Nipher—On the Nature of the Electric Discharge. 7 
hydrochinone, which was weak in sodium carbonate. Sim- 
ilar results may be obtained by replacing the torches by 
metal wires, each being armed with about 500 pin-points. 
The black lines on the film are shown even when the plate 
is fixed without being developed. The discharges are not 
discharges through the air or over the surface of the film. 
They are within the body of the film itself, and the film 
shows a distinct depression along the discharge lines. 
These effects may be produced between the terminals 
of the machine, without any ground lines. Similar and 
much larger ball discharges may be made on a surface of 
wood by means of a powerful spark-coil operated by a 
direct current with interrupter. If an alternating cur- 
rent is used in the primary, ball discharges may be ob- 
tained from both terminals simultaneously. They may be 
led into various paths, but cannot be brought together. 
The tracks are burned into the wood, and are two or 
three millimeters in breadth. 
A Crookes tube may be placed in either of these dis- 
charge lines, from the terminals of an influence machine, 
both lines being carried to independent ground contacts. 
If placed in the positive line, the cathode terminal of the 
tube must be turned to the ground. This ground may be 
on a torch, or on a many-pointed conductor, or the 
cathode may be grounded directly on a water pipe. 
Equally good X-ray pictures may be obtained in the posi- 
tive or in the negative lines, with equal times of exposure. 
When placed in the positive line, however, the tube seems 
to operate in a less positive manner than when operating 
in the negative line. When this was first done by the 
author in 1902, the behavior of the tube and discharge line 
created the suspicion that there was a condition in this 
line which was in the nature of a rarefaction. Electric 
, discharges from all surrounding objects, seemed to be 
flowing in upon the tube and the positive line. These ob- 
jects were tipped with brush discharges. The cathode dis- 
charge seemed to be somewhat unsteady and was easily 
