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PROCEEDINGS OF THE AMERICAN ACADEMY. 



be no doubt that the explanation given is the correct one. A similar 

 lag in the e. m. f. following a change in temperature is to be expected, 

 and this has been noticed by Dolazalek during careful determination 

 of the temperature coefficient of the e. m. f. of a lead storage cell. 



The curves of cell voltage during discharge are given in Figure 6, 

 and the flat place in the cui've is evident in all except the curve for 

 8.5°. It is possible that we missed it in this case by not taking points 



TABLE VI. 

 Complete Reversal at 2 Amperes. Temperature 8.5° C. 



close enough together, as it is quite evident in the curve of Figure 7, 

 which was drawn from another run at the same temperature. 



9. Two criteria have long been considered most pertinent as describ- 

 ing the condition of a storage cell. One of these is the density of the 

 electrolyte, and if care has been taken to keep this density right, it is 

 possible to judge accurately of the condition of the cell by an examina- 

 tion of the electrolyte at a given point in the cell cycle. Usually the 

 density is measured at full charge. It could as well be measured at 

 the end of discharge or at any other known point in the cycle, pro- 

 vided the curves describing the relation between density and voltage 



