298 YOSHIJIRO KATO; 



that the wires were subjected to moderate loads. My apparatus was 

 essentially the same as that used by him, but for the sake of clearness 

 I may represent its arrangement. 



w s 



R 



Here, W, the specimen to be tested, is an ordinary soft iron wire, 

 54.86 cm. long and 2.39 mm. thick, so that its sectional area is 4.49 

 sq. mm. To its ends brass pieces of special form are soldered, which 

 allow the wire to be hung in a given position and a given load to be 

 applied to it without disturbance. 



S, the magnetising solenoid, is wound on a straight brass tube, 1.2 

 mm. in external diameter, and consists of two sets of coils. The 

 inner coil is put in series with a gravity Daniell cell, B', a resistance 

 box, R', and a circular coil wound on a wooden reel, C. The strength 

 of the current is so adjusted that the magnetic field inside the coil is 

 just equal and opposite to the vertical component of the earth's field, 

 while the direct action of the solenoid itself on the magnetometer is 

 compensated by the coil, C, being placed at a suitable distance. The 

 outer coil consists of 2590 turns of a fine copper wire, and serves for 

 producing the magnetising fields we wish to have. The length of the 

 solenoid is 59.0 cm., and 4~n= 551.6. 



M, the magnetometer is of the ordinary construction, namely 

 four small magnets attached to the back of a small mirror, suspended 

 by a spider's web-line. 1 



1 It was afterwards found that this form of the magnetometer, though convenient, is not 

 very accurate, for the curvature of the mirror changes according to the atmospheric conditions 



