104 Prof. Millikan and Mr. Winchester on Influence of 



The observations shown in this table covered a period of 

 about two days. It will be seen that the readings are not 

 very satisfactory from the standpoint of the agreement 

 between observations taken under apparently identical con- 

 ditions, and it was for this reason that the results were not 

 published at the time. Nevertheless, the table is sufficient to 

 show clearly that within the limits of the rather large obser- 

 vational error, temperature has no effect whatever upon the 

 rate of discharge of electrons from aluminium, at least, within 

 the temperature range 50° C. to 343° C. 



Observations could not be carried much aboA r e 343° C, for 

 the reason that between this point and 400° C. the natural 

 leak of the system, consisting of the electrode and the elec- 

 trometer, became so large as to mask completely the effect of 

 the ultra-violet light. In fact, at 400° 0. the electrometer 

 would lose either a positive or a negative charge with equal 

 readiness, and so rapidly that the needle returned to zero in 

 approximately the same time as when it was connected to 

 earth. This leak disappeared as soon as the temperature was 

 again reduced to about 340° C. 



5. Experiments upon other Metals. — In order to obtain 

 observations upon a whole series of metals under identical 

 conditions, the tube shown in fig. 2 was constructed. Within 



Fig. 2. 



\ To - 



m 



1 t~j 



El £s — 4 — Wmk> 



a glass bulb 8 cm. in diameter an aluminium wheel, W, 

 6 cm. in diameter was mounted upon agate bearings a. At 

 equal intervals about the rim of this wheel were screwed 

 metal disks, c/, 1 cm. in diameter, of copper, nickel, iron, 

 zinc, silver, magnesium, lead, antimony, gold, aluminium, and 

 brass. To the Avheel was also attached a small strip of iron 

 to serve as a magnetic control, so that with the aid of a large 

 magnet outside of the tube any desired disk might be rotated 

 to a position in line with the beam of ultra-violet light which 



