240 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



The following observations were taken for the 26th and 28th reversals 

 one 3-step reversal coming between the two. No measurements are 

 here recorded for the odd-numbered reversals, which were, of course, 

 in the opposite direction to the even-numbered ones. 



The 29th to the 82d were 1-step reversals. Of these the 30th, 32d, 

 80th and 82d are recorded. 



Rev. 



30th 

 32d 



80th 

 82d 



Amp. Read. 



8.90 

 8.90 



8.90 

 8.90 



Ball. Galv. 



10.55 

 10.54 



10.51 

 10.51 



Average Throw. 



10.55 

 10.51 



The difference between the average of the twenty-seven even-num- 

 bered reversals, 30th-82d, and the average of the first two recorded 

 1-step reversals, 10.55, is 0.1 per cent. The flux change per reversal 

 has decreased slightly, from 10.55 to 10.51, during the course of the 

 3-step reversals. That this is characteristic of the specimen during 

 its early magnetic history will appear from the data following. 



In this case the maximum value of H is 3.46, of B 1394. Thirty 

 3-step reversals were taken and then the 31st and 33d observed. 



