244 



DISCHARGE OF ELECTlilCITY, 



direction ; it is impossible to get a discharge through a tube of this 

 kind. 



h'w. it. 



On the other hand, the molecules exhibit remarkable powers of mak- 

 ing closed chains for themselves when not actually prevented 

 by the action of the electro-motive intensity. Thus the dis- 

 charge will pass through a great length of tubing in the 

 secondary, even if it is bent up as in Fig. 10, where tlie ver- 

 tical piece in the upper part of the secondary is at right 

 angles to tlie direction of the electric force, and where the 

 molecules will receive no help in forming closed chains from 

 the action of the external electro-motive forces. I have c- 

 ceeded in sending discharges through tubes of this kind V2 

 to 14 feet in leuirtli. - F\a. w. 



Screening effects due to the currents in the tubes. — One very noticeable 

 feature of these discharges is the well-defined character of the ring, if 

 the pressure is not too low. If a large bulb is used for the secondary 

 with the primary just outside it, when the sparks 

 pass between the jars a bright, well-defined ring 

 passes through the bulb near to the suri'ace of the 

 glass, the gas inside this ring being, as far as can 

 be judged, quite free from any discharge. If now a 

 bulb whose diameter is less than that of the lumin- 

 ous ring is inserted in the primary in place of the 

 larger bulb, a bright ring will start in this, though 

 at this distance from the primary there was no dis- 

 charge in the larger bulb. Thus when the large 

 bulb was in the primary, the discharge through its 

 (mter portions screened the interior from electro- 

 ■Jb^a/^ motive forces to an extent sufficient to stop a dis- 

 ^'*''^' (;harge which would otherwise take place. 



The screening action of these discharges is also shown by the follow- 

 ing exi)eriment: A, B, C, Fig. 11, is the section of a glass vessel shaped 

 like a Bunsen's calorimeter; in the inner portion A, B. C of this vessel 



