182 Trans. Acad. Sci. of St. Louis. 



sented in the equations. Until recently the results were 

 wholly negative. While recently experimenting with a Crookes 

 tube 1 observed that the circular aluminum disc of the cathode 

 became slightly loose on the aluminum wire, and that it was 

 constantly rocking in rotary motion on the wire. After sev- 

 eral days of use, during which it had been decided to construct 

 a tube with discs capable of rotation, the cathode disc suddenly 

 became loosened, and began to rotate slowly on the wire as 

 an axis. 



The bearings were somewhat rough, and the disc was not 

 perfectly balanced. It often stopped, but then began to rock 

 against the obstacle until it again freed itself. The direction 

 of rotation was contrary to the hands of a clock, when the 

 disc was viewed from the point where the cathode 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 tul)e at various 

 distances from the induction coil and giving the disc all 

 possible positions in the earth's field, produced no 

 change in the rotation. A more decided rotation was pro- 

 duced by using the brush discharge of a 24-inch Holtz 

 machine. No rotation has been produced as yet when the 

 leading wires were in metallic contact with the conductors of 



CD 



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 disc was 

 made the anode, no tendency to rotation has been 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 discs 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 



