562 Mr. G. Jaffé on the Conductivity of 
big vessels of several litres capacity are far less pronounced 
than those in small vessels of about 100 c.cm. capacity. 
Some experiments carried out by the electroscope-method 
with a vessel of about 10 litres volume confirmed this fact, 
which seems to indicate that the cause for these variations 
depends on the surface and not the volume of the vessel. 
All experiments mentioned so far were made with air 
which had been for a considerable time within the vessel 
where its conductivity was to be measured. The question 
whether the leak alters when the air is replaced by fresh air 
has not been dealt with. Now it is known by the original 
measurements of Geitel * that the leak during the first four 
days after filling the vessel with fresh air increased to about 
five times its initial value. C.T.R. Wilson does not mention 
the same fact, and as Geitel used a very much bigger volume 
(13,000 to 163 c.cm.) it seemed likely that it is confined to 
large vessels. ‘This is, however, not the case ; an increase of 
the initial conductivity can also be observed in the case of 
small vessels of silvered glass, though it is far less pronounced 
than in Geitel’s experiments. Indeed, the change is very 
slow, and was therefore not noticed until it was found that 
the leak in a vessel is always too big, after it has been left 
for some time to itself. ‘This point was further examined, 
and it was found that the leak after refilling the vessel in- 
creased in some cases by 25-35 per cent. in 5 to 7 days and 
then remained constant, or at least oscillated round a constant 
mean. 
The behaviour was, however, by no means consistent in all 
cases ; sometimes the increase went on for a far longer period 
and sometimes the total increase did not exceed 20 per cent. 
Table IV. contains average leaks for two different bulbs 
during the first 7 to 9 days after refilling them with fresh 
air, the units are arbitrary. The table will show the irre- 
gular nature of the increase. 
TABLE IV. 
ay... Ist | 2nd | 3rd | 4th | 5th | 6th | 7th | 8th | 9th | 16th 
Bulb I. \ 10-8] 11:5) 12-4| 12-2] ... | 12-31 12-6 
97 c.c 
P 10-0] 10-0) 10:4] 10-7] ... | ... | 11-6] 12-0 
10-0] 10-2] 10°6| 11-01 ... | ... | ... | 11-4 
Bulb II. | 10-2] 10-3! 10:3] 10-8| 10-9! 10:8] 10-9 11-0! 11 1] 123 
59 ec.e.. 
“ 10-3] 101] 11-0] 12:8] 13-1] ... |... | 13-1) 13°3 
_& Physikalische Zeitschrift, ii. p. 116 (1900). 
