in Nickel and Cobalt. 



165 



this series begins. The question, of course, arises whether 

 there may not have been induced by this means a permanent 

 magnetism sufficient to affect the results of subsequent expe- 

 riments. In order to settle this question as far as possible, a 

 small piece of nickel film, of the same quality as the strip in 

 use, was first subjected to the action of a field of about 7000 

 or 8000. It was then placed in a field of perhaps 1500 or 

 1600, whose direction was such as to tend to reverse any per- 

 manent magnetization which might have been induced in the 

 film by the previous field. It was found that now in the 

 second field the nickel became magnetized, temporarily at 

 least, in the direction of that field. No attempt, I believe, 

 was made in any case to detect the permanent magnetization. 

 In this trial the small piece of nickel film was magnetized, 

 not in the direction of its thickness, but in a lateral or longi- 

 tudinal direction; so that we do not here have an exact parallel 

 to the case of the strip ; but it seems probable that magneti- 

 zation in the direction of the shortest dimension would be 

 much more easily disturbed than that in a longitudinal direc- 

 tion. Moreover, just before the series of experiments was 

 begun whose results are here published, quite a long series 

 was made with magnetizing forces about equal to those with 

 which the published series begins ; and this treatment would 

 have tended, no doubt, to obliterate any traces of permanent 

 magnetism due to the action of previous higher orces, even if 

 this permanent magnetism had been much greater than we 

 have any reason to suppose it was. On the whole,, therefore, 

 the probability of any considerable error from this source 

 seems to be very small, 



Date, 



Temperature. 



Tan a. 



gorSB. 



?.'xl0 10 . 



Feb. 24,1881 







18-5 



•330 



1667 



209-3 



25, „ 



22*0 



•332 



1655 



211-1 



26, „ 



21-5 



•336 



1664 



208-1 



26, „ 



160 



•336 



1735 



213-2 



28, „ 



19-5 



•333 



2512 



314-3 



28, „ 



20-0 



•333 



2512 



307-0 



Mar. 1, „ 



200 



•330 



4734 



596-1 



2, „ 



19-5 



•327 



4775 



596-4 



5, „ 



19-0 



•338 



6540 



735-5 



7, „ 



200 



•339 



6415 



726-7 



7, „ 



20-5 



•340 



7996 



761-0 



10, „ 



21-5 



•324 



7791 



771-0 



11, „ 



21-0 



•312^ 



9 



8712 



783-5 



11, „ 



18-5 



•313 





8644 



755*1 



12, „ 



20-0 



•338 



w . ' 



9561 



772-4 



12, „ 



18-0 



•338 



§'2 



970S 



759*8 



14, „ 



21-0 



•326 



p g 



10720 



793-3 



14, „ 



21-0 



•323; 



^ 



10290 



785*6 



