Perch to Phenol

Perch to Perpend

relation to the whole.
Perch. In stonework, a variable mea­sure, usually about 25 cu. ft.

Percussive welding. A resistance' welding process wherein a rela­tively intense discharge of elec­trical energy and the application of high pressure (usually a ham­mer blow) occur simultaneously or with the electrical discharge which occurs slightly before the application of the pressure or ham­mer blow.

Perfecting press. (Print.) A machine with two impression cylinders able to print both sides of a sheet at one time.

Perforating. (Print.) The punching of small holes in a sheet of paper to aid in separating it into parts.

Perforating machine. (Print.) A ma­chine for punching a row of small holes in paper to permit even sepa­ration of the parts; used in che~ks, bill-heads, etc.
Perforating rule. (Print.) A piece of rule put into a type form so the job may be printed and perfo­rated in one operation. .

Performance-type glider. (Aero.) A glider having a high degree of aerodynamic refinement and low minimum sinking speed.

Periodic arrangement. (Chern.) An arrangement of elements in the order of their increasing atomic numbers. As a result of this ar­rangement the elements fall into nine natural groups, the members of each resembling each other very strongly.

Peripheral speed. (Mach.) The speed, usually registered in feet per minute of the circumference of a part, as a wh'eel or a shaft. .

Periphery. (Math.) The circumfer­ence of a circle, ellipse, or simi­lar figure. - .­

Periscope. An instrument containing an arrangement of mirrors which permits the observer to see over intervening objects.

Peristyle. (Arch.) A system of col­umns encircling a building.

Permanent load. (Engin.) A load which is constant and unvarying; a dead load as the weight of the structure itself or a load imposed, or both taken together.

Permanent magnet. (Elec.) A piece of magnet steel which retains the acquired property of attracting other pieces of magnetic material after being under the influence of a magnetic field.

Permanent set. (Engin.) The amount of deflection from which a beam or structure is unable to return to its original form.

Permanganate. (Chern. and Wood Fin.) A dark purple salt of per­manganic acid (HMn04).

Permeability. (Elec.) The ratio of flux density to magnetizing force.

Permutation. (Math.) The arrange­ment of any determinate number of things or letters in all possible orders, one after another.

Perpend. (Masonry) A header brick extending through then all so that one end appears on each side of it.

Perpendieular to Phenol

Perpendicular. Meeting a given line or surface at right angles.

Perron. (Arch.) A staircase outside of a building, leading to the first floor.

Per-simmon. (Wood) Diospyros virginiana. Belongs to the ebony family. Does not grow large enough to be of great commercial value. Wood is yellowish, often streaked with black; hard and strong, and takes high polish. Used for brush backs, billiard cues, ~nd veneer.

Perspective. (Draw.) The art of sci­ence of representing on a plane surface objects as they actually appear to the eye.

Persuader. A common term for crow­bar, lever, or some such article used as a manual aid in moving heavy objects.

Pestle. An implement for grinding substances in a mortar. Pet cock. A drain cock which, when open, permits the reiease of gas, air, or liquid from the vessel to which it is attached.

Petrography. The study and classi­fication of rocks.

Petrol. British name for gasoline. The term is little used in the U.S.

Petroleum. (Chern.) A natural oil taken from the earth, used exten­sively for heating and as a motor fuel in distillates such as fuel oil, diesel fuel, gasoline, kerosene, benzine, etc.

Pew. (Arch.) One ofthe long benches used as seats in a church.

Pewter. (Metal) An alloy of tin, lead and antinomy, formerly much used for tableware.

Phaeton. (Auto.) An open type body with two cross seats. Has folding windshield and weatherproof top and side curtains.

Phantom drawing. (Draft.) Usually refers to some "dotted in" part added to a drawing to show the relation, method of connection, assembly, etc., of or to the project being drawn.

Pharmaceuticals. (Chern.) Drugs and similar chemicals sold through drugstores.

Phase. (Elec.) The time instant when the maximum, zero, or other rela­tive value is attained by an elec­tric wave.

Phase angle. (Elec.) The angle which expresses the phase relation in an alternating-current circuit.

Phase meter. (Elec.) A meter which indicates the frequency of the circuit to which it is attached. A frequency meter.

Phase modulation. Radio transmis­sion in which the carrier wave is modulated by changing its phase to transmit the amplitude and pitch of the signal.

Phenol. (Chern.,) A crystalline sub­stance (C6HP'H), a limited sup­ply of which is obtained from coal tar. Also produced synthetically by fusing sodium benzine sulphonate with caustic soda, and then neutralizing with hydrochlo­ric acid. Used also in the manu­facture of dyestuffs and pharma­ceutical products, antiseptics, etc.