TROWBRIDGE. — DISCHARGES OF ELECTRICITY. 461 



At a still higher state of rarefaction a stria issues from the orifice in 

 the anode, and this also shelters itself behind the diaphragm on the 

 side toward the anode. There are, thus, three definite stages of strati- 

 fication in this form of tube. At a pressure of four centimetres fine 

 striae appear on the side of the orifice in the diaphragm opposite to the 

 anode. These soon disappear with increasing rarefaction. At a pres- 

 sure of approximately 3 mm. a large stria shelters itself behind the 

 diaphragm. This fades into the orifice in the anode with diminishing 

 pressure; and at a pressure of approximately .15 mm. a large stria 

 wells up out of the orifice in the anode and takes a similiar place near 

 the diaphragm. When the state of canalstrahlen is reached, all striae 

 have been driven into the anode. Can we regard these strahlen as a 

 stratification which cannot be driven back by the cathode rays 1 In this 

 form of tube we find evidence of successive states of stratification which 

 may depend upon positive rays of different velocity. 



When we turn from our observation of stratification in the neighbor- 

 hood of the cathode instead of in the neighborhood of the anode, we 

 find that a stratification always takes place on the glass wall close to 

 the entrance of the cathode, or to its sealing in place. It can be pro- 

 duced equally well by causing the cathode to approach the wall of 

 the tube opposite to this sealing in place. Figure 8 represents the 

 phenomenon in a tube with a dome-shaped chamber near the electrode. 

 We seem to have two dissected striae : one on the wall of the tube 

 nearest to the cathode, which provides a beautiful light blue cathode 

 beam thrown into the dome ; and another stria on the opposite wall of 

 the dome. The original cathode beam excites both positive and nega- 

 tive rays in these striae. In considering these detached striae it seems 

 that the cathode rays in striking the glass walls can excite both posi- 

 tive and cathode rays. 



When a spark gap is inserted in a circuit containing a discharge 

 tube which is properly exhausted to the striae stage, the latter appar- 

 ently disappear — the light of the tube becomes more brilliant and 

 fluorescence is generally manifested. This is also the case when a con- 

 denser is discharged through the tube. The eye cannot perceive any 

 evidence of stratifications ; for the brightness of the pilot spark, to- 

 gether with the fluorescence both of the gas and of the glass walls effect- 

 ually shield any striae of lesser radiance which might be present. It 

 is not possible to employ a revolving mirror. The only method which 

 seemed to promise any results in detection of possible stratifications 

 was the employment of a portrait lens of large aperture — four inches 

 — in photographing single discharges. Accordingly a discharge tube 

 was filled with hydrogen and exhausted to the striae stage. A con- 



