Discharges in Electrodeless Vacuum-Tubes. 523 



A ring (R) of four turns of wire is joined in series with a 

 single turn, and the two are connected to the outside coatings 

 of the jars. In the single turn a bulb is placed and the spark- 

 gap adjusted until a fairly bright ring is produced in it at 

 every discharge. If now a closed ring of thick copper-wire, 

 a metal plate, or a ring of several turns, similar to R, and 

 with its ends joined, be laid on R to act as a secondary, the 

 luminous ring in the bulb is brighter ; on substituting for this 

 an exhausted bulb and placing it in R, there will be a brilliant 

 ring-discharge in it, while the discharge in the other bulb 

 will be rendered fainter or altogether extinguished. In this 

 experiment the exhausted bulb secondary appears to act in 

 the reverse way to a metallic secondary. 



The author then made the following experiments : — 



(a) A ring of four turns of guttapercha- covered wire pre- 

 cisely similar to R was made, its ends were connected to an 

 ordinary Geissler tube. When this was used as secondary it 

 acted exactly in the same manner as the exhausted bulb both 

 in the first and second experiments, the Geissler tube being 

 brilliantly illuminated. 



(6) The Geissler tube was then removed, and the ends of 

 the secondary coil connected to the coatings of a small Leyden 

 jar. The effects produced by this secondary were the same as 

 those produced by the exhausted bulb in both experiments. 



(c) The ends of the secondary were connected to the loops 

 of aglow-lamp to act as a resistance (about 100 ohms). This 

 acted similarly to the exhausted bulb in both experiments. 



(d) A disk of gilt paper (imitation) and also a ring of the 

 same were used as secondaries ; these acted similarly to the 

 bulb in both experiments. When the discharge took place 

 there were brilliant sparks produced at various spots on the 

 paper, wherever there was any flaw in the gilding, showing 

 that considerable energy was dissipated there. 



(e) The secondary coil of four turns had its ends joined by 

 a strip of gilt paper about 6 inches in length, with a con- 

 siderable number of flaws in the gilding (produced purposely, 

 by bending the paper sharply in several places, so as to 

 obtain considerable sparking). This acted similarly to the 

 bulb and dimmed the discharge in the bulb surrounded by the 

 single turn. On shortening the length of gilt paper between 

 the ends of the secondary, the discharge in the bulb was less 

 dimmed. 



The results of these five experiments are, that any of tho 

 above secondaries are able to reduce the mutual induction 

 between the primary and secondary in the first experiment 

 sufficiently to render faint or altogether extinguish the 



2 2 



