1881.1 



on the Phenomena of the Eleetric Discharge. 



4H7 



au induction coil charge up sncli a tube first witli positive, then with 

 negative, electricity, and produce an illumination in consequence of 

 the alternating charge and discharge of the walls of it. When I turn 

 on the battery current you will perceive a flash, tlien if I reverse the 

 current another flash, and if I do this quickly I make the illumi- 

 nation a little more persistent. But I have a rapidly reversed com- 

 mutator by which I can reverse the current 350 times in a second, 

 and you see that with its help I can illuminate the tube very beau- 

 tifully. 



In almost every case there is a dark interval near the negative 

 terminal, but occasionally we have met with tubes in which the strata 

 completely fill the tube, the last ones threading themselves on the wire 

 used for the negative terminal (Fig, 24). Unfortunately I have not 

 one which I can show you, as these tubes which have shown this phase 

 completely change after the current had passed a very short time. 



Fig. 24. 



TUBE 123. 



I now propose to show, with the aid of my two assistants, 

 Messrs. James Fram and Ernest Davis, some tubes with various 

 gases at difterent degrees of exhaust, in order that you may see the 

 strata in all their beauty and witness the changes of which I have 

 spoken. 



I will in the first place show a tube in which there are produced 

 a series of luminosities like those in one of the photographs which 

 were projected on the screen. It is No. 148, with residual hydrogen 

 at a pressure of 4 millimetres, and connected with 7920 cells. Fig. 8 

 in the plate shows the phenomenon ; it is from a photograph obtained 

 in four seconds. 



Tube 201, shown by Fig. 7 in the plate, is a hydrogen vacuum 

 at a pressure of 0*8 millimetre; with 3600 cells and an interposed 

 resistance of 1,500,000 ohms a perfectly steady close stratification is 

 produced. The figure is copied from a photograph obtained in three 

 seconds. 



Tube 139, shown in the plate by Fig. 4, is a hydrogen vacuum, 

 pressure • 8 millimetre, with 3600 cells and an interposed resistance 

 of 200,000 ohms. A series of beautiful blue double strata are pro- 

 duced, with a carmine line between the double strata. The figure is 

 copied from a photograph obtained in one and a half second. 



Tube 139. — On interposing 500,000 ohms resistance in the circuit, 



