310 MM. Oumoff and Samoi'loff on Electric 



We proceed to the description of the experiments : — 



(1) No object being interposed between the tube and the 

 screen we obtain on the two faces of the latter an intensely 

 red spot corresponding to the fluorescent spot in the tube ; 

 the remainder of the plate acquires a reddish tint. The same 

 effect is obtained on the four faces of two ebonite plates placed 

 one on the other and making good contact. Thus the fluo- 

 rescent spot of the Hittorfs tube sets up a negative electrifi- 

 cation on the faces of dielectrics in its neighbourhood, whether 

 these faces are turned towards the tube or away from it. On 

 the portions of juxtaposed plates which are not in intimate 

 contact we find yellow spots and red ones opposite to each 

 other. The spot formed on the front face of the plate is 

 sharply defined ; for this reason we must conclude that the 

 action of the tube is propagated by trajectories emanating 

 from its surface. 



(2) On covering the ebonite plate by a sheet of zinc the 

 plate appears red on both sides. On putting the same sheet 

 below the plate and in contact with it the face of the plate 

 turned towards the zinc acquires a yellow hue, the opposite 

 face an indefinite tint. We may say in short, that every body 

 introduced into the field, if in perfect contact with a dielec- 

 tric, does not change the negative electrification of the latter 

 produced by the field, provided the body is between the 

 tube and the dielectric ; when the dielectric is between the 

 tube and the body, the negative action of the field is replaced 

 by a positive action. This conclusion is confirmed by the 

 following experiments : — 



(3) Figures cut out of metal (lead, zinc, aluminium), glass, 

 and paper in perfect contact with the screen give, when they 

 are placed above it, red images, and when they are beneath, 

 yellow images. The images are bordered by a neutral band ; 

 the rest of the screen is red. 



On placing a glass plate beneath the plate of ebonite on 

 which the cuttings are arranged the red ground which sur- 

 rounds the images of the objects changes to an intense yellow 

 field ; as to the images, their colour appears to tend to black. 

 Occasionally yellow tufts are seen which come from points 

 corresponding to projecting points of the objects. The rim 

 of the glass vessel which supports the ebonite plate always 

 gives a circle of an intense yellow except at the points which 

 are not in contact with the ebonite ; to these points corre- 

 spond red arcs. 



(4) A rectangle cut from a sheet of lead and having a 

 rectangular opening in the middle was placed above the plate 

 and in contact with it. The image of the metallic portion is 



