

MR. DE LA RUE'S BATTERY. 97 



before actual contact is made between the poles. We all know that 

 when once contact is made, and the poles are afterwards parted, 

 a beautiful arc of light, the voltaic arc, passes between the terminals, 

 and the action is then continuous. He obtained some very beautitul 

 results, with the discharge of the voltaic battery in residual vacua in 

 tubes pretty nearly exhausted of the gases which they contained, and 

 was one of the first, I beleive, to observe the stratification which 

 takes place in these discharges. In a tube connected with the poles 

 of a battery, or with the secondary wire of a Ruhmkorff coil, the 

 discharge is sometimes continuous as a sheet of nebulous light, 

 but mostly is beautifully stratified, and these stratifications we find to 

 be different for different tubes. There has been no incontestable 

 explanation yet given of the cause why we should have intervals 

 of light and dark in the electric discharge in vacuum tubes. Mr. 

 Gassiot carried on for many years a number of experiments, latterly 

 with 3500 Icelandic cells, with a view to elucidate the theory, and 

 .since he has in a manner relinquished them, I have taken up the 

 .subject in conjunction with my friend Dr. H. W. Miiller. We have 

 now 5,640 cells at work, and are adding 2,400 more, which will be 

 at work in a few days.* If I could have had wires laid here from my 

 laboratory, I could have repeated many instructive experiments. We 

 have obtained some very curious results, which will form the subject 

 of a communication to the Royal Society. The number and form of 

 the strata varies, depending first of all on the individual tube, and the 

 nature and tensions of the gases it contains, and also on the electro 

 motive force of the battery and resistance interposed in the circuit' 

 One may make the number of strata greater or less. Generally, if one 

 introduces very great resistance their number augments, and as one 

 takes out the resistance they diminish in number, and their width 

 becomes greater, but this law does not always hold good, for there are 

 .some tubes which behave in exactly the contrary manner. But there 

 is one point that I wish to bring particularly under your notice, and it 



* 8,040 cells have been completed since this discourse, part of them, 3,240, have the 

 chloride of silver in the form of powder, and are not so energetic as when it is in the form of 

 a rod fused on to the silver wire. The striking distance of 8040 cells between a point (positive), 

 -and a plate one inch in diameter (negative), is 0.345 inch rather greater than one third of an 

 inch. 



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