Bolometer to Boric acid.

Bolometer. (Elec.) A thennal balance. (Phys.) A very sensitive instrument for measuring minute quantities of heat energy by. changes of electrical resistance.
Bolster. (Arch.) The lateral part of the volute of an Ionic capital; Ii cross­piece on an arch centering, running from rib to rib; the bearing place of a truss bridge upon a pier; a cap or top piece on a post to lengthen the bearing of a beam, etc, (Shopwk.) A block sometimes called the "die block." in which a punch-press die is held. It is attached to the head by bolts at either end.
Bolster. (Verb) To bolster up. To strengthen a support. (Noun) In general, a block or support; also a long pillow.
Bolt. (Mech.) A fastening; commonly a piece of metal with head and threaded body for the reception of a nut. (Woodwkg.) A block of tim­ber to be cut into pieces, as for stair treads or shingles.
Bolt cutter or bolt shear. Usually, hand-operated shears for cutting bolts, links of chain, etc.
Boltzmann's constant. Given by k = RIN= 1.38 X 10-23 JK-' where k = ideal gas constant and .N = Avogadro constant.
. Bomb. A projectile exploded by means of a fuse, by impact or othe~­wise, generally designed to be dropped by an aircraft.
Bombe. (Arch. and Furn.) Puffed, rounded, or bulged.
Bond (Masonry) Placing of bricks in a wall to tie together the face and backing. (Mech.) A binding agent, e.g., .material used to hold particles of abrasive together in a grinding wheel.

Bonded lining. (Auto. Mech.) The lining cemented to brake shoes or bands to eliminate the use of riv­ets.
Bond paper. (Papermkg.) Name originally given to paper made entirely from rags, animal sized; used for bonds and stock certifi­cates. Also hard-sized paper used for letter-heads, etc.
Bond stone. (Masonry) Stone run­ning through the thickness of a wall at right angles to its face, serving to bind it together along its thick­ness.
Bone black. (Chem.) Animal char­coal, obtained by the destructive distillation of bones. Used as a decolouring agent, filtering me­dium, sugar refiner, and as a paint pigment.
Bone china. (Ceram.) China made with an admixture of calcined bones (Phosphate of lime).
Bonnet. (Plumb.) A cover used to guide and enclose the tail end of a valve spindle.
Bookbinders wire. (Print.) Tinned openhearth steel wire, made in 18 to 30 gauge round shapes and 18 by 20- to 26- by 32-gauge flat shapes. Sold in 5-lb. spools or pa­per cones.
Bookbinding. Fastening bookd sec­tions and placing a cover over same.
Book paper. Coated or uncoated paper used for general printing purposes, as distinguished from wrapping, bond, ledger, and cover paper.
Boom. The movable arms of a derrick by which weights are lifted and shifted from one position to another.
Boom, microphone. A pole-like at­tachment that mounts atop a micro­phone stand and has a swivel or pivot point. The boom permits the mic to be raised higher or lower than the top of the stand, and to be placed closely to the desired instru­ment or performer.
Boost. (Aero.) To supply an engine with more air or mixture than it would normally induct at sea level.
Boost control, automatic. (Aero.) An automatic regulator of boost pres­sure.
Booster. (Elec. ) A generator tonnected in series with a circuit for ~he pur­
pose of increasing the voltage of that circuit. Generally used i~ con­nection with a system where a'stor­age battery carries part of the I~d. The booster increases the volta1\e
to a point where it becomes neces'.,sary to charge. the battery. '
Booster brake. (Auto. Mech.)An aux- 1\
iliary air chamber operated from the intake manifold vacuum, con­necting with regular brake pedal and increasing braking effects with less pedal pressure.
Booster coil. (Elec.) An induction coil using direct current to provide energy to the spark plugs of an (aircraft) engine when starting.
Booster magneto. (Aero.) An auxiliary magneto used for starting.
Booster pump. (Auto.) An auxiliary pump, built integral wit~ the fuel pump, providing vacuum to con­ tinue operation of the windshield wiper and similar devices when the vacuum of the intake manifold will not maintain tht:ir operation.
Booster rocket. (Aerosp.) A rocket motor which assists the normal pro­pulsion system of a rocket or other aerospace vehicle.
Boot. A covering serving as a protec­tion against dirt and weather.
Borax. (Chern.) (N~BP7) A white crystalline compound found native as "tineal," used as an antiseptic, for welding mixtures in iron and steel, for brazing gun metal and copper, and for softening water.
Borcher's metaL (Metal.) Alloy valu­able for its acid-resistant and cor­
rosion-resistant qualities. The prin­cipal ingredient is chromium.
Border. (Furn. )An outer-edge design of especially assembled veneer patterns. (Print.) Any line or orna­ mentation enclosing printing.
Bore. The internal diameter of a pipe, cylinder, or hole for shafting, whether it be rough or machined. (Mech. Drg.) Indicates that hole is. to be finished by boring.
Boric acid. (Chern.) A colourless crystalline compound (H3B03), made by treating borax with an acid; used in medicines and as a preserVative. (Cerarn.) Used in all finer qqality. gla&s and in most glazes and enamels as a flux.

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