﻿Electrical Changes induced by Ultraviolet Light. 415 



measurements it gives the same initial value on recleaning, 

 but the subsequent rate of tiring differs from that o£ the 

 previous experiment; the breaks are obtained but they are 

 much less persistent, and the rate of tiring is very much 

 accelerated. The increase in the rate of tiring is more 

 noticeable in each successive series of experiments. Six 

 series were made with a magnesium plate at various intervals 

 of time, and these show very well the breaks and the in- 

 creasing rate of retardation of the discharge (Curves L, II., 

 III., IV., PI. VI.). The two series between II. and III. were 

 spoiled. The numerical results are given in Table X. 



Table X. — Magnesium. 



It will 



1 

 I. 



IT. 



III. 



IV. 



18 May. 



13 June. 



21 June. 



18 July. 



Leak in 



Exposure 



Leak in 



1 



Exposure 



Leak in 



Exposure 



Leak in 



Exposure 



sees. 



in miiis. 



sees. 



in mins. 



sees. 



in mins. 



sees. 



in mins. 



























17 



6 



2-2 



10 



1-0 



0-4 



1-7 



02 



42 



L-6 



26 



1-6 



1-8 



1-2 



2-8 



1-2 



6-8 



30 



4-2 



24 



32 



2i> 



3-6 



2-4 



B-2 



4-4 



54 



4 2 



4-8 



3-6 



53 



38 



129 



5-4 



73 



6-2 



66 



54 



74 



(',••. 



132 



70 



8-5 



92 



85 



7-8 



7-4 



9-2 



171 



90 



100 



130 



100 



10-2 



98 



120 



180 



IIS 



10-8 



192 



110 



134 



106 



160 



191 



150 



117 



264 



125 



18-4 



12-5 



210 



197 



17-8 



12-5 



360 



130 



23-8 



130 



252 



211 



20-4 



136 



46(i 



148 



32-0 



136 



30-2 



22-4 



250 



134 



61-4 



155 



442 



141 



370 



20-4 



29-4 



141 



85 



LV4 



53-0 



150 



454 



22-4 



34-4 



135 



1048 



15-4 



716 



14-8 



53 



22 1 



39-8 



13-8 



123-6 



15-4 



88-6 



17-1 



654 



224 



466 



140 



145-9 



161 



114 



192 



79-0 



22-4 



55-6 



16-0 



200 



176 



164 



23 



92-0 



231 



66-4 



168 



233 



19-0 



211 



21-8 



110 



252 



75-4 



19-4 



258 



19 8 



247 



; 2L8 



146 



25-2 



830 



20-0 



319 



20-3 



297 



31-6 



190 



25-5 



970 



19-8 



397 



202 



' 336 



36-4 



243 



28-2 



122 



194 



458 



22-4 



388 



45-2 



288 



30-6 



149 



19-4 



533 



27-2 



461 



733 



330 



37-4 



176 



230 



656 



230 



526 



87-6 



381 



41-5 



202 



193 



720 



3S"8 



563 



108 



428 



460 



! 229 



760 



1440 



406 



627 



131 



470 



600 



•-o9 







472 



689 



141 



525 



750 



298 







76-2 



828 



292 



615 



89-0 



339 







251 



1428 



439 



692 



126 



379 











665 



758 



166 



455 











981 



1418 



207 

 269 

 375 



584 

 1424 



533 

 580 

 642 

 798 

 1450 



