Allover pattern. (Art.) A pattern repeated over an entire surface.
Allowance. (Mach.) The minimum clearance or maximum interference .intentionally permitted between mating parts.
Allowed band. Range of energy levels permitted to electrons in a molecule or crystal. These may be vacant or occupied.
Alloy. (Metal.) White metal. Babbitt metal. (MetaLwk.) A homogeneous combination of two or more metals, usually a fine and a baser metal. (PLast.) A blend of synthetic resins.
Alloy steel. (MetaLwk.) A steel which is alloyed with one or more of the following metals: manganese, nickel, tungsten, molybdenum, vanadium and chromium. These alloy steels are strong, tough, and hard.
All rowlock wall. (Masonry) A wall built with two courses entirely of stretchers on edge alternating with one course of headers on edge.
Almandite. (MineraL.) A variety of mineral garnet, used for abrasive
coating on paper and cloth.
Almery. (Arch.) Same as ambry. Alnic. (MetaL.) An alloy, a combina
tion of aluminium, nickel, and cobalt, used to make small permanent magnets. This combination gives the alloy its high retentivity.
Alpha. The first letter of the Greek alphabet (A) (ex). (Chern.) A form which is combined. Distinguishing one of two or more isomers or modificalions.
Alpha particle. (Chern. and Phys.) A high velocity electrically c!larged particle thrown off by many radio
active materials; has two neutrons and two protons.
Alpha rays. (Chern. and Phys.) One of the three types of rays emitted. by radioactive substances.
Altar. (Arch.) In present-day use, commonly applied to the communion table in churches. Originally, a raised platform on which sacrifices or offerings were made to the gods.
Alter-nating current or a.c. (ELec.) An electric current which reverses in direction at rapid, regular intervals, usually 120 times per second.
Alternating-current arc. (ELec.) An arc produced by an alternating current. In such an arc the carbons assume tapered points instead of cratering, which permits a more horizontal spreading of the light.
Alternating-current arc welding. An arc-welding process wherein the supply at the arc is alternating current.
Alternating-current motor. (ELec.) An electric motor of either single or polyphase type operated by an alternating current.
Alternating-current transformer. (ELec.) A device used to raise or lower the voltage of an alternating
circuit. It consists of an induction.
coil having a primary and secondary winding and a closed iron core.
Alternating-current transmission. (ELec.) The transmission of power by the use of alternating current.
Alternation. (ELec.) The changes undergone by an alternating current
in rising from zero to maximum.
.positive pressure, faIling to zero, then rising to maximum negative
Aluminium stearate. (Paint and Lacquer) Used in the manufacture of lacquers to produce a flat finish.
Alum leather. Leather tanned by the use of alum.
Amalgam. (Min.) An alloy or union of mercury with one or more metals.
Amalgamation. (Elec.) The application of a coating of mercury to the zinc plate of a voltaic cell, thereby forming an alloy which prevents the local action liable to arise form impurities in the zinc.
Amber. (Elec.) A yellowish or reddish brown translucent fossil resin which becomes electrified through friction when rubbed against another object.
Ambo. (Arch:) In early Christian churches, a raised pulpit-like platform stand, or desk, where parts of the service were read or chanted.
Amboina; amboyna. (Wood) An East I.ndian tree which produces what is commonly considered the most beautiful and most expensive of cabinet woods and veneers.
Ambroin. An insulating material made from fossil copal and silicates. It is strong, heat resisitant, and nonhygroscopic. It is used for molded insulations, and is cheaper than ebonite.
Ambry. (Arch.) A closet near the altar for sacred vessels. A cupboard.
American bond. (Masonry) Same as common bond.This bond is in very general use as it is quickly laid and is as strong as other bonds. Every fifth or sixth course consists of headers, while the other courses consist of stretchers.
American screw gauge. (Metalwk.) A standard gauge for checking the diameter of wood screws and
machine screws. .
American Standard Pipe Threads. (Formerly known as Briggs Pipe Thread Standard.) Is the thread used on wrought iron or steel, steam, gas and water pipes.
Amethyst. (Min.) Quartz with a clear purple or violet colour. A precious stone.
Amino. (Plast.) Combining form in name of chemical compound indicating presence of NH2 group, derived from ammonia.
Aminoplast. (Chern. Plas!.) General term for synthetic resins from
|
