ELECTRIC DISCHARGE WITH THE CHLORIDE OF SILVER BATTERY. 
231 
The gases in all probability receive impulses in two directions at right angles 
to each other, that from the negative being the more continuous of the two/'' 
Metal is frequently carried from the terminals and is deposited on the 
inside of the tube, so as to leave a permanent record of the spaces between the 
strata. 
2. As the exhaustion proceeds the potential necessary to cause a current to pass 
diminishes up to a certain point, whence it again increases, and the strata 
thicken and diminish in number, until a point is reached at which, notwith- 
standing the high electromotive force available, no discharge through the 
residual gas can be detected A Thus, when one pole of a battery of 8040 cells, 
was led to one of the terminals of tube 143, fig. 37, which has a radiometer 
attached to it, the other terminal of the tube, distant only 0*1 inch, being 
connected through a sensitive Thomson galvanometer to the other pole of 
the battery (earth), the current observed was not greater than that which 
was found to be due to conduction over and through the glass. Although no 
current passed, the leading wires acting inductively stopped the motion of 
the radiometer, as has been observed by Mr. Justice Grove. 
3. All strata have their origin at the positive pole. Thus, in a given tube, with 
a certain gas, there is produced at a certain pressure, in the first instance, 
only one luminosity which forms on the positive terminal, then, as the 
exhaustion is gradually carried further it detaches itself, moving towards 
the negative, and being followed by other luminosities, which gradually 
increase in number up to a certain point. 
4. With the same potential the phenomena vary irregularly with the amount of current. 
Sometimes, as the current is increased, the number of strata in certain 
tubes increases, and as it is diminished their number decreases ; but with 
other tubes the number of strata frequently increases with a diminution of 
current. If the source of the current is a charged condenser, the flow being 
from one of its plates through resistances and the tube to the other : then, 
as the potential of the condenser falls and the current diminishes, the number 
of strata alters ; if the strata diminish in number with the fall of potential, 
then the stratum nearest the positive wire disappears on it, the next then 
follows and disappears, and so on with others ; if, on the other hand, the 
charge of the condenser is very gradually increased, the strata pour in, one 
after the other, in the most steady and beautiful manner from the positive. 
5. A change of current frequently produces an entire change in the colour of the 
strata. For example, in a hydrogen tube from a cobalt blue to a pink. 
* De La Rue and Muller, Phil. Trans., 1878, Vol. 169, p. 90 and p. 118. 
t From observations with pressure varying from 6'4 to 146'1 millims., Wiedemann and Ruhlmann 
conclude that the accumulation requisite to produce discharge increases with the pressure at first 
quickly, then more slowly ; towards the upper limit of their experiments it becomes nearly proportional 
to the pressures. 
