96 



Galvanometer Telescope and Scale. A device for observing 

 deflections of mirror galvanometers or similar instruments. 

 The apparatus is arranged so that the image of the scale 

 formed by reflection in the galvanometer mirror can be 

 seen through the telescope, and the magnitude of the 

 deflection is deduced from the change in the reading of the 

 scale which corresponds to the cross-line of the telescope. 

 [1, 3, 4, 10, 16, 19.] 



Galvanoscope. An instrument for detecting the presence of elec- 

 trical currents, especially such as are of feeble intensity. [16.] 



Gal vano thermometer. An instrument for measuring the beating 

 effect of a galvanic current. 



Gas Analysis Apparatus. Apparatus for the chemical analysis 

 of gas and gaseous mixtures. The gases are passed through 

 various vessels and absorbed by suitable agents or exploded 

 by an electiic spavk. Many forms are made to suit individual 

 processes and requirements. [13.} 



Gas Analysis Apparatus. [17.] 



Gas Gauge. See Gauge. [4, 5, 6, 13, 15, 17, 21, 26.] 



Gas-Leak Indicator. See Indicator. [4, 5, 17, 21.] 



Gasophaner. An indicator of the presence of poisonous gases. 

 [21.] 



Gas Pressure Meter. See Meter. [17.] 



Gas Purity Meter. See Meter. [4.] 



Gas Regulator, Reichert's. A mercury gas regulator for regu- 

 lating the temperature of ovens, incubators, etc. [2, 4.] 



GasWorks' Thermometer. See Thermometer. [4, 5, 13, 15, 16, 17, 

 21.] 



Gasoscope. An apparatus for detecting the presence of any 

 dangerous gas from a gas leak hi a coal mine or dwelling- 

 house. 



Gassiot's Cascade. See Cascade. 



Gauge, Bourdon Pressure or Vacuum. An instrument invented by 

 M. Bourdon of Paris, consisting of an elastic flattened tube 

 of metal bent to a circular form and communicating with 

 the steam, au* or other fluid under test. An increase of 

 pressure tends to straighten the tube, a decrease to make it 

 curve. One end of the Bourdon tube is fixed and the other 

 free to move. The movement is communicated to a pointer 

 which indicates, on a dial or on a chart, the amount of 

 pressure or vacuum. [4. 5, 6, 13, 15, 16, 17, 20, 21, 24, 25, 

 26, 27, 28.] 



Gauge, Bourdon Pressure, Duplex. A similar instrument to the 

 above, but provided with two Bourdon tubes and two pointers 

 so that two readings are obtained. The mean of the two 

 readings gives a more accurate figure than one reading alone, 

 and the instrument can thus be used as a standard. [15.] 



Gauge, Depth. An instrument for determining the depth of 

 water by means of the pressure it exerts. Sometimes called 

 a Hydro-Barometer (g.v.). See also Tide-Gauge. [15.] 



