1879.] On Electrical .Discharges through Rarefied Gases. 23 



The effects above described need not be confined to a single patch 

 or ring of conducting material placed upon the tube ; but they may 

 be produced many times over in the same tube by a series of rings 

 arranged at suitable distances. By this means the column may be 

 broken into a series of sections, all terminating with well-defined con- 

 figurations towards the negative end, and having greater or less 

 length, according to the position of the rings. In the paper itself, 

 arguments are there brought forward showing that these sectional 

 discharges represent striae not merely in their appearance, but also 

 in their function and structure. But the discussion could hardly be 

 produced within the limits of an abstract. 



Returning from the digression about striae, the authors next give 

 evidence, derived mainly from the revolving mirror, and from the 

 discharges of a partially charged Leyden jar, for the following con- 

 clusion : That the passage of the discharge occupies a time sufficiently 

 short ill comparison with the interval between the discbarges to 

 prevent any interference between successive pulses. Certain experi- 

 ments are then described which indicate that the discharge is effected, 

 under ordinary circumstances, fry the passage through the tube from the 

 air-spark terminal of free electricity, of the same name as the 

 electricity at that terminal. In the case of an induction coil, where 

 the air-spark must be considered as existing at both terminals, there 

 is evidence of a neutral zone, where the sensitiveness disappears. The 

 position of this zone may be altered by damping the impulses at either 

 terminal; or it may be abolished by connecting one terminal with 

 earth. The impulses may even be so distributed as to divide 

 electrically a single tube into three sections, the two extremes pre- 

 senting visible discharges, with a dark section between them. 



Looking at all these phenomena from an opposite point of view, 

 we may, by means of the relief effects, determine the terminal from 

 which a discharge proceeds, and the distance to which it reaches 

 without provoking a response from the other. And through these 

 considerations, together with others detailed in the paper, the authors 

 are led to the conclusion that the discharges at the two terminals of a 

 tube are in the main independent, and that they are each determined 

 primarily by the conditions at their own terminal, and only in a 

 secondary degree by those at the opposite terminal. 



In illustration of this view, an account is then given of the pro- 

 duction of unipolar, positive, or negative discharges in a tube. In 

 such cases, the discharge being insufficient of itself to pass through 

 the tube, returns by the way by which it entered. 



This closes a series of experiments, the result of which is that the 

 discharges from the two terminals can be made of equal intensity, or 

 of any required degree of inequality ; or the discharge can be made 

 to issue from one terminal only, the other acting only receptively ; or 



