264 
The average speed of all results is used in determining the value of fer: 
m 
4 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- 
2 A € Abe 
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 speed 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 
un-ionized molecules of air continue a short distance at least, in the 
original direction. The unionized air particles would continue along this 
line until seattered by encountering new molecules, while the ions, too much 
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, 
