{ Space bar or key }. (Mach.) A bar or key, in a typewriter or typesetting machine, used for spacing between letters.
Spad (?), n. (Mining) A nail one or two inches long, of iron, brass, tin, or tinner iron, with a hole through the flattened head, used to mark stations in underground surveying.
Spark, v. i. (Elec.) To produce, or give off, sparks, as a dynamo at the commutator when revolving under the collecting brushes.
Spark coil. (Elec.) (a) An induction coil, esp. of an internal-combustion engine, wireless telegraph apparatus, etc. (b) A self- induction coil used to increase the spark in an electric gas-lighting apparatus.
Spark gap. (Elec.) The space filled with air or other dielectric between high potential terminals (as of an electrostatic machine, induction coil, or condenser), through which the discharge passes; the air gap of a jump spark.
Spark plug. In internal-combustion engines with electric ignition, a plug, screwed into the cylinder head, having through it an insulated wire which is connected with the induction coil or magneto circuit on the outside, and forms, with another terminal on the base of the plug, a spark gap inside the cylinder.