142 



VAPOR NUCLEI AND IONS. 



lenses or moved to a reasonable distance away from the window during 

 the passage of the air to be tested. In winter all measurements must be 



made with a galvano- 

 scope on the outside of 

 the house. Thermome- 

 ters are shown at T. 



The difficulties encoun- 

 tered in using this ap- 

 paratus in cold weather 

 will be investigated later 

 (section 94). Here some 

 reference to its constants 

 is in place. The quantity 

 of air passed through the 

 condenser in the fiducial 

 time (about 10 minutes) 

 was 1.0357 X io 9 cubic 

 centimeters; the capacity 

 of the condenser 17.74 



Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Cffl. Hence if V is the 



Fig. 63. -Atmospheric nucleation (thousands per cubic dr P of Potential in volts 

 centimeter) from October, 1902, to March, 1906. during the fiducial time 



specified, 



~ F/300 V 

 Q= 1 7.7 _ - = 



1.0357X10 8 17.52X10 6 

 denotes the charge in 1 cubic centimeter of air. As 3 



4 X 



ro l0 is the 



electrostatic charge per electron, 



wXio 3 = =, nearly, 



3.4Xio~ 7 6 



shows the number of ions per cubic centimeter. Measurements to find 

 their velocity were not made, as this would have carried me too far from 

 the purposes of this paper. 



I may add that a similar apparatus was installed, in which the winter 

 indraft of cold air (through a condenser), measured by an anemometer, 

 was utilized. The object here was to determine the hourly variations 

 of ionization. Though many observations were taken, their meaning is 

 vitiated by the temperature discrepancy mentioned in section 94. For 

 this reason, perhaps, a periodicity similar to the one discovered by Wood 

 and Campbell (Nature, April, 1906, p. 583) with stagnant air was not 

 detected. 



