180 



C. G. KNOTT 



In Table II., the first column gives the different cyclic twists, the 

 second column the total ranges of intensity, and the third column 

 numbers proportional to the areas of the closed cycbc curves. These 

 areas are easily calculated from the differences given in the fourth 

 column of Table I, and are in fact the best indicators of the nature 

 and magnitude of the magnetic lagging or priming. 



Table II. 



Curve B shows how the range depends on the twist. The in- 

 crease is rapid and nearly steady for the small twists ; but for higher 

 twists than ± 2 7T, the rate of increase of range becomes very small. 

 It should ba mentioned that this point was very fully investigated 

 by Mr. Imagawa ; and that the conclusion just stated does not rest 

 merely on these five particular cases. 



Curve C shows the march of the area of the cyclic curve with the 

 twist. Thus the area begins positive at the low twists, indicating 

 true magnetic lagging. For a twist a little greater than ± tt, the 

 area changes sign, so that we have magnetic priming. For higher 

 twists the area goes on increasing at a very rapid rate. So far as the 

 experiments were carried there seems to be no limit to the increase of 



