6 Trans. Acad. Sci. of St. Louis. 
glass midway between them, so that no disruptive dis- 
charge may occur. The disk is to be in metallic connec- 
tion with the negative terminal. A point of light emerges 
from the pin-point or the pencil mark, and moves slowly 
over the film, curving towards the positive terminal of 
the machine, and leaving a darkened trail behind. Along 
this trail an invisible negative flow is taking place, as can 
be seen by bringing near to it a device which has earned 
the name of ‘‘teazer.’’ This consists of two pins, tied or 
soldered together at their head ends, the points being in 
opposite directions. This is mounted at its middle point 
by means of sealing wax, to a long tube of glass. One of 
these points when presented to the pin-point on the disk 
will usually start the ball discharge, if it fails to appear. 
It was found to be impossible to obtain these ball dis- 
charges from the positive side of the machine. When the 
teazer was used, these discharges would come from the 
point on the teazer and would move towards the posi- 
tive terminal. Plate I of this present paper shows such 
discharges. At the top of the figure were placed two 
disks armed with pins, which were connected to the + 
and — terminals of the machine. Below were two sim- 
ilar disks opposite to those above mentioned, mounted on 
the same photographic plate, which was 10X12 inches in 
size. These disks were in metallic connection with two 
large gas torches hung on insulated supports in the air 
outside of the building. The torches were fed by means 
of long rubber tubes, ending in short metal pipes to which 
the line wires were soldered. Ball discharges came one 
after the other from the negative terminal, some of which 
went to the torch terminal opposite, some turning to- 
wards the positive terminal of the machine. Ball dis- 
charges also appeared from the torch opposite the posi- 
tive terminal and went to that terminal. The plate was 
exposed and developed in daylight, the developer being 
4 Separate plates for the + and — circuits permit them to be more 
widely separated, and give better results. Smaller plates may then be 
ASCE « 
