334 



MAGNETIC METHOD 



[Chap. 8 



Mi'rror 



She) Bar_ 

 Copper- 

 Damptr 



2. The Schmidt horizontal balance^ is intended for the measurement of 

 horizontal intensity anomalies. It is so designed that it fits the vertical 

 magnetometer tripod. Therefore, vertical intensity measurements may 

 be followed immediately with horizontal intensity determinations at the 

 same station. The first horizontal magnetometers were constructed with 



a cylindrical case surrounding a 

 vertical magnetic system bal- 

 anced on a knife edge (see Fig. 

 8-23). For the later models no 

 special case was made, the round 

 case shown in Fig. 8-18a being 

 adapted to both horizontal and 

 vertical magnetometer systems. 

 This is a simplification from 

 the construction point of view, 

 it is not feasible to use one case 

 and to insert first the vertical 

 and then the horizontal mag- 

 netic system. 



The construction of the hori- 

 zontal and the vertical balances 

 is similar. In the earlier type 

 of system illustrated in Fig. 

 8-19 an aluminum cube carries 

 a knife edge and two magnetized 

 steel blades, mounted in a verti- 

 cal position so that when the 

 system swings in the magnetic 

 meridian, a deflection will be 

 produced by the horizontal 

 intensity anomaly. The nor- 

 mal horizontal intensity is 

 balanced by unsymmetrical 

 mass distribution ; the center of 

 gravity is to the north and 

 above the axis of rotation. 

 The magnetic system carries a 

 mirror whose deflections can be read on an autocollimational telescope 

 system as in the vertical magnetometer. Thermometers, levels, dampers, 

 and arresting mechanism are likewise provided. In the more recent types, 

 compensated systems and telescopes with teleobjective lenses are em- 



Knob 



Fig. 8-23. Section of Askania-Schmidt hori- 

 zontal magnetometer. 



"Heiland, op. cii., 261-313 (1929). 

 2« lUd. 



