constructed of wood, with one end resting on a pivot on the berm bank. The other end is suspended by rods or cables from a large asymmetrical A-shaped wooden frame which was braced by another member, forming a large tripod.
King Post Bridge: A type of swing bridge, usually wooden, which utilized two vertical supporting members called king posts, to which diagonal tension members were attached, which in turn supported the weight of the unequally-long end of the bridge. The pivot mechanism for a king post bridge was constructed out into the canal, and the king posts were located over the pivot at the bridge's center of gravity, making for a stronger bridge and eliminating the need for the construction of supporting members on the bank.
Pivot Bridge: In the context of the Delaware and Raritan Canal, a pivot bridge was a type of swing bridge which rotated on a pivot mechanism mounted on a strong upright support. The pivot bridge was so balanced that supporting superstructures were not required. This type of bridge was made possible only by the introduction of the use of steel. Many of the bridges over the Delaware and Raritan Canal in the City of Trenton were converted to pivot bridges, and railroad bridges were often of this type. Five pivot bridges remain on the Delaware and Raritan Canal: the “workhouse” Railroad Bridge in Hopewell Township; the New Jersey Transit Princeton Branch Line (i.e. “Dinky”) Railroad Bridge in the Municipality of Princeton; the Main Street Bridge and railroad spur (now pedestrian) bridge in South Bound Brook Borough; and the Landing Lane Bridge in New Brunswick.
Drawbridge: In the context of the Delaware and Raritan Canal, a bridge that can be moved in whole or in part to admit traffic on the canal.
Bascule Bridge: A type of drawbridge having one or two counter-weighted cantilevered spans or bascules. Bascule bridges over the Delaware and Raritan Canal were once located at Southard and Perry Streets in City of Trenton, and on the Brunswick Pike (U.S. Route No. 1) in Lawrence Township.
Change bridge: A bridge that carried the towpath from one side of the canal to another. Change bridges were formerly on the Delaware and Raritan Canal at the Lambertville lock and at the summit of the canal in Trenton.
Farmer's Bridge: Also known as an “accommodation bridge,” a farmer’s bridge was a private access bridge constructed by the Canal Company when the canal crossed a farmer's property to enable the owner to reach the fields on the opposite side. The Canal Company bought up large parcels of land whenever possible in in order avoid constructing farmer's bridges.
Dam: A barrier constructed to obstruct the flow of a watercourse.
Crib Dam: A rubble- or stone-filled timber dam.
Wing Dam: A partial dam, often of crib construction, projecting from one or both banks of a waterway, used to raise the water level or to direct water, while permitting the passage of small craft. The wing dam located in the Delaware River at Raven Rock creates the pooling effect that provides water to the Delaware and Raritan Feeder Canal.
Cofferdam: A temporary dam erected to hold back water above a breach or to facilitate construction and maintenance work.
Control Gate: In general, a gate to regulate the flow of water.
Floodgate: A control gate built into the side of a canal used to release water or hold water within a canal to facilitate flood control.
Lock Gates: The control gates located at either end of a lock.
Mitre Gate: One of a pair of vertical hinged lock gates, the free ends of which were mitered and constructed so that when closed the gates remained at an angle, forming a V-shape. Mitre gates open upstream, and are kept closed by the pressure of· the water.
Heelpost: The vertical member to which the gate is hinged and about which the gate pivots. The post is held at the top by a collar and fits into a hollow or quoin in the lock wall in which it partially revolves.
Balance Beam Gate: A mitre gate that is usually equipped with a long, heavy, projecting beam or gate lever used to open it. The beam counterbalances the weight of the gate, and when pushed against, causes the gate to open or close. Corrugated runways were built under the balance beams to give the operator better traction.
Drop Gate: A lock gate that is hinged at the bottom and which opens by dropping to the floor of the canal. It is raised and lowered by a chain and wheel mechanism (windlass) and water pressure. Also known as a fall gate.
Guard Gate: A miter gate, similar to one found in a lock, but with only one set of gates. Guard gates were used to isolate water levels in case of breaks in the canal or maintenance. Guard gates were found at Demott Lane in Franklin Township and at Lower Ferry Road in Ewing Township.
Wickets or Paddle Gates: Small gates or paddles located at the bottom of mitre and drop gates through which the lock chamber is emptied or filled. These gates usually pivot on a center hinge attached to a rod and wheel mechanism for their control.
Sluice Gate: A vertically sliding gate used to control the flow of water. Operated by a chain and wheel mechanism (windlass), replaced today by valve and grooved wheel mechanisms.
Locks, Levels & Lifts:
Lock or Lift Lock: An enclosure or chamber with gates at each end that allows a boat to move from one level of water to another. A boat proceeding downstream enters the lock through the upstream gate, which then is closed to prevent more water from entering the lock. The water level in the lock chamber is slowly reduced by allowing the water to flow out through wickets in the downstream gate. When the water level in the lock equals that of the level downstream, the downstream gate is opened, allowing the boat to continue. The procedure is reversed for boats travelling upstream. The analogy of a staircase explains the operation of a lift lock canal: the stair risers represent the locks, while the treads the lengths of canal between locks.
The Delaware and Raritan Canal originally had 15 lift locks: one located on the feeder at Lambertville, 7 between Bordentown and Trenton (numbered 1 through 7) and seven between Trenton and New Brunswick (numbered 8 through 14) on the main canal. The double outlet lock at New Brunswick (Lock No. 14) accommodated the heavy traffic going to the factories in New Brunswick.
