Plug.
1. (Building.) A block of wood let into a wall of brick or masonry, to afford a hold for nails in fixing the interior finishing. [1749]
2. (Nautical.) a. A conical piece of wood used to stop the hawse-holes when the cables are unbent. b. A block to stop a hole made by a cannon-ball in a ship. c. A stopper for the hole in a boat-bottom.
3. (Steam-boiler.) A stopper of metal which is placed in a steam-boiler or a pipe in communication therewith, and which melts at a certain temperature, so as to establish an exit from the boiler when the temperature and consequent pressure become dangerous. See fusible plug; high-pressure alarm.
4. (Die-sinking.) A cylindrical piece of soft steel, whose end is turned to fit into a matrix. The indented (intaglio) design of the matrix is transferred to the end of the plug when the two are pressed forcibly together. The plug having the design in relief (camco) is then hardened and becomes a punch, which is used to impress the faces of dies for coining. See matrix; die.
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| Fire-plug. |
5. (Stone-working.) The plugs are inverted wedges with round backs placed in a hole which has been jumped in a rock; a feather or tapered wedge, being driven between the plugs, rends the rock. (a, Fig. 3834.)
6. (Masonry.) A dowel or cramp.
7. (Railway.) A wedgepin driven between a rail and its chair.
8. (Hydraulics.) A branch pipe b leading from the main below the pavement and terminating at a point readily reached for the attachment of hose. This pipe is closed by a cap or plug, which is removed by a spanner when the hose is to be attached by its coupling to the thread on the pipe. A stopcock on the branch pipe is reached by a turn-key introduced at an opening in the pavement. Fire-plugs were first laid down in London in 1710. London was first supplied with water by leaden pipes in 1237. The water was brought from the Springs of Tyburn, a district long since included in the city, — not the city proper, but the metropolis as outsiders understand it. In 1613 Sir Hugh Middleton finished his aqueduct from Ware to London. This is yet called “the New River,” and discharges into a reservoir at Islington, a northern suburb of London. The water was distributed by wooden mains and lead-pipe branches. Water-carriers still plied their trade in the reign of Queen Anne, supplying households from the public pumps, which were and are yet numerous, and yield abundant and excellent water.
9. (Ordnance.) The wooden stopper in the vent of a petard. 10. a. A small tompion in the muzzle of a musket-barrel. b. The nipple of a gun.
11. (Dentistry.) A filling for a carious tooth.
