Practical Mechanics for Boys Part 26

Parallel. Lines or sides at equal distance from each other from end to end.

Paraffine. A light-colored substance, produced from refined petroleum.

Perimeter. The outer margin of a wheel; the bounding line of any figure of two dimensions.

Periphery. The outer side of a wheel.

Peen. The nailing end of a hammer.

Persistence. That quality of all matter to continue on in its present condition.

Perpendicular. A line drawn at right angles to another.

Perpetual. Without end.

Perspective. A view of an object which takes in all parts at one side.

Physically. Pertaining to the body.

Phonautograph. An apparatus for recording sound.

Phonograph. An apparatus for taking and sending forth sound vibration.

Phenomena. Any occurrence in nature out of the ordinary.

Pitman. The rod or bar which connects the piston and crank.

Pivot. A point or bar on which anything turns.

Pinion. A small toothed wheel.

Pitch. The number of vibrations. The term used to give the number of teeth in a wheel.

Pitch diameter. The point from which the measurements are made in determining the pitch.

Pivoted. A bar, lever, or other mechanical element, arranged to turn on or about a point.

Plastic. A substance in such a state that it may be kneaded or worked.

Planer. A large tool designed to cut or face off wood or metal.

Porosity. The quality in all substances to have interstices, or points of separation, between the molecules.

Potential. The power.

Properties. The qualities possessed by all elements.

Projecting. The throwing forward. The sending out.

Promulgated. Put forth; enunciated.

Protractor. A mechanic's and draughtsman's tool by means of which angles may be formed.

Promote. To carry forward in a systematic way.

Precision. Work done with care; observing correct measurements.

p.r.o.ny brake. A machine for determining horse power.

Punch. A small tool to be struck by a hammer in order to make an impression or indentation.

Quadrant. One-fourth of a circle.

Quadrant plate. A plate on which are placed lines and numbers indicating degrees.

Quadruplex. A term to designate that system of telegraphy in which four messages are sent over a single wire at the same time.

Ratchet. A wheel having teeth at certain intervals to catch the end of a pawl or finger.

Ratchet brace. A tool to hold a drill, having a reversible ratchet wheel.

Rasp cut. A cut of a file which is rough, not smooth.

Rake. The angle or inclination of the upper surface of the cutting tool of a lathe.

Reverse. To turn about; in the opposite direction.

Reciprocating. To go back and forth.

Revolve. To move in an orbit or circle, as a merry-go-round.

Reciprocity. To give back in like measure.

Reflection. The throwing back from a surface.

Resonance. The quality of vibration which adds to the original movement, and aids in perpetuating the sound.

Refraction. The quality of light which causes it to bend in pa.s.sing through different substances.

Reducing. Bringing it down to a smaller compa.s.s.

Rectilinear. A straight line.

Retort. A furnace of refractory material to take high heat.

Reamer. A tool designed to enlarge or to smooth out holes.

Regulation. To do things in an orderly way; a system which sets forth certain requirements.