239 
Following then this plan, Nos. 1 and 4 show the current when the 
magnets are not excited. Nos. 2 and 5 show the current in a field of the 
“first direction,” and Nos. 3 and 6 show it in a field of the ‘second direc- 
tion.’ It may be observed from the photographs that the streams in series 
A, B, D and E are deflected as if they were flexible conductors bearing a 
current, in so far as direction of deflection is concerned, thus indicating 
that the stream is one of charged particles. 
But some characteristics of the photographed stream are hard to ex- 
plain on the theory that the air is ionized and that the stream consists of 
charged particles. The glow discharge and the negative stream in all 
cases show no deflection in a field of 1,500 gausses. Also the stream goes 
in a straight line after leaving the point instead of following a curved path 
to the opposite electrode, and there seems to be no connection or joining 
of the negative and positive streams. In some ways it acts as the air and 
vapor streams investigated by Professor Foley and Mr. Haseman. In 
case of the silent discharge, where the machine was run at its lowest possi- 
ble speed and the potential was the lowest, the stream retains the same size 
as far as it can be traced. In series B there is not much change in the 
width of the stream. Series E shows the stream growing broader as the 
distance increases from the electrode. Series A shows a still greater 
broadening and D an even greater dispersion. The greater pressure in 
the stream no doubt accompanies the greater potential difference, and 
therefore accompanies the greater dispersion of the stream, as was shown 
to be true in case of air and vapor streams by Professor Foley and Mr. 
Haseman. Series E and B show a greater deflection than any other series, 
and since B was the highest potential brush discharge and E the lowest 
potential spark discharge which could be obtained without a transforma- 
tion of the type of discharge, these few photographs indicate that the great- 
est magnetic deflection is produced when the discharge is on the verge of 
changing from one type into the other. Enough photographs were not 
taken to verify this, however. 
It will be observed in Nos. 1 and 4 of the series E that the stream 
does not always pass along a line directly between the points, even when 
the discharge takes place outside a magnetic field. In the observations 
made such cases were in a minority, the discharge as a rule passing di- 
rectly between the points or nearly so. The cause of its deviation in these 
few cases was not learned. 
