310 Mr Willows, On the distance between the striae in the positive 



Fig. 2 shows at a glance the relation between current and 

 distance apart of the striae in a tube 12 mm. in diameter when 

 filled with hydrogen. The abscissae are galvanometer deflexions, 

 the ordinates distance between successive striae. 



Fig. 



2. Curves showing the relation between current and distance apart of the 

 striae in hydrogen. 



The figures on the curves denote the constant pressure at which 

 the measurements were taken. 



When the discharge was passing in a tube an increase of 

 resistance in the liquid rheostat caused the current to decrease 

 at first, without much alteration of the potential difference at 

 the terminals, but finally a point was reached at which a large 

 increase in resistance caused no further decrease in current ; this 

 was the minimum current required to carry the discharge. At 

 this stage the striae were steadier than under any other con- 

 ditions, and a telephone in the circuit was nearly or quite silent. 

 Starting from this point, an increase in current causes a rapid 

 increase in distance between the striae, the rate of increase gets 

 less as the current gets bigger until a maximum distance is 

 reached, after which a further increase in current causes them 

 to approach each other. 



The rate at which the striae separate or approach is different 

 for different pressures as is shown by the cutting of curves A and B. 

 Curve G is referred to later. 



As the pressure is diminished the value of the maximum 



