392 Barus and Watson — Air Stored over Water. 



Art. XXXYIII. — On the D enucleating Effect of Rotation in 

 case of Air Stored over Water ; by C. Barus and A. E. 

 Watson. 



1. The following interesting result was obtained incidentally, 

 in connection with other researches. 



If air containing nuclei from any source whatever is intro- 

 duced into a cylindrical condensation chamber over pure water, 

 and if the cylinder is rotated on its axis more or less rapidly, 

 without further interference with the air contained, the charge 

 of moist air will soon be found to be free from nuclei. 



2. The following are examples of the results obtained. 

 Nuclei were produced in dust-free air by passing the X-rays 

 through a cask of paraffined wood, in the direction of an equa- 

 torial diameter, for three to five minutes. The cask was 35 cm 

 in diameter and 40 cm long, mounted axially on an axle and 

 turned by a small electromotor. The coronas were viewed 

 through two longitudinal and diametrically opposite strips of 

 plate glass. Details of construction cannot be considered here ; 

 we need merely state that the apparatus during rotation was 

 absolutely free from leakages of nuclei, either of efflux or of 

 influx. 



The size of the corona due to nuclei generated by the 

 X-rays is unfortunately very variable, depending (caet. par.) on 

 conditions of radiation beyond the observer's control. Diame- 

 ters ranging on an arbitrary scale from 6 to 12 cm were obtained 

 for the case of rather weak radiation, passing for three to five 

 minutes through the wood of the stationary cask. As a rule, 

 the nuclei vanish in less than three minutes of moderately fast 

 rotation (two turns per second), and the corona obtained there- 

 after is almost too weak for detection. At these speeds the 

 whole of the water does not yet adhere as a smooth cylindrical 

 apparently rigid sheet to the sides of the cask, but is carried 

 around with more or less turbulent motion. 



Table I. — Number of nuclei, n, per cub. cm. before and after rotation. 

 Pressure difference about 22 cm . Nuclei produced by X-rays to the aver- 

 age number of 30,000 to 70,000 per cub. cm. 



Arbitrary 

 Experiment Time of Time of Turns diameter n nuclei 



No. radiation, rotation, per min. of corona. per 



min. min. cm. cub. cm. 



1 3 4-1 27000 



— 2 140 1-8 2500 



— 4 140. -0 



4 5-6 69000 



500 



2300 

 



3600 

 50 











5-6 



6 



120 



1-1 











1-8 



3 



64 



•o 











2-1 



3 . 



230 



•5 



