298 



A new storage battery "duro,"' iiiade liy the Chicago Battery Co., was 

 iised and showed no variatious in E. M. F. dnriug the entire time. 



The density of the oil was determined by a speeitic gravity bottle and 

 fonnd to be .8370. 



The temperatures were read on a standard thermometer graduated to 

 1-10 degree. 



As to the question of the accuracy of the thermo-couple in registering 

 the instantaneous temperature we have to consider the couple itself, its 

 behavior under known conditions, and the results obtained. 



The couple was of Fe-Cu, one millimeter in diameter, so its heat ca- 

 liacity was very small. In calibrating it a deflection was regularly noted 

 when the change of temperature of the bath was less than ]-100 of a 

 degree. It was found that for small changes in temperature considerable 

 time, several seconds, elapsed before there was any heating due to radiation, 

 etc. This was due largely to the size of the vessel. Using a smaller one 

 tlje time required to warm up was small. 



The experiment is now being repeated under vastly better conditions. 

 The temperature of the bath is regulated by an electric thermostat, the 

 resistances, barometer and thermometer, have been checked up by the 

 Bureau of Standards at Washington and the voltage of the "duro" cell tested 

 immediately before and after each observation, by means of a potentiome- 

 ter of the Leeds Northrup type and a standard Weston cell. The results 

 from the new determination will bp iiuiilislicd later. 



Wahash College, 



CrairfordsviUr, fud. 



