Prof. G. Wiedemann's Magnetic Researches. 67 



of a Mascart's electrometer, the needle of which was charged 

 from a battery of 100 copper-water-zinc elements. Its de- 

 flection was read by means of a telescope and scale distant 

 1 metre from the mirror attached to the needle. 



In the following Tables E denotes the deflection of the 

 needle of the electrometer, M the temporary moment of the 

 magnet, I the intensity of the current measured by lowering 

 the ring. 



In the first series of experiments the iron bar was repeatedly 

 magnetized by currents which in each case rose to a definite 

 maximum intensity determined by the electrometer, and were 

 then reduced to zero. The permanent moment was deter- 

 mined in each case after complete cessation of the current 

 (E = 0). The results obtained were as follows : — 



(1)E 5 13 13 17 23 17 12-8 9-5 6 



M 55-5 — 61 157 379 323 278 231 177 99 



(2)E 5-5 9 13-2 18 23-5 17-7 12-7 9 5-8 



M 146 184-6 230-2 291-3 381 323 269 228 184 109-5 



(3)E 5-8 9 13 18 23-2 16-7 13 9 5-8 



M 155 190-6 234-5 301-2 381 309 270-5 228-2 185 113 



(4)E 5-8 8-9 13 18 25 17-5 13 9 5-8 



M 159-2 190 236 296 394-2 322-2 272 229-8 187*5 116-2 



and after ten similar magnetizations, 



(15) E 5-8 9 13 17 23 16-5 13 9 58 



M 173 206 249-3 303 380-5 319 281-5 237'6 194-2 126-2 



In another series of experiments a fresh iron bar was re- 

 peatedly magnetized to the same temporary maximum moment 

 M # ; then the intensity of the current was decreased to zero, 

 and the permanent moment M read off after complete cessa- 

 tion of the current. 

 Thus :— 



1. 2. 3. 4. 5. 10. 



M; 320 320 320 320 320 320 



m 90 94 96 97 975 98'5 



and the temporary moment M after the eleventh magneti- 

 zation : — 



I 14 20-7 27 34 . 42-5 52-2 62 71 



M 137 157-5 176 200 226 258 294 317 



I 60-8 45-5 36-7 27 21-3 15-8 14 



M 292-2 254-5 225-6 199 176 1552 150 



It follows from these observations that even after an iron 

 bar, by repeated temporary magnetization, either to the same 

 maximum of temporary magnetism, or by currents which 

 always attain the same maximum of intensity, has attained a 

 permanent condition, the temporary moment corresponding 



F2 



