HALL. — DEVIATIONS OF FALLING BODIES. 349 



placed perhaps 10 era. of the wire, not far above the ball as the whole 

 hung suspended in place, in a horizontal magnetic field which probably- 

 averaged, for the 10 cm. mentioned, a strength more than three thousand 

 times that of the earth's horizontal magnetic field. I then made obser- 

 vations on the position of the wire with Jield off, field on {direction 

 north), field on (direction south), repeating the changes a number of 

 times. I found no effect of which I could be sure, although the condi- 

 tions were such as to make the magnetic deflecting action on the wire 

 perhaps twenty or thirty times as great as the corresponding action which 

 could have been exerted by the earth's magnetic field during the ordinary 

 course of the experiments. 



An attempt to measure approximately the magnetic deflection of an 

 iron wire, substituted for the copper wire in the artificial magnetic field, 

 failed, for the reason that a bit of thread, used to piece out the suspension 

 at the top of the iron wire, by its continual untwisting kept the plumb- 

 ball in a state of slow rotation, which produced a deflection unless the ball 

 happened to be placed in a perfectly symmetrical position in the vessel 

 containing the water surrounding it. The rotating ball acted as if slightly 

 repelled by the nearer side of the vessel. 



