342 C. Bar us — New Method for Standardising the Coronas. 



Art. XXXIII. — On a New Method for Standardizing the 

 Coronas of Cloudy Condensation y by C. Bartjs. 



Assuming that for ions produced within the fog chamber 

 the rate of decay in the lapse of time t is as the square of the 

 number, or that 1/n — 1/n' = b(t—t') where b is constant, a 

 few incidental attempts were made to compute b, when the 

 number, n, of nuclei (ions) is expressed in thousands per cubic 

 centimeter. The table gives an example of such results, 

 obtained by exhausting the fog chamber at a stated time t, after 

 the removal of radium. If the drop in pressure is below the 

 coronal fog limit of air, precipitation takes place on ions, 

 only. 



Table. — Decay curve. Nucleation observed and computed, b = -0024 

 relative to n x 10— 3 . Eadium suddenly removed from top of fog chamber 

 (glass) and exhaustion made t sec. thereafter, dp = 23 cm (below the coronal 

 fog limit of dust free air), s/30 (nearly) angular diameter of coronas. 



(Computed for 



t 



s 



(observed) 



b — -0024) 



sec. 



cm. 



n x 10- 3 . 



n x 10 — 3 . 







5'9 



67 



67 



5 



5-0 



41 



37 



10 



4*6 



32 



26 



15 



4-0 



21 



20 



20 



3'5 



15 



16 



30 



3 3 



12 



12 



50 



2-9 



7 



7 



120 



1-7 



2 



3 



CO 



1-0 



1 





For the first five seconds b — "0019 ; for the first fifteen 

 seconds b = '0022; etc., values obtained ranging from -002 to 

 •003. This is larger than the corresponding electrical datum, 

 say '0014, when n is given in thousands. Decay is more 

 rapid than the equation warrants. Initial coronas are too 

 large, final coronas too small, in spite of the presence of air 

 nuclei, the number of which should be deducted, at least in 

 part. Other experiments show similar coefficients. Natur- 

 ally the present method for b is much inferior to the electrical 

 method, even if the two coefficients are identical ; and the b 

 here is obtained under possible complications with the larger 

 gradations of the colloidal nuclei of dust free air, though these 

 are probably inefficient. 



If the values of 1/n be inserted the curves should be linear 

 since 1/n = l/n -f- bt where t is the time dated since the 

 occurrence of ?i . The line passing through the observations 

 at 5, 30, 50 seconds is best adapted to represent the results, and 



