120 



EXPLORATION GEOPHYSICS 



tivities are adjustable from 10 gammas or more per scale division, with a 

 scale range of 40 divisions. The sensitivity is usually adjusted to a value 

 of about 30 gammas per scale division. 



Fig. 46. — Hilger and Watts magnetometers. Left, vertical component instrument; 

 right, horizontal component instrument. A, gauss eyepiece; B, light window; C, mirror; 

 D, case; E, clamp lever; F, tripod head; G, leveling screws; H, auxiliary magnet; 

 I, tripod; J, spirit levels. (Courtesy of Hilger and Watts, Ltd.) 



Fig. 47. — Interior view of Askania horizontal component field balance, a, gauss eyepiece; b, 

 light window; c, mirror; d, instrument case; e, clamp lever; /, cork thermal insulation; k and k', 

 magnetic system; I, quartz knife-edge; m, copper damping plates; n, level bubbles; o, door in case 

 with mirror attached for reading thermometers; p, counterbalances; q, objective lens; r, mirror. 



