MAGNETIC METHODS 



119 



The following theory and description apply generally to all Schmidt- 

 type field magnetometers, whether the Askania, made in Germany, the 

 Ruska magnetometer made in Houston, Texas, or the Hilger and Watts 

 magnetometer, made in England. 



Two types of Askania- Schmidt field balance are available ; one measures 

 the vertical component of the earth's field and the other the horizontal 

 component. In both instruments the mass distribution of the balance system 

 is so arranged that the force exerted by gravity holds the magnetic system 

 in such a position that it is acted upon chiefly by the desired component 

 (vertical or horizontal) which is to be measured.f 



Fig. 45. — Views of the Ruska magnetometers: vertical component instrument, left; horizontal 

 component instrument, center; and the Scout magnetometer, right. A, gauss eyepiece; b, window; 

 C, mirror; D, case; E, clamp lever; F, tripod head; G, leveling screws. (Courtesy of the Ruska 

 Instrument Corporation.) 



Exterior views of late models of the Askania-Schmidt type magneto- 

 meters are shown in Figure 48. 



Views of the Ruska magnetometers are shown in Figure 45. The 

 standard vertical and horizontal component instruments can be adjusted 

 for sensitivities of 10 gammas or more per scale division, with a total 

 scale range of 120 divisions. The Scout vertical component magnetometer 

 has a sensitivity of 25 gammas per division, and a scale range of 3000 

 gammas. This instrument is small and light-weight, and is designed 

 primarily for reconnaissance and mining surveys. 



The Hilger and Watts instruments are shown in Figure 46. The sensi- 



t J. Wallace Joyce, Manual on Geophysical Prospecting with the Magnetometer, U. S. Bureau 

 of Mines Publication (printed by the American Askania Corporation, Houston, Texas, 1937). 



