INTENSITY OF MAGNETIC AND DIAMAGNETIC FORCES. 755 



nishes in the case of the peroxide of iron more rapidly than with 



iron. 



62. Lastly, that protoxide of nickel, the magnetism of which 



was previously determined, was submitted to experiment in 



exactly the same manner as the peroxide of iron above. The 



heat acquired was about the same, but six Grove's cells were 



used to excite the current. The following are the corrected 



magnetic attractions : — 



grra. 



1. Weighing 0-963 



2. ... 0-963 



3. ... 1-082 



4. ... 1-150 

 .5. ... 1-206 



6. ... 1-325 



7. ... 1-482 



After the fourth weighing the porcelain cup still could not be 

 held in the hand without pain, but this could be done easily 

 after the fifth. After the last weighing but one, the temperature 

 of the cup was below that of the blood. Hitherto the weight 

 required for the separation was determined by placing in the 

 proper scale-pan pieces of paper, the size of which was constantly 

 diminished, and the total weight of which Mas subsequently de- 

 termined. From this time the constant increase of the mag- 

 netism was observed directly for six to eight minutes, because 

 more weights could constantly be added gradually to the last 

 but one. In this way the last weight was found. 



The above results are extremely remarkable, because a con- 

 ■'ihlerable change in the original elevated temperature did not pro- 

 duce any cham/e in the intensity of the magnetism of the protoxide 

 of nickel. The two first weighings agreed perfectly. The sub- 

 sequent ones show at least, that the magnetism at a lower tem- 

 perature increases simultaneously loith the latter in a more acce- 

 lerated degree than at a higher temperature. 



The deportment of the oxide of nickel is probably in close 

 connexion with the observation of M. Pouiilet above mentioned, 

 that nickel ceases to be magnetic at 662° F., which, in accordance 

 with the more recent investigations, signifies merely that the 

 magnetism is reduced to a minimum. 



Is this limit, at which the magnetism vanishes, the same in 

 the case of the protoxide of nickel also? 



