170 
MESSRS. W. DE LA RUE AND H. W. MULLER ON THE 
Circuit. 
8600 cells 50,000 olims and tube 150 
„ 150,000 
„ 300,000 
„ 400,000 
500,000 
„ 600,000 
„ 700,000 
„ 800,000 
„ 900,000 
„ 1,000,000 
and liquid resistance 
more „ 
ig. 41), January 
28, 187 
c. 
V. 
2,300 
413 
1,260 
386 
787 
367 
625 
370 
518 
360 
435 
367 
374 
367 
331 
366 
291 
373 
267 q 
365- 
269 > 
373 
266 J 
369- 
203 
352 
40 
505 
43 
497 
50 
439 
31 
482 
35 
465 
17 
357 
The results for tube 31 are given in microwebers (millionths of a weber) and volts ; 
those for tube 150 are left in terms of the electrometer. 
By fixing small rings of tinfoil to the glass near the places where the metal terminals 
are fused into the tube and connecting these rings to earth, we were able to cut oft 
the leakage over the surface (which, in spite of precautions, is considerable,) and prevent 
it from interfering with our measurements of the potential of the gas inside the tube. 
The condition of the outside of the tube appears to have been the subject of much 
investigation by other observers : our experience points to the absolute necessity of 
cutting off leakage in order to obtain correct information concerning induced charges 
on the outside of the tube. 
In a paper published in 1870 (Proc. Roy. Soc. vol. xix. p. 237), Mr. C. F. Yarley 
stated : The following laws were found to govern the passage of the current : — 1st, each 
tube requires a certain potential to leap across ; 2nd, a passage for the current having 
“ been once established a lower potential is sufficient to continue the current ; 3rd, 
“ if the minimum potential, which will mahitain a current through the tube, be P, and 
the power be varied to P+1, P+2, &c, to P+n, the current will vary in strength, 
“ as 1, 2, &c. n. . . . It thus appears that a certain amount of power is necessary to 
“ spring across the vacuum ; after that it behaves as an ordinary conductor, excluding 
t; that portion of the battery whose potential is P, and which is used to balance 
'■ the opposition of the tube.” 
Laws 1 and 2 are confirmed by our daily experience, but the experiments which 
then led Mr. Vakley to the conclusion that, with a certain reservation, a “ vacuum 
