20 MM. E. du Bois-Revmond and W. Beetz on the 



Table XI. 

 Battery of Sixteen Elements. 



Coloured rings upon platinum. 



Table XII. 

 Battery of Six Elements. 



In these Tables we find an undoubted agreement of the 

 values tt.r 3 ; the radii of the external rings alone give different 

 results, and are not therefore made use of in calculating the 

 mean. These rings are denoted in the Tables by a star. Even 

 at the second light ring complete confirmation of the law of 

 the inverse cubic proportion of the radii commences. The 

 cause of the difference in the breadth of the above most exter- 

 nal rings is twofold. First, the entire calculation upon which 

 it is based depends upon the assumption that the anode is 

 an infinite plane. If this assumption is not satisfied, the curves 

 of the current deviate further from the rectilinear form, their 

 concave sides being turned towards the anode; thus the film 

 of peroxide of lead must evidently be of sufficient thickness, 

 even at a less distance than is expected from calculation, to 

 correspond to the required multiple of the quarters of the 

 length of the undulations of the yellow light, i. c. the radius 

 of the ring will be less. Secondly, the charge which the 

 plates acquire is not uniform throughout, but in the middle, 



