226 
MESSRS. W. DE LA RUE AND H. W. MULLER ON THE 
Tube 44. 
232. — Similar in shape to 42, but with two magnesium spherical terminals 0’375 
inch in diameter, distance between them 2'25 inches, the largest diameter of 
the tube 3'125 inches, resistance 42,000 ohms. With 1080 cells, without the 
condenser, C. 0 '01 331 W, a spherical nebulous glow around the negative ball, 
a slight glow on the positive, and no illumination of the tell-tale tube, fig. 7, a, 
Plate 18. When the condenser was attached the discharge became stra- 
tified, and the tell-tale lighted up, fig. 7, b, Plate 18. These are copied from 
photographs obtained in 60 seconds. 
T'ube 32, Coal Gas. 
233. — This is represented in fig. 37 ; the terminals are of aluminium, the negative 
being a cup 1 inch in diameter, and the positive heart-shaped ; they are 
2’75 inches apart. The elongated bulb is 7 inches long and 4'5 inches in 
diameter, resistance 57,000 ohms. With 1080 cells, C. 0’01390 W, a nebulous 
glow on the negative without any stratification, and a slight glow on the 
positive, but no illumination of the tell-tale, fig. 8, a, Plate 18 ; with the 
condenser a stratified discharge and the tell-tale brilliantly illuminated, fig. 8, b. 
By charging up the condenser of 44'8 m.f. and allowing it to run down 
through the tube, it was ascertained, by measurement with the electrometer, 
that the current of 415 cells would just pass. 
The battery of 1080 cells gave a current of ’03754 weber in short circuit; 
the condenser employed in all cases was -g-th of G, Part I., page 99, having a 
capacity of about 0‘66 microfarads ; when brought into action, by pressing down 
the key K, fig. 41, there was no intervening resistance between it and the 
battery, and supposing it to be completely discharged automatically as soon as it was 
charged to the full potential, the current was sufficient to effect this 5 2 ’7 7 times in a 
second/'' To pass through the tube, however, the battery-current had to expend a 
certain amount of electro -motive force to overcome the impediments offered by the 
residual gas in the tube, and also the small resistance of the primary of the induction 
coil, so that the potential in the condenser might become somewhat higher than that 
necessary to overcome these impediments, and therefore from time to time an extra 
current from the condenser could pass through the tube, producing pulsations in the 
current through the primary of the induction coil, which are rendered evident by 
the glow in the tell-tale tube connected with the secondary wire of the coil. These 
* The time required to charge the condenser to the potential of 1 volt would be 0 . 03 ' 7 X 0’00000066= 
0 - 00001758 second, or it would be charged to the potential of 1080 cells (assuming them to be equal to 
volts) 52' 77 times per second. 
