On the Luminous Discharge of Voltaic Batteries, 543 



facilities at command, but a thoroughly well-insulated battery of 3000 

 or 4000 series would produce effects well worthy of examination. 



Fig. 3 B. 



BanieWs Constant Battery. 



On the 27th of December, 1859, by the introduction of Professor 

 Wheatstone, I had the opportunity of experimenting with the large 

 battery belonging to the Telegraph Company at its Factory, Camden 

 Town; Messrs. Wheatstone, Latimer Clarke, and Bartholomew were 

 present. My object was to ascertain whether a luminous discharge 

 could be obtained through the vacuum-tubes from the battery, which 

 consists of 512 series of Daniell's elements, zinc and copper. The 

 zinc plates are 2 by 3| inches, the copper 3| by 3| inches ; the cells 

 are insulated in series of 10 and 1 2, suspended on trays by gutta-percha 

 bands. I experimented with three of my vacuum-tubes, Nos. 187, 1 96, 

 and 219, with 187 and 196 ; no sign of any luminous discharge could 

 be observed ; the electroscopes (Peltier's and a gold-leaf), by the 

 tension, showed that the current did not pass. 



With 219 the brilliant glow around the negative ball, as is shown 

 in the same tube by the induction coil, was visible with very trifling 

 luminosity on the positive. I have attempted to show this appearance 

 in fig. 3 A. 



Various lengths, viz. 110 yards, 1, 2, 4, 8 and 16 miles of covered 

 copper wire, the 110 yards covered with india-rubber, and the other 

 lengths with gutta-percha, are kept immersed in a water-tank for the 

 purpose of experiments at the factory ; an opportunity was therefore 

 offered of testing the action of the battery on these wires by means 

 of vacuum-tubes. This immersed wire is designated the cable, acting 

 in this respect in a manner analogous to submarine wires. 



The general results obtained, and repeatedly verified, may be 

 briefly stated as follows : — From the 110 yards to the greatest length 

 of 16 miles, it took from half to one and one quarter of a second for 

 the cable to receive as much of the charge of the whole battery as 

 could pass through the vacuum-tube 219, the time being denoted 

 by the appearance of the luminosity in the negative ball (see fig. 3 A). 



With 110 yards the discharge of a charge previously given to the 

 cable was instantaneous ; it appeared to be nearly momentary with 

 one mile, and the time then progressively increased according to the 

 length of the cable previously charged, until with the 16 miles it 

 took one and a quarter to one and a half seconds before the luminous 

 glow on the ball in the vacuum-tube disappeared. 



It was beautiful to see the regularity with which the glow appeared 



