RESEARCHES ON MAGNETOSTRICTION. 



357 



volume = 6.86 c. c. ; mass — 58 grin.; demagnetizing 

 factor N= 0.020. 



The demagnetizing factor for the rod was calculated on the 

 supposition that N was equal to that of a circular cylinder of the same 

 cross-section. 



The magnetizing coil was 30 cm. long and wound in 12 layers ; 

 its resistance was 0.63 ohm and gave the field of 37.97 c. g. s. units 

 at the middle of the coil due to a current of one ampère. 



The magnetometer consisted of a small bell magnet suspended in 

 a thick copper case by a quartz fibre and provided with a plane mirror. 

 It was placed due magnetic east of the coil and its deflection was read 

 by means of scale and telescope. 



The following table gives the magnetization in different fields : — 



Before we proceed to describe the method employed in the 

 present experiment, it will be worth while to compare the results 



