Emanations of Pli.osphorus through Air and other Media. 399 



Table IV. 



Value of K = AJJn e log e/C ; c' = K/,ve a * /A ; 

 -(dV/dt) log e/V = d. 



Plates. 



Distance 

 apart, x. 



Observed 

 leakage per 

 minute, c'. 



Computed 

 c'. 



K. 



A = 132cm. 2 

 a = 46 cm. 



a/ A — -35 



cm. 

 17 



1-8 



2-5 



37 



57 



115 



•200 

 •162 

 •128 

 •044 

 •024 

 •002 



•200 

 •182 

 •101 

 •044 

 •013 

 •001 



•634 



The curve so computed is shown on the chart (fig. 5), and 

 the observations are inserted with reference to it. It will be 

 seen that the coincidence is surprisingly good, lending to the 

 new equation deduced a degree of probability, which becomes 

 enhanced when viewed in connexion with the similar result 

 of my last paper. 



10. It is even possible to make an approach tow r ard com- 

 puting the constant n . If, conformably with c ; , the value of 

 K be taken relatively to minutes instead of seconds, the 

 equation becomes K=26AU?* <?/^- Now if the velocity of 

 the ions produced by phosphorus is like that of the other 

 gases, U is of the order (say) of 1 centim. per second 

 (Thomson, Rutherford, Townsend, Chattock), and e of the 

 order of 7/10 -10 electrostatic units or 2*4 X 10 -19 coulombs. 

 (Thomson). The ratio of areas in my condenser was *35, 

 the area A = 132 cm.", the capacity 0, estimated at 60 centims. 

 or "7 x 10~ 10 farads. Finally, the value of K found in the 

 last table is K = *634. Thus the initial saturation, or the 

 number of ions 



?? = -634 x -7 x 10" 10 /26 x 132 x 1 x 2-4 x 10" ]0 =5-5 x 10 4 . 



Hence if all the ions which reach and are absorbed by the 

 condenser-plates actually convey charge, less than 10 5 and 

 more than 10 4 ions per cubic centim. occur in the saturated 

 emanation* contiguous to the surface of the phosphorus grid. 



* If the emanation of phosphorus is ionized air, U = lo, and » = 3*6 

 Xl0 l , agreeing very well with J. J. Thomson's 4xlO l ; cf. Phil. Mag* 

 [5] xlvi. p. 541 (1898). 



