. Mining and Scientific Press . THAI I \ Tim la; MAGNETOMETER, PROVIDED Willi TANGNDSIN1 - LRMSj FOH RI IDING HORIZONTAL !\l i N8ITD3S. THOMSON-THALEM MAGNETOMETER, FOR READING VERTICAL INTI \ -I I II 9 The storing or carrying of magnetometric instruments in proximity to direct-current generators or motorsshould be avoii led. For instance-, while riding on an elec-tric street-car the magnetic needles may become de-mag-netized, or the poles may become reversed, thus renderingthe magn r worthless for field use until re-mag- netized and adjusted. The greater the sensitiveness of 440 MINING AND SC
. Mining and Scientific Press . THAI I \ Tim la; MAGNETOMETER, PROVIDED Willi TANGNDSIN1 - LRMSj FOH RI IDING HORIZONTAL !\l i N8ITD3S. THOMSON-THALEM MAGNETOMETER, FOR READING VERTICAL INTI \ -I I II 9 The storing or carrying of magnetometric instruments in proximity to direct-current generators or motorsshould be avoii led. For instance-, while riding on an elec-tric street-car the magnetic needles may become de-mag-netized, or the poles may become reversed, thus renderingthe magn r worthless for field use until re-mag- netized and adjusted. The greater the sensitiveness of 440 MINING AND SCIENTIFIC PRESS September 24, 1921 the magnetometer, the more reliable the results. The ver must, therefore, be prepared to re-magniand adjust his magnetometers in the Hold in order toensui acy. I i sions Prom Magnetic Surveys. Every attraction upon the magnetic needle extending o\er aarea does ool indicate necessarily the pn sence of amineral deposil of commercial value. Volcanic rocks andlava, more or less impregnated with magnetite, occur atnumerous places, but thej never contain magnetite insufficient quantity to be classed as
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