EXPERIMENTS WITH IONIZED AIR. 



63 



The experiments with the train of apparatus described usually progressed 

 smoothly. The data are given in table 1, wliieh is divided into three parts, refer- 

 ring respectively to the steam jet, the gasometer (volume conveyed per minute, 

 F, being the essential datum), and the electrometer. It was thought superfluous 

 to reduce the air volumes to normal conditions as the fluctuations of pressure (pres- 

 sure excess, ^>) and temperature {6} are I'elatively insignificant in view of the vari- 

 ability of the ionizei'. Vov the steam jet, the [)ressure, ^;, and teraperatui'e, 0, are 

 also practically constant (See Chai)ter II). Relatively to the electrometer series, the 

 two initial potential differences, E, are given as obtained immediately after, and 15 

 seconds after charging. These are needed in the reductions. The potential in 

 these e.xperiments usually begins with about 40 volts. The table also contains the 

 value of jE/£J', for observations half a minute apart, two of these being available 

 for each color as speciHed. The curi'ent was computed as follows : For a very 

 short time after charging the fall of potential is ajipieciably logarithmic. Hence, 

 E/ E' = lO"-*"-''' may be assumed, where ^and E' are the potential differences at 

 the times t and /', in minutes, and x a constant for a given color in the tulie. 

 Hence — G{dE/dt) = CEx .In 10 = i, if O is the aggregate capacity of the electrom- 

 eter and the condenser, and / the current flowing radially thi'ough it. Since log 

 {E/E') = —x(t-t'), or —X = dlogE/sf, the table furnishes these data with E, to 

 compute i relatively, and it was thought superfluous to supply the factor (Cln 10)/60, 

 sharply. Its estimated value is about 230/60, as the combined capacity of the elec- 

 trometer (60 cm.)and the condenser (39 cm.) is about 99 cm., roughly. This would 

 make 6'= 1.1/10'" farads and the factor (6'ln 10)/60 = 4.2/10'-. The table shows 

 a few of the values of i, in amperes. 



TABLE I.— COINCIDENT REGISTRY OF THE GASOMETER, ELECTROMETER, AND 



COLOR TUBE. 



' Yellow marked Yl' is of the ist order, the other, YI, of the second. 



