ELECTRIC DISCHARGE WITH THE CHLORIDE OP SILVER BATTERY. 157 
some threading themselves on it, as shown on the left of fig. 33 ; but after a lew 
seconds the strata widened out as on the right-hand figure, then other changes 
occurred, and the first phases have never been reproduced. 
Fig. 33. 
TUBE 123. 
Another case is presented by the nitrogen tube fig. 34, the right-hand figure 
showing the first phase, and the left-hand figure a second phase, which in its turn 
has for ever disappeared, and has been replaced by the ordinary disc-form of 
strata. 
Fig. 34. 
After spending much time in experiments with tubes prepared for us by Dr. 
Geissler, Messrs. Alvergniat Freres, of Paris, and Mr. Hicks, of Hatton Garden, 
with the vexation of finding that we could not often enough repeat our experiments, 
we ultimately came to the conclusion to have others made, but not exhausted, and to 
perform ourselves the charging and exhaustion.* The tubes we usually employ have a 
glass stop-cock fitted to them at each end ; they are 32 inches long, and from 1 *75 to 
2 inches in diameter ; the terminals are of aluminium, and about 29 inches apart, one 
being a ring, the other a wire bent at a light angle, so as to point in the direction of 
the axis of the tube (see No. 144, fig. 37), for we have found that the phenomena vary 
according as the ring or wire is made positive. These we exhaust and fill with 
any gas we may wish to experiment with, and gradually exhaust again, noting the 
phenomena presented at different pressures, different potentials, and with different 
amounts of current. We re-fill and exhaust the tube again and again, and mostly 
obtain, under the same conditions, as nearly as possible the same phenomena, of which 
we are careful to make sketches and, if possible, to obtain photographic records. 
In some cases we make use of tubes provided with a calibrated chamber between 
two stop-cocks, as a — b, No. 145, fig. 37, the chamber in this particular case having 
2 “Woth of the capacity of the tube. After a tube has been exhausted so as to 
* Gassiot was driven to the same conclusion ; he says, in speaking of Geissler’s tubes : “ I reluctantly 
laid them aside, and for all experiments I have to describe each tube was charged and exhausted by 
myself or in my presence.” 
