ELECTRIC DISCHARGE WITH THE CHLORIDE OF SILVER BATTERY. 
75 
On making the straight wire positive the phase was produced which is represented 
in Plate 9, fig. 2 ; this is copied from a photograph obtained in 7 seconds. It will 
be noticed that several of the cup-shaped strata after the first three, counting from the 
negative terminal, are followed by a secondary series which are t-ongue-shapecl; these 
latter kept continually disappearing and reappearing precisely in the same position, 
so that the photograph is in no way indistinct or blurred. 
On introducing a resistance of 230,000 ohms, the particular phase to which it is 
desired to call attention was obtained ; it is represented in Plate 9, fig. 3, copied 
from a photograph obtained in 7 seconds. The somewhat confused discharge near 
the positive shown in the previous figure has disappeared, and tongue-shaped strata 
cross each other like the component lines of the letter X : fig. 3 is an exact copy 
of the perfectly distinct photograph. Such complex phenomena present many 
difficulties in the way of a theoretical explanation of the forces which concur in their 
production. 
Potential necessary to 'produce a discharge between discs at a constant distance 
and at various pressures. 
In the first instance, at the suggestion of Professor Mascart, an experiment was 
made in order to ascertain whether there was either any condensation or dilatation 
of the gas about the terminals before the actual passage of the discharge. In order 
to do this an apparatus was constructed as shown in fig. 74. 
It consists of a glass cylinder, 4'35 inches inside diameter, the depth of which is 
accurately the same in every part, 1‘6 inch, so as to ensure the parallelism of two 
glass discs which close its ends. Its cubical content, exclusive of the terminals, was 
found to be 385 cub. centims. 
These are held in contact with the ends of the cylinder by means of screw-clamps 
made of ebonite, and the whole apparatus is supported on a tripod ebonite stand, which 
is fastened to a square wooden foot. Attached parallel to the top and bottom glass 
discs, by means of flanged-screw rods, are two brass discs with rounded edges 3T inches 
diameter; these are maintained at a distance of 0T3 inch, at which the discharge of 
11,000 cells would only just take place. 
The ends which project through the glass discs are furnished with binding-screws for 
attaching wires from the battery. 
On the side of the cylinder is a tubulure in which is fitted a gauge containing strong 
sulphuric acid, so as to dry the inside of the apparatus, and to indicate whether any 
condensation or dilatation of the ga,s contained in the cylinder occurs on connecting 
the metallic discs with the battery by means of the contact-key. The edges of the 
cylinder were rubbed with grease, and care was taken to prove that the apparatus 
was perfectly tight, by causing the fluid in the limb of the gauge to stand for some 
time higher than that in the bulb. When contact was made with a battery of 9800 
l 2 
