=Paraffine.= A residuum of petroleum oil, valuable as an insulating medium in electrical work. A hydro-carbon composition of the highest resistance known. It is extensively used in condensers and other electrical apparatus as a dielectric and insulator. =Parallel Distribution.= A distributing system for electricity wherein the receptive contrivances are adjusted between every two of a number of parallel conductors running to the limits of the system. When two or more conductors connect two mains of comparatively large size and low resistance, they are said to be in parallel or in multiple. This order is easily pictured by imagining the mains to be the sides of a ladder and the conductors the rungs. In the latter the lamps are placed. It follows that the current flows from one main to the other through the conductors and lamps. =Paramagnetic.= Substances which have magnetic properties, or those which are attracted by magnetic bodies. A paramagnetic substance has high multiplying power for lines of force, therefore a bar of iron which is a paramagnetic substance of the highest quality becomes magnetic when placed within a circle of electric lines of force. The first example of paramagnetic substance brought to the attention of man was the lodestone, from which the ancient mariners fashioned their crude compass needles. =P-C.= An abbreviation for porous cup. =Pear Push.= A push-button enclosed in a handle having the shape of a pear. It is generally attached to the end of a flexible wire cord. =Periodic Current.= (_See_ Current, Periodic.) =Permanency, Electric.= The power of conductors to retain their conductivity unaffected by the lapse of time. =Permanent Magnet.= (_See_ Magnet, Permanent.) =Phase.= One complete oscillation. The interval elapsing from the time a particle moves through the middle point of its course to the instant when the phase is to be stated. Simple harmonic motion. Oscillation. =’Phone.= An abbreviation for the word Telephone. =Phonograph.= An apparatus for reproducing sound. It is vibratory and not electric in its action, except that the mechanism may be driven by electricity. It consists of a rotating cylinder of a waxlike material and a glass diaphragm carrying a needle-point that lightly touches the surface of the waxen cylinder. If the diaphragm is agitated the needle vibrates, making indentations in the surface of the wax. If the needle is set back and the cylinder rotated so as to carry the point over the indentations, the sound is given back through the vibration of the diaphragm. =Pickle.= An acid solution used to cleanse metallic surfaces preparatory to electro-plating. =Pilot Wires.= Wires brought from distant parts of electric light and power mains, and leading to voltmeters at a central station. Through their agency the potential energy of every part of the system may be measured.