95 



deflections are measured by the movements over the scale 

 of the beam of light reflected from the galvanometer mirror. 

 [4, 16, 19,] 



Galvanometer Lenses. Lenses used with reflecting instruments, 

 such as mirror galvanometers, to aid in obtaining a beam 

 of reflected light, by which the deflections may be observed. 

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



Galvanometer, Mirror. A sensitive galvanometer in which the 

 current deflects a mirror attached to the moving magnet 

 or coil, measurement being made by observing the move- 

 ment of a beam of light (reflected from the mirror) over a 

 graduated scale. [4, 16, 19.] 



Galvanometer Mirrors. Small light mirrors which can be 

 attached to the suspensions of galvanometers or similar 

 instruments in order to give a beam of reflected light which 

 will move as the instrument is deflected, and so magnify 

 the deflections for convenience of observation. [3, 4, 10, 

 12, 16, 19, 21, 23.] 



Galvanometer, Paschen. An improved form of Thomson Gal- 

 vanometer of extremely high sensitivity. The moving 

 system consists of two groups, each composed of 13 very 

 light magnets, arranged alternately on opposite sides of a 

 fine glass stem. 



Galvanometer, Pivoted Moving Coil. An instrument for use 

 under rough conditions, or where a portable instrument is 

 required. The moving coil, instead of being suspended in 

 the magnetic field, is supported on jewelled pivots. The 

 deflections are generally read by means of a pointer swinging 

 over a scale instead of by a mirror. [4, 10, 16, 19.] 



Galvanometer, Recording. A galvanometer provided with a 

 recording arrangement so that the results are given on a 

 chart. [4, 16.] 



Galvanometer, Sine. A galvanometer in which the strength of 

 the current is measured by the sine of the angle through 

 which the coil has to be turned to be parallel to the deflected 

 needle. [19.] 



Galvanometer, Tangent. A galvanometer in which the strength 

 of the current is measured by the tangent of the angle of 

 deflection of the magnet. [19, 20, 24.] 



Galvanometer, Thomson. A moving magnet galvanometer in 

 which the moving system is formed of two groups, each con- 

 sisting of four small magnets. [4, 16, 19, 21.] 



Galvanometer, Thread Recorder. A recording galvanometer of 

 the moving coil type in which a pointer attached to the 

 moving coil is automatically depressed at regular intervals 

 on to an inked thiead which passes across the surface of a 

 revolving drum carrying a chart. The depression of the 

 pointer presses the inked thread against the chart and so 

 gives a record of the galvanometer deflection at the moment 

 in the form of a dot. [4.] 



