358 



MAGNETIC METHOD 



[Chap. 8 



the case. For determination of inclination, a dip circle with two long 

 needles is used in the older instruments, while in the more recent models 

 an earth inductor attachment is employed. In this country the U. S. 

 Coast and Geodetic Survey and the Carnegie Institute magnetometers are 

 predominantly used. In England the Kew pattern and the Indian pattern 

 magnetometers are applied. In Germany instruments have been de- 

 signed by Schmidt and Nippoldt and have been constructed by the Askania 

 Company. Details of the magnetometer used in this country may be 



Fig. 8-36. Earth inductor rings. 



found in publications by D. Hazard*^ and J. A. Fleming.^^ An illustra- 

 tion of the Askania magnetic theodolite is given in Fig. 8-35. 



2. Earth inductors. Because of the errors and complexities of dip-circle 

 measurements, the inductor inclinator, or earth inductor, has come into 

 increased use on magnetic theodolites and in observatories for the deter- 

 mination of inclination. The earth inductor is like a small dynamo. 



" D. Hazard, Directions for Magnetic Measurements, 3rd ed. U. S. Coast & Geod. 

 Surv. Ser. No. 166 (Washington, 1930). 

 " Terr. Mag., 18, 105-110 (Sept., 1913). 