The lock walls on the Delaware and Raritan Canal were made of cut-face stone (known as Ashlar) and laid with hydraulic cement, a cement composed of an impure limestone with special properties that allowed it to harden under water. The Delaware and Raritan Canal was one of the first important uses of this material, introduced into this country by Canvass White on the Erie Canal. The original stone lock at Bordentown sank early in the canal’s history and was replaced very early with a rubble-filled wooden lock. The walls and ends of all locks were covered with wood cribbing to protect both locks and boats.
Locking through: The act of travelling through a lock.
Locking out: The act of travelling through an outlet lock.
Level or Open Water: The section of water between locks. The longest level on the main portion of the Delaware and Raritan Canal was from the State Street Lock in the City of Trenton to the Kingston Lock, a distance of approximately 13.75 miles. The shortest level was between Lock No. 3 and Lock No. 4 in the City of Trenton (approximately 0.25 mile).
Lift: The difference between the water level upstream and downstream of a lock. The highest lifts on the Delaware and Raritan Canal were at Lock No. 4 in the City of Trenton (12.4 feet, after it was combined with Lock No. 3) and the so-called “Deep Lock” No. 13 in New Brunswick (12.2 feet).
Outlet Lock: A lock that permits the passage of boats between a canal and a river or other body of water. The outlet lock accommodates changes in river level or tide but is generally not a true lift lock. The Delaware and Raritan Canal had outlet locks in Lambertville and New Brunswick. Lock No. 1 at Bordentown was a true lift lock, which also functioned as an outlet lock to the Delaware River.
Intake Lock: A guard lock at the intake or entrance of a canal. The lock at Bull’s Island was an intake lock for the Delaware and Raritan Canal.
Guard Lock: Similar to a lift lock in construction and used to guard the canal from changing bodies of water. Guard locks existed on the Delaware and Raritan Canal at Bulls Island and Prallsville Mills.
Double Lock: A pair of locks, generally to handle more traffic. The Delaware and Raritan Canal featured a double lock at New Brunswick.
Weigh Lock: A lock that was used to weigh canalboats, generally for the purpose of assessing tolls. The variety of vessels and cargoes made weigh locks impractical on the Delaware and Raritan Canal, where depth gauges were used instead.
Flight of locks: Three or more lift locks constructed in succession in order to accommodate a significant change in level. The natural topography made flights of locks unnecessary on the Delaware and Raritan Canal. The five locks on the Erie Canal at Lockport, New York, is an example of a flight of locks.
Inclined plane: An inclined plane consists of high inclines or hills of dry land laid with tracks upon which canalboats were transported in wheeled wooden carts, or cradles, pulled by cables between upper and lower canal levels. These planes were powered by water falling from the higher level; the water wheel mechanisms used originally were later replaced by turbines. Inclined planes were used at points of high elevation change where a flight of locks would have been impractical. The natural topography made inclined planes on the Delaware and Raritan Canal unnecessary. The Morris Canal, which had to master a rise and fall of 1,674 feet, required 23 inclined planes along its length.
Towpath: The major path along a canal, used by the mules and their drivers in towing canalboats.
Berm Path: Also known as the “Heel Path,” this is the path located on the opposite side from the towpath, not always continuous, used primarily for maintenance activities.
Multiuse Trail: The modern term used by the Delaware and Raritan Canal Commission and Division of Parks and Forestry to describe the recreational path in the Delaware and Raritan Canal State Park, which can be located on the former towpath, upon an abandoned railroad right-of-way, or on the former berm path.
Bridgetender: A Canal Company employee who was assigned to operate a swing bridge.
Level walker: A Canal Company employee who was assigned to walk the towpath and inspect for signs of leakage or failure, often caused by muskrats and other burrowing animals.
Locktender: The Canal Company employee assigned to operate a lock. Also Lockkeeper.
Ratter: A trapper hired by the Canal Company and paid daily wages to trap muskrats within his designated section of the canal. The ratter was permitted to keep the pelt (worth about 18 cents) and was paid a bounty of 15 cents for each tail. Fortunately for today’s rodents, muskrat damage to the canal is now addressed through non-lethal methods.
Skinner: A mule driver.
Tiller shark: A name for a canalboat operator.
The goal of the following information panel is to provide a brief explanation of the major structures of the Delaware and Raritan and how they functioned. It also demonstrates that construction of the canal required sophisticated engineering and skilled labor and was much more complicated than digging a very long ditch.
To avoid disrupting the natural drainage pattern of central New Jersey, most streams passed under the canal in arched culverts of hand-laid stone. These culverts have been carefully maintained by the New Jersey Water Supply Authority and are still in place today.
Instead of following the slope of the land a canal periodically takes vertical steps between levels of flat water. These steps are made at locks. The Delaware and Raritan Canal locks were stone or wooden chambers fitted with watertight gates at each end. Seven locks allowed boats to climb 70 feet from Bordentown to the summit at Trenton. Seven more locks accompanied the descent from the Trenton summit to sea level at New Brunswick.
Spillways were built at intervals along the entire length of the canal to prevent high water levels from eroding the banks. In some cases, a spillway is simply a place where the towpath is armored with stone and lowered to match the desired water level. Elsewhere, boxes were built next to the canal bank to collect excess water and direct it to pipes that went under to towpath, sending the water to a nearby stream.
About 50 bridges were built over the Delaware and Raritan Canal. Originally most of these were "A" frame bridges that swung to the side to allow boats to pass. A large framework -- shaped like the letter "A" -- was built at one end and supported the bridge with a network of cables. With the advent of the automobile in the early 20th century, the A frame bridges were replaced with were replaced by shorter “king post” swing bridges. Eventually all but a few swing bridges were replaced by the fixed span bridges.
Bridge- and Lock-tender Houses
The Joint Companies that operated the canal also built houses for the people who were responsible for opening the canal bridges and the operation of the locks. Many of these structures remain standing today, and some are open to the public.