6o 



Balance Electrometer. See Electrometer. [16.] 



Balance, Hydrostatic. A balance for weighing substances in 

 water to obtain their specific gravity. 



Balance, Joly's Specific Gravity. A spring balance; used for 

 the determination of specific gravities, in which the sub- 

 stance to be weighed is suspended from a vertical metal 

 spiral spring. 



Balance, Physical. Similar in type to the Chemical Balance, 

 but generally less sensitive and designed to carry heavier 

 loads. 



Balance, Spring. A form of balance in which the weight of the 

 body to be determined is measured by the extension or 

 compression of an elastic spring. 



Balance, Thermic. See Bolometer. 



Balance Thermometer. See Thermometer. [13, 20, 21.] 



Ballistic-Galvanometer. See Galvanometer. [4, 16, 19.] 



Ballistic-Pendulum. See Pendulum. [19.] 



Banana Thermometer. See Thermometer. 



Barmacrometer. An instrument for determining the height and 

 weight of a newborn infant. 



Bar-Magnet. A steel bar permanently magnetised. [2, 10, 13, 

 15, 16, 19, 21, 24, 27, 28.] 



Barograph. A form of aneroid barometer (q.v.) provided with a 

 clockwork-driven drum, pen and chart for recording auto- 

 matically, in the form of a curve, variations of atmospheric 

 pressure. [2, 3, 4, 5, 6, 9, 10, 13, 15, 16, 17, 20, 21, 24, 25, 

 26, 27, 28.] 



Barometer. An instrument for determining the weight or 

 pressure of the atmosphere and, indirectly, for measuring 

 heights (e.g. of mountains, etc.) above the earth's surface. 

 Made in two principal forms, the Aneroid and Mercury 

 Barometers. [2, 3, 5, 6, 9, 10, 13, 15, 16, 17, 20, 21, 24, 25, 

 26, 27, 28.] 



Barometer, Aneroid. A form of barometer without liquid. Its 

 action depends on the effect of the varying pressure of the 

 atmosphere on the elastic sides of a metal box, from which 

 the air has been exhausted. See also Barograph. [2, 3, 5, 

 6, 13, 15, 16, 17, 20, 21, 24, 25, 26, 26, 27, 28.] 



Barometer, Board of Trade Pattern. A mercurial barometer of 

 the type specified by the Board of Trade. [15.] 



Barometer, Boylean Mariotte. A portable mercury barometer in 

 which the atmospheric pressure is determined by a uniform 

 volume of air being admitted to the cistern and compressed 

 by the advance of the mercury to a fixed point. The total 

 length of the instrument is under 15 in. See also Sympieso- 

 meter. [13, 27, 28.] 



Barometer, Collie's. A portable mercury barometer provided 

 with a flexible rubber tube in place of the usual glass tube. 



Barometer, Dial or Wheel. A mercury barometer in which the 

 movement of the mercury is measured by means of a float 



