440 Sir W. Thomson on [May 23, 



found to differ for the two temperatures, and for different weights : 

 thus approximately : — 



Amount of 

 weight " on" 

 and off." 



Magnetizing force for which the " on " and 

 " off " produce no change of magnetism. 



At atmospheric tem- 

 perature (being 

 about 15° C.) 



At temperature 

 100° C. 



7 lbs. 



266 



2i0 or 290 



14 „ 



281 



286 



21 „ 



288 



310 



The maximum effect of the "on " arid " off " was found in each 

 case with magnetizing force of from 50 to 60 of the arbitrary scale 

 diyisions (or about four times the Glasgow vertical force). Its 

 amount differed notably, though not greatly, with the temperature, 

 and, as was to be expected, greatly with the different amounts of 

 pull ; but it was not nearly three times as much with 21 lbs. as with 

 7 lbs. ; thus approximately : — 



Amount of 

 weight " on " 

 and " off." 



Maximum effect in the way of augmentation 

 of magnetism by " on " and diminution 

 by " off." 



Temperature about 

 15° C. 



Temperature 100° C. 



7 lbs. 



14 „ 

 21 „ 



J" 31 scale divisions "1 

 < of ballistic gal- V 

 (_ vanometer. J 



35 do. do. 



54 do. do. 



25 scale divisions. 



32-4 do. do. 

 50-3 do. do. 



The curves all tend to asymptotes parallel to the line of abscissas on 

 its negative side for infinite magnetizing forces ; and they indicate the 

 following ultimate values for the two temperatures, and the different 

 amounts of pull : — 



Amount of 

 weight " on " 

 and " off." 



Effect in the way of diminution of magnetism 

 by " on " and augmentation by " off " when 

 the magnetizing force is very great - 



Temperature 15° C. 



Temperature 100° C. 



7 lbs. 



14 „ 

 21 „ 



f 6 scale divisions of 1 

 < ballistic galva- V 

 [ nometer. J 



13-5 do. do. 



21 do. do. 



3 scale divisions. 



9-2 do. do. 

 15*2 do. do. 



