740 PLUCKEB ON THE DETERMINATION OF THE 



filled with the lard-mixture III. (100 lard, 1-6 iron), were made 

 between the different determinations. On first closing the cir- 

 cuit, the watch-glass was attracted by a weight of 69*9 grms. ; 

 this weight continually increased until it attained its maximum, 

 and then again diminished to 70"0 grms. towards the end. The 

 weighings, which followed each other as rapidly as possible, 

 lasted three hours. After each weighing the circuit was opened ; 

 the keepers, however, remained undisturbed. 



With regard to the increase of the force of the electro- magnet 

 at first, and its subsequent diminution, I have preferred not re- 

 ducing the results of the weighings. If merely magnetic sub- 

 stances were concerned, we evidently come nearer to the truth 

 when we consider the attractions as in proportion to the weights 

 requisite for the withdrawal of the normal watch-glass at the 

 various moments. But after numerous obsei'vations, and the 

 investigations contained in the following pai'agraphs, I consider 

 that this proceeding, which in consequence of the great expense 

 of time, augments the inequalities in the intensity of the cur- 

 rent, is unjustifiable in this case, where the electro-magnet acts 

 upon a combination of magnetic and diamagnetic substances. 



Moreover, the corrections have but little influence upon the 

 result. I therefore prefer considering the current as constant 

 throughout. 



40. The second series of experiments was made on the fol- 

 lowing day ; the halves of the keeper had remained undisturbed ; 

 on the addition of fresh acid a similar circuit was set in action. 

 After this had acted for some time, a weight of 70"5 grms. was 

 requisite to withdraw the test watch-glass; and this weight, 

 during the short duration of the weighings, varied 2 decigrms. 

 only. The attraction of the watch-glass, both when empty and 

 when filled with distilled water, was also found to be exactly the 

 same as on the previous day, so that we may resolve the two 

 series into one only. 



In the second series of experiments, the attraction of the watch- 

 glass, when filled with — 



grm. 



1. Alcohol II., amounted to 0*32 



2. Beaten ox-blood 0-32 



3. Mercury 0*05 



4. Sulphuret of carbon 0*31 



5. Hydrochloric acid 0*33 



