80 Trans. Acad. Sci. of St. Louis. 



machine. It is necessary that the knobs be placed above 

 the ends of the tube. The protruding ends of the wire 

 are slightly lifted just before the sparks occur. This 

 prevents bending of the wire around the edge of the 

 glass at the end of the tube, from interfering with the 

 longitudinal creeping of the wire. 



The discharge gaps at the ends of the glass tube were 

 made equal. The discharge knobs had equal diameter. 

 The gaps usually had a length of four or five cm. each, 

 so that discharges could be freely produced, at intervals 

 varying from half a second to three seconds. 



The machine was in a glass case containing a supply 

 of calcium chloride, and warmed inside by a one-kilowatt 

 heater. The wire was obsei^'^ed by means of a telescope 

 magnifying about 27 diameters. No longitudinal motion 

 of the wire due to a single spark, can be detected by ob- 

 servation with this telescope, but the summation effects 

 of three or four sparks is plainly to be seen. The wire 

 gradually creeps along within the tube in the opposite 

 direction from that in which the negative discharge 

 passes through it. In one case the wire was placed 

 symmetrically in the tube so that each end projected 1.2 

 cm. The sparks were passed into the side of the wire 

 at the end of the glass tube. A condenser of sheet glass 

 having on each side a metal plate of about 1,000 sq. cm. 

 was used. Sparks were passed into the wire for about 

 three hours, during which time the displacement of the 

 wire was 1.2 cm. due to about 3,500 discharges. As the 

 wire was gradually displaced from the position of sym- 

 metry, sparks at the positive end occasionally entered 

 the wire at its end. At the close of the operation when 

 the end of the wire was at the end of the tube, all of the 

 sparks at this end, entered the wire at its end. It may 

 be that an end effect due to interaction between the wire 

 and the air is thus increased. At each end of the wire 

 there is a point discharge, but these opposing effects on 

 the wire seem to be greatest when no spark is passing, 

 and to cease when the spark has passed. 



