394 



Prof. C. Barus on the Transmission of the 



for the present either the meaning of —{dVjdt)jY or 

 — (dQ/dt)/Q, where Q is the charge of the one condenser- 

 plate, the other being kept at zero. The justification of this 

 equation is at hand. Let n be the number o£ ions available, 

 e the average charge of each, U their relative velocity, x 

 the distance apart of the condenser-plates of area A for the 

 potential-difference Y. Then 



- (dQ/dt) = U( V/x) kne = - C {dV/dt) , 



where C is the capacity of the condensers conjointly, (dQ/dt) 

 being the current. It will be convenient to express the 

 data in terms of common logarithms, wherefore 



c'= -log e(dV/dt)/Y will be given, and V = V 10~ c ^ 



4. The first question at issue is the behaviour of phosphorus 

 itself, the object, being to throw light on its persistence as an 

 ionizing agent in the lapse of time (ageing), change of tem- 

 perature, &c. The following tables show results. The leakage 

 of the condenser was observed in the lapse of time, the apparatus 

 being charged at successive intervals, but not otherwise 

 interfered with. The constant c (varying with n the number 

 of ions per cubic centim.) was found for each two minutes 

 after charging. Plate- distances of 1 and 3 centims. occur. 

 The data are summarized for the three series of results in 

 hand. The limit of sensitiveness of the electrometer was 

 about equivalent to S<r'='002. The largest values of c' 

 observed were of the order of '500. 



Table I. — Persistence of the Ionizing Activity of Phosphorus, 

 in lapse of time. 



c / m 10=_(dV/V)/V. 



Dis- 

 tance. 



X. 



Mean 

 Time of 



obs. 



c'xlC 3 . 



Dis- 

 tance. 



x. 



Time of 

 action. 



c' X TO 3 . 



Dis- 

 tance. 



X. 



Mean 



Tune of 

 obs. 



c'xlO 3 . 



cm. 

 1 



10 20 



390 



cm. 

 3 



h m 

 11 39 



95 



cm. 

 3 



h m 

 2 45 



81 





26 



390 





58 



83 





56 



78 





37 



370 





12 15 



66 





3 17 



86 





47 



340 





33 



96 





48 



78 





60 



350 





40 



80 





18 



78 





11 28 



340 





57 



93 





46 



70 





12 1 



330 











5 23 



80 



