ELECTRIC DISCHARGE WITH THE CHLORIDE OF SILVER BATTERY. 
105 
76 - 2 centims., between the terminals, a ring, and a straight wire, is also connected to 
the pumps in order to permit of the study of the effect of different bores on the 
phenomena of the discharge when both tubes are at the same pressure. 
The experiments with Tube 199 will necessarily occupy a considerable period, 
partly on account of the long time it takes to exhaust it after each set, partly 
on account of the variety of experiments it is intended to make with it. We now 
propose to describe only a few of the first results we have hitherto obtained. 
Tube 199, Air. 
Pressure 3 m.m., 3947 M, 6300 cells. Two luminosities were formed, as shown in 
Plate 9, fig. 5, the ring negative being surrounded with a nebulosity which 
completely filled the end of the tube. The tube glowed brilliantly with a blue 
fluorescent light, which proved to have great actinic power. The figure is copied 
from a dry-plate photograph obtained in 5 seconds; it records a very curious 
phenomenon, namely, that the outer boundary of the luminosity appears darker 
than the tube. It is to be remarked that while the discharge was reddish (nitrogen), 
the fluorescence of the tube was blue; the effect appears to be due to the absorption 
of a portion of the fluorescent light emanating from the back of the tube in passing 
through the red luminosity. The effect was quite unexpected, and it was thought 
at first that it might have arisen from some peculiarity in the development of the 
dry plate ; it was not therefore until the result had been confirmed by other 
photographs that we ventured on the explanation given. 
Tube 199, Hydrogen. 
Pressure 40 m.m., 56,632 M, 11,000 cells, current 0‘00087 W. A mere speck of 
light both on the positive and negative terminals ; in tube No. 200 there was not 
the slightest glow when the battery was connected with it. The whole of tube 199 
glowed with a blue fluorescent light, notwithstanding that there was only a mere speck 
of illumination on the terminals, and no appearance of light between them. 
Pressure 28 m.m., 36,842 M, 11,000 cells, current 0'00527 W. A spear-head 
shaped luminosity about half an inch long on the positive straight terminal, a 
mere speck of light on the negative ring. No discharge occurred in tuoe 200 at 
the same pressure. 
Pressure 26 m.m., 34,211 M, 11,000 cells, current 0‘00879 W. A fan-shape 
luminosity about one inch long at the positive, a mere speck of light about one-eighth 
of an inch in length on the negative ring. The tube glowed with a blue fluorescent 
light throughout its length. 6300 cells would not pass. 
Pressure 22 m.m., 28,948 M, 11,000 cells, current 0'01412 W. The glow on 
negative extended to three-eighths of an inch, a spear-head luminosity on the positive 
wire, to which it was attached by a very bright wire-like stem not greater in diameter 
than the terminal, A, fig. 87. 
MDCCCLXXX. P 
