417 
iron arising from its rotation. 
former forces are greater than the latter, there being only 
one instance of the contrary, and that in a position where the 
effects are so small, that a trifling error of observation would 
account for the difference. Taking a mean of all the obser- 
vations, these forces appear to be in the ratio of 19 to 13, or 
very nearly 3 to 2. It is evident then that the polarising of 
the iron in the same direction will account for the phseno- 
mena in both cases, but that the intensity of the polarity 
during the rapid rotation is greater than of that which 
appears to be permanent after the rotation, whether slow or 
rapid, has ceased ; and that the phenomena observed during 
rapid rotation are such as we should expect from those which 
I have so fully described as arising from rotation, without 
regard to its velocity. 
