ALTERNATIONS OF APERTURE. 



the filter. Periodicity thereafter fails to reappear, as is also the case in 

 parts Viand VII. Similar cases occur in parts VIII, IX, and X. The 

 mean apertures at 25, 20, and n do not differ sufficiently to indicate 

 a temperature effect above the value of the incidental errors. 



TABLE 10. Periodicity in the condensation of dust-free air. Plug valve. Pressure 

 difference, 8^=31.2 cm. Temperature = 25 C. Glass clear, no shaking of 

 water needed. Two-minute periods between exhaustions. Slow influx. Cylin- 

 drical fog chamber, volume ratio v\V ' = 0.063. 



* After i6 h (left over night). t After 25 m . 



^Accidental rapid influx. Note the rise of inferior coronas. 



TABLE 10, continued. Slow influx; water shaken; fog in glass; 20 C.; 



31.2. 



Left after i5 h . f Periodicity absent in the first case after accidental influx. 



