A Singular Behaviour of Striæ in the Positive Column of an Electrical Discharge through Hydrogen

Abstract

THE following behaviour of some striæ in the positive column of an electrical discharge through rarefied hydrogen seems to be of sufficient interest to warrant a description. The distances between adjacent striæ in hydrogen change with gas pressure in an anomalous manner first noted by Willows (Proc. Camb. Phil. Soc., 10, 302; 1900), in that, with reduction of pressure, they at first increase in magnitude, pass through a maximum value and then in turn through a minimum value. This minimum occurred at about 1.5 mm. pressure in the discharge tubes I used, which had an internal diameter of 11 mm. The striæ here were bluish in colour, whereas at the other pressures their colour was reddish. The phenomenon to be described was only observed in this narrow pressure region where the striæ were most closely packed. The discharge current was kept constant at 6 milliamperes and it passed between cold electrodes consisting of aluminium cylinders 2 mm. in diameter.