244 A. W. Wright — Cathode Bays and their Effects. 



or closing of the primary circuit will be rapidly extinguished, 

 and the mode of discharge will approximate closely to a simple 

 discharge at each movement of the interrupter, producing at 

 the terminal of the electrode within the tube an unsym metrical 

 rise and fall of the electrostatic potential. This must give rise 

 to the passage of inductive actions through the space surround- 

 ing the electrode both within and without the tube. The 

 period or duration and phase of these inductive pulses will be 

 essentially the same as those of the variations of potential at 

 the surface of the electrode, and as these are not a continuous 

 sequence like the elements of a train of waves, the inductive 

 actions in space may be regarded as very probably occurring in 

 the form of isolated or unsystematic pulses, succeeding one 

 another at intervals long compared with their own duration, 

 and more or less irregular with most forms of interrupters 

 used with the coil, from the variations in their action. As to 

 the mode of propagation of these pulses the most natural view 

 would be to regard them as analogous to longitudinal compres- 

 sion waves in an elastic medium, but of an unsystematic 

 character. 



It may be of interest to recall the fact that appearances 

 similar to these pictures produced by the rays from the cathode 

 of a vacuum-tube, and not unlikely due to a similar cause, have 

 been observed before. In a paper published by the writer in 

 1870,* it was shown that, under certain conditions, when the 

 silent discharge took place between the terminals of a static elec- 

 trical machine, a minute point-like brush appeared upon the 

 negative terminal, and a glow upon the positive, in which 

 appeared the figures of objects brought into the path of the 

 discharge. When a piece of wire gauze was interposed, "the 

 shadows were formed with striking distinctness. . . . Every 

 peculiarity of texture was faithfully represented, the irregu- 

 larities in the wires, breaks in the gauze, and the like, being 

 accurately reproduced, and moving with the gauze, just as in 

 the case of true optical shadows." In a subsequent paperf 

 attention was called to the fact, that many cases of images 

 formed upon the bodies of persons killed by lightning, which 

 had been reported by reputable observers, might be explained 

 by supposing that the objects represented were so situated 

 as to interrupt the lines of electrical action. These facts sug- 

 gest the probability that every electrical discharge, which is 

 not simply a flow of potential along a conductor, may produce 

 effects of a similar kind, though much inferior in accuracy of 

 form and dimensions to those produced by the agency of the 

 cathode rays from a high vacuum-tube. 



Sloane Physical Laboratory, Yale University, 

 February 22, 1896. . 



*This Journal, II, vol. xlix, May, 1870, p. 381. 



f Ibid., Ill, vol. i, June, 1871, p. 437. Also vol. x, Oet. 1875, p. 317. 



