406 



Mr. G. Chrvstal on Bi- and Unilateral 



V and P' have now disappeared, and the equilibrium at has 

 become stable. This corresponds to case (1) of the second 

 state of the phenomenon. 



Lastly, suppose B small and a not zero, then Ave must dis- 

 ]-)lace the origin in curve (1) to the right, say. We thus get 

 fig. 3. Here / = a ; so that 0' represents the position of 



Fig. 3. 



equilibrium when there are no currents. P and P' are un- 

 stable ; and Q represents a single stable position when the cur- 

 rents are going. The deflection corresponding to this posi- 

 tion is 7i, where n is the foot of the ordinate of Q, and n is 

 > 0', in accordance with the experimental facts above stated. 



Similar reasoning would show that if the magnet had been 

 deflected in the opposite direction, the alternating currents 

 would have increased the deflection in the same direction. In 

 fact the above simple graphical representation embraces the 

 experimental facts, as I have observed them, completely. 



It may render the above clearer to give the results of one 

 of the earlier experiments with a Thomson's galvanometer. 

 No care was taken to adjust the scale parallel to the windings 

 of the coil ; so that the results are not symmetrical ; but they 

 illustrate perfectly the nature of the phenomenon in its second 

 state. 



Position of spot 

 with no current. 



Position of spot 

 with currents going. 



Difference. 



+ 173 

 + 50 



- 2 



- 14 



- 20 



- 64 

 -193 



+ 350 

 + 108 

 + 10 



- 15 



- 30 

 -134 

 -355 



177 

 58 

 12 



10 



70 



162 



In this case the mirror was very nearly parallel to the coils 

 when the spot of light was at —14 on the scale. It will be 

 seen from the above that the effects are of a very decided and 

 unmistakable character. I may also add that I have got 

 similar results with three different galvanometers. 



