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PROCEEDINGS OF THE AMERICAN ACADEMY. 



The most interesting thing about the curve is the flat place which 

 occurs after 60-80 minutes of discharge. This is quite characteristic 

 of Plants plates with ribs, but it has never been noticed before by any 

 of the observers who have worked on storage cells. Indication of such 

 a flat place may be seen in some of Haagn's curves, but it would seem 

 that he thought them due to errors of measurement. 



Figure 5. Curves of resistance of Plante cell during discharge at various 

 temperatures. 



The reason for the appearance of such a change in curvature seems 

 quite obvious. These plates are of the Gould type, and they have 

 ribs spun from the lead of the originally flat plate. These ribs are 

 changed by formation to form active material, which lies close to the 

 ribs at their tops but which forms a solid mass down toward the center 

 web of the plate. During the first part of the discharge the electrolyte 

 finds active material on the ribs and diffuses largely into the almost 

 open space between them. As this material is used up the action 

 moves further into the plate and presently reaches the mass of material 

 which fills the bottom of the grooves. Here for a time there is mate- 

 rial enough at a practically constant distance from the surface of the 

 plate to supply the action, and when this is used up the resistance 

 rises very rapidly and the plate potential shows that the cell is com- 

 pletely discharged. 



