a Source of small Constant Currents, 

 Table II. (continued). 



363 



Date. 



Time. 



A. 



-Resistance between Poles. 



1888. 

 Aug. 21. 



(10.) 



h m s 

 4 12 



12 45 



13 20 

 15 



15 



16 



volts. 



0-000000 



+0-004636 



+ 0-004591 



+0-004551 



Changed from oo to 1423 1. o. 

 1423 

 1423 

 1423 



Changed to oo . 



CO 



+0-000045 



Aug. 21. 

 (11.) 



4 19 

 19 15 

 21 



21 



22 



0-000000 

 +0-004641 

 + 0-004551 



Changed from oo to 1423 1. o. 



1423 



1423 

 Changed to oo . 



00 



+0-00009D 



Aug. 21. 

 (12.) 



4 25 



25 40 



26 10 

 28 

 28 

 28 20 



0-000000 

 + 0004546 

 +0-004505 

 +0-004505 



Changed from oo to 1423 1. o. 

 1423 

 1423 

 1423 



Changed to oo . 



CO 



+0-000135 



Aug. 21. 

 (13.) 



4 30 

 31 

 36 



36 



37 



0000000 

 +0-004551 

 +0-004551 



Changed from oo to 1 423 1. o. 

 1423 

 1423 



Changed to oo . 



00 



+0000135 



The scale of the curves is very big in order to bring out 

 differences of observed values of A ; it will be noticed, how- 

 ever, that A was in all cases extremely small. 



The general effect is seen to be a decrease of A as time 

 goes on from the epoch of short-circuiting. This has already 

 been discussed. For comparison a large Daniell cell was 

 examined at the same time, and the dotted curve in Plate XIII. 

 referring to it will show its unexpected inferiority. The cell 

 exposed about 80 square inches of copper, and was allowed 

 to work long enough to obtain a clean electrolytic surface ; 

 zinc- sulphate solution was used in the inner cell. The resist- 

 ance of the cell was very low, and the curve taken is for its 

 behaviour when short-circuited through 143 1. o. This gives 

 a current of about - 0067 ampere ; and a current-density of 

 O000012 ampere per square centimetre of copper. In the 

 large Clark cell the curve for a current of about 0*01 ampere 

 (condemning the cell for so great a current) corresponds to a 



