446 Mr. Garrett and Dr. Willows : Chemical 
The curves in fig. 6 are plotted from these numbers. 
They resemble the figures given by H. A. Wilson* for the 
Fig. 6. 
200FP TTT TT eee 
SERRE SERRERRERERE ERR ESRRREREREREEPRERRPE SRST 
PRIRMEREEREREARERER SHAE RSRESRIRRKERRESEESEE 
AES PARES EREARRPOLE PRERRRERRESEREE VER EERE 
EERSRS SCARE ERRRRSES SRRERRAURRRRRASRERRESRAEDS 
7 SEER ARERR RRRERRERREESRERERRRRBRRERRAREEERERESESS 
gen a SERESERREREREEEY.. 
EERE ERERERERARAALAARERABREREEREDEAGEKELBLSeS 
450 
a a 
see COOOL OCC 
PT tr er) 
PC ae 
FAME RERNENREBERES SS 
# SRS ER RREREREE”. GABERRERRERSRPLS SS 
BHRRRESHAS? AHRERRTORRBSRRSEPURARAPARRRAREASSS 
SERBRERERD CRUST ERORE pt BERERRREEIHeS 
- BRSRSRE AL ALLA B.. ABERRERARERSRARAREAP SS. 
50 eae 
< SHSEE).ABGOS | Be arReaee ae BEREESEUA ) 
uw AL “ ptt BERERRRRRESAS 
od RRB aH r¢ a BERSERERERRS SC. 
Ree Tee, SOUR eEH 
eer Tee ee 
SE) SRESESRREEAE GRRE VERE SERRE RARERNANA 
Se ee eee ee eee 
7 Sgermaaeh enue Wee Ea NEUES ESEEE EUCSECEESS ES EEETETE 
ie Bs PLP eT ea eee 
80 460 240 320 400 
VOLTS 
case of the current between a hot platinum wire and a hot 
platinum tube outside it. When the current is carried by 
positive ions (C negative) no evidence of a saturation value 
is evident: this is most probably due to their small velocity, 
which renders it difficult to drive them out from the thin 
layer in which they are produced. The negative ions moving 
more quickly, are more easy to remove. _ 
Another explanation may, however, be given. Prof J : 
Thomson advances the opinion that the emission of negative 
corpuscles (or electrons) from heated substances is a general 
property of the atomy. An experiment with sodium vapour 
is given as an instance where the emission takes place at a 
temperature as low as 300°. If the negative 1ons are pro- 
duced in this manner in the present instance, they would be 
more or less distributed throughout the space between the 
electrodes. In that case, itis known that a saturation-current 
* H. A. Wilson, Phil. Trans. A, cxevii. p. 415 (1901). 
+ «Conduction through Gases,’ p. 168. 
