228 



Intelligence and Miscellaneous Articles. 



The dotted curve on the accompanying figure represents the 

 relation between — and H calculated by the formula (1), and the 

 plain curve the results of observations. 



pi 



The mean difference between the values of -=• observed and cal- 

 culated is equal to about 6*7 X 10 -9 or to 3 per cent, of the maximum 

 value. This difference is too great for an exact formula, but as a 

 first approximation the formula (1) may be accepted. Thus I may 

 set forth the results of my investigation in the following form : — 



A soft iron wire, 39*5 cm. long and 0083 cm. thick, with a longi- 



c/r. 

 tudinal stress of 380 — — 5 and placed in a maqnetizinq solenoid 86 cm. 



J mm. x j j 



long and 3*85 cm. 2 in mean section, by cyclic magnetization shows a 

 change of length, which may be expressed, as a first approximation, 

 by the formula 



10 9 x j = 0-000044834 x F - 0-00365023 x IH + 0-0301531 x H 2 , 



SI 

 where -j is elongation per unit of length, I magnetization, and H 



magnetic force. — Abstract of a paper published in the Journal of 

 the Russian Physico-Chemical Society, xxvi. pp. 253-264. 



Physical Laboratory, 

 University of St. Petersburg, Russia. 



