652 



Messrs. K. Honda and S. Shimizu on the 



the lower brass wire. The upper wire was clamped to a 

 small tripod which rested on the top of a magnetizing coil 

 provided with hole- slot- and plane arrangement. One end 

 o£ the accumulator was connected with the tripod while the 

 other was led to the mercury pool placed under the suspended 

 wire. The wire hung vertically in the axial line o£ the coil, 

 which was 30 cms. long, and gave a field of 37*97 c.G.s. units 

 at the centre by passing a current of one ampere. The ver- 

 tical component of the terrestrial magnetic field was com- 

 pensated by placing another coil in the interior of the 

 magnetizing coil. The twist was measured by scale and 

 telescope, by which a torsion of 0'2" per cm. was easily read. 



The preliminary experiment showed that the resistance to 

 the twist offered by the mercury in the pool was not negli- 

 gibly small when the thick brass wire was dipped into the 

 mercury. The resistance was especially noticeable when the 

 brass wire carried a narrow rectangular piece for the purpose 

 of damping. Hence, in order to efface the resistance, a non- 

 magnetic nickel-steel wire 05 mm. thick and 5 cms. long was 

 soldered to the lower end of the brass wire and dipped into 

 the mercury pool. By this the damping of* the torsional 



