ELECTRIC DISCHARGE WITH THE CHLORIDE OF SILVER BATTERY. 
the coil 815, and the tell-tale tube which, is placed close to T T', so that it may be 
photographed at the same time as T T. The A terminal of the battery is connected 
to the primary of the coil at P', the other end of the primary being connected through 
the wire P to the tube ; the second wire of the tube is connected to the Z terminal of 
the battery ; the ends of the secondary wire of the coil to the terminals of the tell-tale 
tube. The condenser is not shown in fig. 68. 
Fig. 68. 
In all the figures on Plate 18 relating to these phenomena, namely, figs. 6, a and b, 
7, a and b, and fig. 8, a and b, the copy of the a photograph represents the condition of 
things when the condenser is not connected with the battery, the copy of the b photograph 
the phenomena when it is connected. In the a series there is no stratification in the 
vacuum tube and no illumination of the tell-tale tube, in the b series there is stratifi- 
cation, and the tell-tale tube is illuminated in consequence of an induced current, 
produced by the periodic overflow of the condenser and consequent pulsation of 
current, which coincides with the production of strata. 
Tube 42, Coal Gas. 
231. — Tube 42 is represented in fig. 37, its extreme length is 12'5 inches, between 
the terminals 2T25 inches, its greatest diameter 3 inches, the resistance 
85,000 ohms. 1080 cells, C. 0'00912 W, without the condenser, produced 
a nebulous light around the cup-shaped negative and reaching the heart- 
shaped positive, but without any strata being visible in the discharge ; 
the tell-tale tube was not illuminated, thus showing that there was no 
detectable pulsation in the current, fig. 6, a, Plate 18. When, however, the 
condenser was connected with the battery by pressing down the key K, fig. 66, 
then the discharge was a stratified one, and the tell-tale tube indicated by its 
illumination that the current through tube 42 was a pulsating one, fig. 6, b, 
Plate 18. These two figures are copied from photographs each taken in 60 
seconds. 
2 G 
MDCCCLXXV III. 
