=Crater.= The depression that forms in the positive carbon of a voltaic-arc. =Creeping.= A phenomena met with in solution batteries. The electrolyte creeps up the sides of the containing jar and evaporates, leaving a deposit of salts. Still more solution creeps up through the salts until it gets clear to the top and runs over. To prevent this the tops of the jars should be brushed with hot paraffine for a distance of two inches from the upper edge. The salts will not form on paraffine. Oil is sometimes poured on the top of the battery solution, but this affects the elements if it touches them, and makes their surfaces non-conducting. =Crucible, Electric.= A crucible for melting refractory substances, or for reducing ores by means of the electric arc produced within it. Probably the result obtained is due more to current incandescence than to the action of the arc. =Crystallization, Electric.= Under proper conditions many substances and liquids take a crystalline form. When such action is brought about by means of electricity the term electric crystallization may be applied to the phenomenon. A solution of nitrate of silver, when decomposed by a current, will give crystals of metallic silver. A solution of common salt or brine, when electrically decomposed, will produce sodium and chlorine. The sodium appears at the leading-out electrode and readily unites with carbonic-acid gas, which is injected into the apparatus. The result of the combination is carbonate of soda, one of the most important products of the alkali industry. =Current, Alternating.= A current flowing alternately in opposite directions. It is a succession of currents, each of short duration and of direction opposite to that of its predecessor. Abbreviation, A-C. =Current, Amperage.= The volume of electricity passing through any circuit per second, the flow being uniform. =Current, Constant.= An unvarying current. A constant-current system is one in which the current is uniformly maintained--for example, in electric light, power, and heat plants. =Current, Continuous.= A current of one direction only, or the reverse of an alternating current. =Current, Direct.= A current of unvarying direction, as distinguished from the alternating. Abbreviation, D-C. =Current Distribution, Uniform.= A steady current; a current whose density in a conductor is always the same at all points. =Current, Induced.= A current caused by electro-dynamic induction. =Current, Low Potential.= A current of low pressure. A term applied to low electro-motive force. =Current, Make-and-break.= A current which is continually broken or interrupted and started again. The term is applied only where the interruptions occur in rapid succession, as in the action of an induction-coil or pole-changer. The alternating current. =Current-meter.= An apparatus for indicating the strength of a current, such as an ammeter. =Current, Oscillating.= A current periodically alternating.