Air space to Allotropic.

Air space to Aliasing
it is worthless for many of the purposes for w.hich water-slaked lime is used.
Air space. (Elec.) The open space in a dynamo or motor between the polar faces of the field magnet and the surface of the armature.
Air speed. (Aero.) The speed of an
aircraft relative to the air.
Air-speed head. (Aero.) An instru­ment which, in combination with a gauge, is used to measure the speed of an aircraft relative to the air. It usually consists of a pitot­static tube or a pitot-venturi tube.
Air-speed indicator. (Aero.) An in­strument for indicating the speed of an airplane relative to the air.
~ir spirng. (Auto. Mech.) Another name for the most efficient type of shock absorber. A plunger operates in a cylinder which contains oil and air. .
Airtight. So constructed or sealed as to prevent any inlet or outlet of air.
Air-to-air. Operating between flying aircraft or directed from one flying aircraft to antoher.
Air-to-surface. Operating or directed from a flying aircraft to the surface of the earth.
Airway beacon. (Aero.) An estab- .
lished air-route.
Airway beacon. (Aero.) A beacon light of high candle power, other than an airport or landmark bea­con, locatcd on or near an airway for the purpose of indicating the location of the airway.
Airworthiness. (Aero.) The quality of an aircraft denoting its fitness and safety for operation in the air under normal flying conditions.
Aisle. (Arch.) A passageway, as in a church or assembly room, by which the pews or seats may be reached.
Alabaster. (Min.) A white or deli­cately tinted fine-grained gyp­sum.
Albertite. (Mill.) A jet-black, brit­tle, natural asphalt found in Nova Scotia. Yields mineral oils and coke.
Album. A book for holding photo­graphs or the like. A blank book for holding stamps, autographs, etc.
Alchemy. (Chern.) Chemistry as it was practiced in the Middle Ages. Its purpose was largely to dis­cover the transmutation of metals and the universal cure of diseases.
Alcohol. (Chern.) C2HsOH. Ethyl hydroxide, made from grain. Not to be confused with methyl hy­droxide or methanol.
Alcohol thermometer. A thermo­meter based on the expansion of alcohol in glass as a function of temperature.
Alcove. (Arch.) Any large recess in a room, usually separated by an arch.
Aldehyde. (Chern.) The first oxida­tion product of a primary alco­hol. CH3CHO.
Algebraic symbols. (Math.) Con­ventional signs, letters, brackets, etc., by which certain processes and calculations in mathematics are indicated.
Aliasing. An undesirable distortion component that can arise in dig­ital audio equipment when the

input signal's frequency exceeds one-half of the digital circuitry's sampling rate.
Align. (Auto.) To bring parts into proper position in relation to one. another.
Alignment. (Madl.) Linear accuracy, uniformity, or coincidence of the centers of a lathe. Also applied to the axial continuity of shafting and shaft bearings; a straight line of adjustment through two or more points.
Alignment protractor. Device for measuring or indicating errors in material alignment of a tone arm. Locates on turntable centre spin­dle, cartridge stylus fitting in a small hole.
Alignmnt tape. A special tape record­ing for use in alignment and cali­bration of tape recordings, and containing test tones as specified frequencies .usually 30Hz, 50Hz, 100Hz, 250Hz, 500Hz, 800Hz, and
1kHz, 2.5kHz, 5kHz, 7.5kHz, . 10kHz, 12kHz, and 15kHz. Alignment tapes are generally recorded I one-at-a-time and held to precision tolerances.
Alive. (Elec.) A term applied to a car­rying circuit, or to two adjacent contacts of different potential. (Print.) Standing type matter not to be distributed.
Alizarin. A yello~ to orange crystal­line colouring compound used to dye cotton, wool, and silks.
Alkali. (Chern.) A strong base. A base is a substal\ce which produces hydroxyL Ions when dissolved in water.

Alkanet. A dye-producing plant, na­tive of the Mediterranean region, Hungary, and western Asia, yield­ing a red colouring malter.
Alkyd resins. (Chern. Plast.) The name is derived from the first two letters of the word alcohol and "cid" of the word acid. This type of resin is use ~ principally for lac­quers, paints, and metal finishes.
Allen screws. (Mach.) Cap screws and setscrews having hexagonal socket in the head. Such screws are adjusted by means of a hex­agonal key.
All-geared drive. (Mach.) The transmission of power for feeds and speeds on a machine by means of gears instead of by belts and pulleys.
Alligation. (Arith.) The method or rule for finding the relation be­tween the prices of the ingredi­ents in a mixture, their propor­tions, and t~e price of the mix­ture.
Alligatoring. (Paint and Lacquer) Cracks in the surface layer only, which widen due to contraction, caused by a sudden change in temperature, lack of binder, not sufficient drying time between
coats, poor penetration, or apply­ing a hard film over a soft under­coat.
Alligator wrench. (Plumb.) A wrench with toothed V-shaped jaws fixed in position.
Allotropic. (Chem.) Different form of the same substance, e.g., dia­mond and coal as forms of carbon.