320 Farwell — Wilson Tilted Electroscope. 



The top of the box was fully an inch over the heavy brass case 

 of the electroscope. 



The galvanometer, of low resistance, was fairly sensitive, 

 about 10 -9 amperes, and a resistance of 200 ohms was used in 

 series with the iron-constantin thermocouple. The electro- 

 scope leaf was not at its most sensitive position in this par- 

 ticular observation, the whole fluctuation being about the same 

 as would be caused by changing the potential of the leaf by 

 about '1 volt. 



By moving the position of the lamp to the other end of the 

 electroscope case, the leaf was observed to move down as the 

 temperature increased, showing that the direction of the con- 

 vection currents had been reversed. 



It would appear to be most desirable to use suspensions 

 adjusted as is the gold leaf in this case in a fair vacuum, since it 

 is generally necessary to use some sort of lamp to illuminate 

 the background for the leaf. 



Columbia University, 

 Jan. 29, 1914. 



