264 ^ 



g 

 The average speed of all results is used in determining the value of 



m 



e 

 given for series D. The values for column 4 are calculated for series 



m 



A, B, C and D only. The values for given in table 4 are determined 



m 

 In the same manner as shown above. 



A great variation exists in the calculated values of the speed, and con- 



sequently in the determination of One cause for this is. no doubt, the 



m 

 error introduced in measuring the potential. Also since the measurement 



of speed is determined by deflection, a large error may be introduced. 



due to convection currents, due to the heated air along the course of the 



spark, and to disturbances of the air due to rapid changes of pressure along 



the spark path. 



It may be observed that the path of the stream from the point (except 

 In case of the spark discharge in the magnetic field), is a straight line and 

 not a curved path. There is very little if any bending to meet the oppo- 

 site point. If we consider the stream as composed entirely of ions we 

 might explain this phenomenon by supposing that the ions either lose 

 their charge immediately after leaving the points, or by assuming that 

 each ion is given a constant acceleration in two directions at right angles 

 to each other. Another view may probably be taken in which the photo- 

 graphed stream is considered to be a mixture of ions and air molecules 

 under different pressure than the surrounding air, hence having a different 

 index of refraction. The ions start at a high six>ed from the point in a 

 direction which depends on the influencing fields. They soon encounter 

 molecules of air imparting their speed to a great extent to the air mole- 

 cules. This bombardment on the air molecules tends to ionize them and 

 to raise their temperature and the original ions, with the ionized and 

 im-ionized molecules of air continue a short distance at least, in the 

 original direction. The unionized air particles would continue along this 

 line until scattered by encountering new molecules, while the ions, too mucii 

 scattered, and with speed too much decreased to produce a well defined 

 air current, travel by some other route to the opposite electrode. 



This view explains the apparent contradiction that, although there 

 must be a carrier of electricity between the points, the photographed 

 stream does not terminate on the opposite point. In case of the rich spark. 



