98 VAPOR NUCLEI AND IONS. 



This may be written 



i Cd (dn/dt) 

 2\/&J (dn/dtWa- dn/dt 



from which, after integration, 



-2\/ab- t + c^N-s/a/b 



N+Va/b 

 If 



n n x . 2bn 1 t 



=Ae 



nXn 1 



where A is a constant and n A = \/ a /b, 



i+Ae- 2bn ^ 

 n = n 1 r - 



If /= oo , n = n t , a = bn 2 , which is otherwise evident. The coefficient 

 a is here taken as an absolute constant independent of n. In the pre- 

 ceding paragraph it was roughly assumed that 6 = 0.002 if n is reckoned 

 in thousands per cubic centimeter. Hence a = 0.000002 X n 2 . Thus 

 if = io 3 , a = 2 per cubic centimeter per second; if m = io 6 , a = 2 X io 6 , 

 etc. Experiments were tried with the radium tube on a pendulum 

 swinging above the fog chamber; also with the tube on an inclined plane 

 moving rapidly across the chamber. But in both cases the results, 

 which essentially require the opening of the stopcock of the fog chamber, 

 are too involved to have any critical value, and they are therefore dis- 

 carded here. 



65. Condensation phenomena of the inclosed steam jet. Methods 

 and results. Some time ago (Bulletin No. 12, U. S. Weather Bureau, 

 1893), I obtained a series of results (shown for example in fig. 52) from 

 observations of the behavior of the steam jet inclosed in a wide tube 

 of thin sheet metal. The jet shown at j in fig. 50 plays into the tube 

 AkA, about 2 inches wide and 2 or more feet long, the steam escaping 

 at B. Sky -light L, from a mirror M, enters the tube axially, through 

 a window a, and is observed through an opposite window, g. Room air 

 enters at C, to cool the steam, and the temperature of the inflowing air 

 is taken, as well as the pressure under which the steam escapes. Fig. 51 

 shows two such tubes arranged for differential work. These data are 

 used in the construction of fig. 52, where air temperatures in degrees 

 centigrade are horizontal and steam pressures in pounds vertical. 



