124 Intelligence and Miscellaneous Articles. 



from the point where the kathode wire pierces the wall of the 

 tube. All attempts to accelerate or retard the motion by means 

 of strong bar magnets, as in Barlow's wheel, were without effect. 

 Placing the tube at various distances from the induction-coil and 

 giving the disk all possible positions in the earth's field produced 

 no change in the rotation. A more decided rotation was produced 

 by using the brush-discharge of a 24-inch Holtz machine. Xo 

 rotation has been produced as yet when the leading wires were 

 in metallic contact with the conductors of the Holtz machine, 

 but when the leads consisted of rods having spherical terminals, 

 separated by short spark intervals, the rotation was always seen. 

 When the loose disk w r as made the anode, no tendency to rotation 

 Avas observed. Thus far all attempts to produce the effect in air 

 of ordinary pressure have failed, but the work in this direction is 

 not yet concluded. 



In the tube used, the tendency to rotation was not observed 

 until by long use the vacuum had become very high, and it has now 

 nearly reached the limit where the sparks pass around the tube, 

 rather than through it. 



The leading-in wires are at right angles to each other in the tube 

 used. Tubes are now in preparation which will have rotary disks 

 facing each other as well as at right angles to each other, and 

 various other features, by which it is hoped that many questions 

 which at once suggest themselves may be answered. There is 

 much reason to suspect that the gas particles do not shoot off 

 normally from the surface of the disk, but in a vortex the axis of 

 which is in the two dark spots opposite the kathode faces. The 

 fact that the anode does not respond, and that similar experiments 

 in open air have thus far failed, seems to point to the kathode dis- 

 charge as the direct active agent. This view is not easily reconciled 

 with the result of the experiment made by Crookes with the heini- 

 cylindrical kathode (« Nature/ July 3, 1879, p. 229, fig. 3), but the 

 figure shown does not seem to quite agree with the description of 

 it. Experiments are now in preparation which will decide this 

 question. It is possible that the rotation observed is a direct 

 action and reaction between the current in the disk and the ex- 

 ternal field due to the current. In this case the rotation apparently 

 ought to be producible in open air, and on the anode terminal of 

 the Crookes tube. 



Whatever may be the direct agency producing this rotation, it 

 seems apparent that we now have an experimental basis for impos- 

 ing a term representing a rotation into the equations representing 

 the conditions within a conductor. — Transactions of the Academy 

 of Science of St. Louis, vol. vii. no. 7 (May 8, 1896). 



