520 



Mr. E. C. Rimington on Luminous 



be longer than in the case of small ones. Now, as the initial 



value of -5- is the same whatever the size of the jars, the after 



values (although their time-integral is less and their actual 

 values less also) last longer in the case of larger jars. 

 When the breakdown of the dielectric of rarefied gas is once 



dc 



dc 



begun by the initial ^, the values of ~ necessary to keep it 

 up may probably be very much less, and consequently the 

 smaller values of -r lasting longer, as given by the larger 



jars, may produce a luminous discharge more brilliant to the 



dc 

 eye than the larger values of -r- lasting a shorter time, as given 



civ 



by the smaller jars. 



The actual results obtained with a ring of four turns of wire 

 containing an exhausted bulb about 2 J inches in diameter 

 were that the differences in brilliancy, obtained by using 

 half-gallon jars, pint jars, or very small jars made from spe- 

 cimen glasses, were not so very great. 



Other Effects. Apparently unclosed Discharges. 



A closed luminous discharge is not the only one that can 

 be obtained. Mr. Tesla, in 1891, pointed out that by wrap- 

 ping a wire round an exhausted tube so as to form a coarse- 

 pitched spiral, a luminous spiral discharge is obtained. He 

 was apparently only able to obtain a very feebly luminous 

 spiral, but the author has succeeded in getting one quite as 

 brilliant as in the case of the ring-shaped discharge obtained 

 with a bulb. 



Fiff. 10. 



In fig. 10 two half-gallon jars have their outer coatings 

 connected by a wire, A B, bent as shown in the figure. Over 



