1881.J 



On Stratified Discharges. 



389 



degrees a third, a fourth, and even more images were brought out on 

 the side of the tube. In one tube of very high exhaustion, for 

 which we are indebted to Mr. Crookes, as many as eight images 

 became visible. 



The phenomena here described having been once clearly seen in 

 tubes of high exhaustion, with conical terminals, and under the in- 

 fluence of a very powerful magnet, were afterwards distinguished in 

 other tubes of less exhaustion, with other forms of terminal, and in a 

 less powerful magnetic field. 



In the absence of a magnet, the lines of radiation are approxi- 

 mately (though not exactly) normal to the surface of the negative 

 terminal for all the images ; and in a magnetic field their tendency is 

 to follow the lines of magnetic force which pass through the point of 

 issue from that surface. The effect of the magnet, therefore, whether 

 the positive or the negative terminal of the tube is presented to the 

 pole, is to direct the lines of radiation more nearly along these lines 

 of force than they would be without its action ; and since lines of 

 weaker radiation would be more affected than lines of stronger 

 radiation it follows that different images, formed by lines of 

 different strength (or velocity of discharge) would be separated from 

 one another by the magnet. A similar result would follow if they 

 differed in other respects in their normal condition. 



We have then, as an experimental fact, a series of images, each 

 formed by a system of rays issuing from the surface of the negative 

 terminal. The images being distinct, the system of rays must be 

 distinct also. Now, as it seems hardly possible to imagine that, 

 from every point of a surface, there can issue at one and the same 

 instant of time a variety of systems of radiations, each system rang- 

 ing over a finite angular distance, and each differently directed m 

 space, we are driven to the conclusion that these radiations must have 

 issued successively and not simultaneously from the terminal. In 

 other words, the various images are formed in succession. Now, the 

 entire series of images are present whenever a discharge passes 

 through the tube ; and when a " continuous " discharge (such as that 

 from a Holtz machine) is passing, they are all as steady and as per- 

 sistent as are any other features of the discharge. From this it 

 follows that the radiations are not a continuous phenomenon, but that 

 they are composed of a recurrent series of discharges, each having its 

 own angular range, and its own direction in space ; and as the elec- 

 tricity, which is the motive power, and the metallic terminal, which is 

 the directing machinery, are the same in kind for each image, we are 

 led to the conclusion that the positions of the images are determined 

 by the force with which the radiations are projected. In fact, we 

 understand that the various images are due to a succession of dis- 

 crete discharges of successively diminishing strength. 



