66 



A CONTINUOUS RECORD OF ATMOSPHERIC NUCLEATION. 



The occuiTence of different slopes in the curves is an obvious result of the 

 unavoidable differences of initial nucleation. The effect is a shifting of the z 

 values. Thus in two series for the same corona similarly observed, but ^^-ith 

 independent initial nucleations, r^r^i — az)=r'a{i — a'z'), Avhere z' = z—z'^; 

 whence n' = a/(i — az'^), the constant 0',, being the index of the difference of 

 initial nucleations. 



A computation on the assumption of constancy of a was made for com- 

 parison, and is given in the preceding table, 3, corresponding to table i above, 

 and with the same notation. 



II. Exhaustion loss attributable to subsidence. — The misleading feattu^e of 

 a is its apparent constancy for a given receiver and a given scheme of obser\^a- 

 tions. It will now be shown that this result is a mere approximation and that 

 the phenomenon may be fully explained in terms of subsidence. In this case, 

 10* R = g i/Y', where R is the radius of the water particle and v its rate of stib- 

 sidence. Since 2 R = d= .00^2/s, approximately, v= (i.'j8)'/s% or ii v' refers to 

 minutes, t;'= 190/5'. 



The relative loss, /, per minute, is for a vessel of height h and nucleation 

 n, l = v/h='igo/hs\ If, as in the above condensation chamber, the height is 

 /j = 26.5 cm., /= 7.2/5', or, in tabular form. 



I 

 7.2 



2 

 1.8 



.80 



•45 



.36 



numbers which are astonishingly large, but must be near the truth. 



Let the time consumed in observation be 1/2 min. and 1/4 min., respect- 

 ively; then the ratio r in table i may be corrected in the region of normal 

 coronas as follows: 



TABLE 4. — CORRECTION OF i=27ss'/io'''^^ IN TABLE 3, SHOWING THE EFFECT 



OF SUBSIDENCE. 



The first of these values of r is under-corrected, while the second r is over- 

 corrected. The mean of these corresponding to a time of observation of | 

 minute is constant. Now as the time during which the fog is left undispelled 

 after exhaustion for measurement is actually of this order, there can be no 

 question but that the error is due to subsidence. The equation should therefore 



read: 



w = Cs^ = n^ 10- '"*■'•'' (i — 5/5-o)(i — 5/5-\). . . 



