498 
MESSRS. W. DE LA RUE AND H. W. MULLER ON THE 
the centre ring No. 9 to earth, the deflections, as we have before said, were all positive 
between 1 and 9, and all negative between 9 and 17 ; if the connexions with the 
battery were made previous to the connexion of 9 to earth, and a well-formed steady 
stratification produced, very little change occurred in it when 9 was connected by 
me ns of a key to earth; in fact only a slight one in those strata close to the earth 
ring. 
The curves, more especially fig. 21, show that there is no disturbance of the 
potentials in consequence of the earth connexion in the centre of the tube, but that 
the whole curve is lifted or depressed so as to cut the axis at that point, 1 lie curve 
(fig. 22) brings out very forcibly how far greater is the obstacle to the passage of the 
discharge at the negative than at the positive electrode. 
We have already called attention in Part III. of our researches to the far greater 
obstacle presented by the negative terminal to the passage of a discharge than occurs 
at the positive.* We therein described an experiment with a tube in which the 
negative terminal was a wire 19 inches long which became more and more illuminated 
as the current was gradually increased. 
Fisr. 21. 
In order to bring into strong evidence the great resistance to the passage of elec¬ 
tricity at the negative as compared to the positive terminal, the same ring was made 
positive and negative alternately. 
* Phil. Trans, for 1880, vol. 171, Part I., p. 108 (separate copy, Part ITT., p. 202). 
