﻿Oscillations on Iron in a Magnetic Field. 



Ill 



solenoids each of 3270 turns of No. 20 copper wire wound in 

 6 layers on a length 59 cm. of split brass tube. They were 

 placed horizontally on one and the same magnetic east- west 

 line, but on either side of a mirror magnetometer. The mag- 

 netometer-needle was in the common axis of the two solenoids. 

 The solenoids were connected in series, and so adjusted in 

 position that when a large current was passed through them the 

 magnetometer-needle was undisturbed. A liquid resistance, 

 a Weston milliammeter, suitable switches and commutators, 

 and a battery of six secondary cells, completed the solenoid 

 circuit. The coil destined to be the seat of the oscillations 

 consisted of 1252 turns of No. 2b* copper wire wound in a 

 single layer on 70 cm. of a glass tube 05 cm. in external 

 diameter, and had a resistance of about 3 ohms. The whole 

 coil was wrapped in paraffined paper and pushed into the 

 brass tube of the east solenoid. 



Fig. 1, 



.^~ - 5 H 



The iron wire examined was unannealled Swedish charcoal 

 iron, diameter 0*749 mm., and was used always in lengths of 

 56 cm. Its characteristic curve is given in tig. 1. The mag- 

 netometer was a silk-suspended mirror carrying four very 



