| Definition of Terms
Ashlar - square cut stone (see also "dressed stone").
Breastwork - a foundation under the upper end of a lock, making up the difference in height between the bottom of the lock and the bottom of the upper channel.
Clay Puddle - clay mixed with coarse sand or fine gravel, wetted and then chopped, beaten and kneaded into a consolidated mass, about two-thirds of its original volume. If kept in an area where it remains wet (i.e. below the water table) it remains completely watertight.
Coffer Dam - a temporary dam place in front of, or around an area to be worked, to allow it to be pumped dry.
Crab - a winch with a hand crank used to move heavy objects (lock gates, valves). Often referred to as "crabs and chains" since chains are used to attach the crab to the object to be moved.
Dressed stone - stone that has been finished, shaped.
Grout - a thin mortar that can flow, or be injected under pressure, to seal up cracks.
Guard – the excess height of lock walls over the normal water level needed to protect the lock from being overflowed by spring flood waters.
Guard Lock – a non-lift lock placed in advance (upstream) of the lift locks to protect them from damage by spring flood waters and debris.
Inverted Arch - a shallow arch with concave side up (like the bottom of a bathtub). Usually made of masonry (stone)
Key Work - shaped stones fitted together, usually the back face of a dam.
Lock - a watertight basin with gates and valves at both ends that allow water to be let in, or let out, to raise or lower a vessel from one water level to another.
Lockmaster – the overseer of a lock. Responsible for the operation of a lockstation. In the early days, this meant that the lockmaster had to be on-call 24 hours a day. Many of the first lockmasters were members of the Royal Sappers and Miners who helped to build the locks.
Malaria - a disease caused by a parasite, characterized by recurring fever and chills. Present throughout North America in the 19th century. Transmitted by a particular type of mosquito.
Masonry - stonework (or the work of a mason).
Plug and Feathers - a simple device used to help split rock. A series of holes would be drilled about six inches (15 cm) deep into the rock and then the feathers, two pieces of curved metal, would be inserted in each hole. A wooden plug, a tapered cylinder (narrower at the bottom than the top - like a wedge) would be inserted between the feathers. The plugs would then be tapped with a sledgehammer, progressing along the line of holes. The plugs would force the feathers apart, putting a splitting force into the rock, eventually causing the rock to split along the drilled line.
Sappers and Miners - these are soldiers of the Royal Engineers - men experienced in excavations (saps are trenches) and construction.
Sill - the flat "floor" at both ends of a lock on which the base of the gates rest.
Sluice - a channel way or trough through which water can flow in a controlled manner.
Sluiceway - see "Sluice."
Snie - a flood channel (usually dry). A snie would often take the form of a gully running close to the main channel of the river. These were often located at rapids, formed by spring floods seeking a way around the rapids and carving a new channel adjacent to the rapids.
Stop Log - squared timber that can be dropped into slots at either end of a lock, or in a weir, to stop the flow of water.
Wing Walls - the rounded walls at either end of a lock
Lake Fever - early name for malaria - thought at the time to be caused by 'bad air" (hence "mal" "aria") emanating from shallow lakes, swamps and bogs. See malaria.
Swamp Fever - see "Lake Fever."
Waste Weir - see weir.
Weir - a water control dam, a structure with a sluiceway (or several sluiceways) that allows the upstream water level to be controlled.
Wing Wall - the curved wall at the end of a lock, beyond the gates, protecting the lock chamber from being undermined by water.