620 
MESSRS. W. SPOTTISWOODE AND J. FLETCHER MOULTON 
tube. It left, of course, an opening along its length, and when it was connected to 
earth this became phosphorescent from the relief-phosphorescence. The directions of 
the streams producing this phosphorescence were substantially the same as those to 
which we have seen reason to believe the attendant phosphorescence is due. An 
electro-magnet was tried upon this strip of phosphorescence, and it produced similar 
results to those above described, thus strongly confirming the truth of the theory we 
have adopted to account for the genesis of the attendant phosphorescence. 
One more peculiarity remains to be noticed with regard to this attendant phos¬ 
phorescence. It is possible, as we have said, to cause it to separate slightly from the 
positive luminosity with which, as we have said, it is so closely bound up. One way 
is by bringing the positive luminosity across some piece of wire or other conductor in 
the tube; but as this phenomenon is obscure and difficult to observe we shall not 
dwell on it further. The other way is by approaching a conductor to the tube on one 
side or the other of the position which surrounding circumstances have constrained the 
positive luminosity to take up. It is often possible by doing this to drive the green 
phosphorescence a little distance off on the further side of the positive luminosity to 
that on which the conductor is. It would seem as though the phosphorescence were 
more strongly repelled than even the positive luminosity. A straight wire in con¬ 
nexion with earth was placed at an angle to the axis of the tube, and made to 
approach it. The green line assumed a serpentine form, cutting the positive lumi¬ 
nosity at its point of inflexion (Plate 29, fig. 28). The solution doubtless is connected 
witli the fact that the presence of the conductor renders negative discharge easier from 
the part of the tube nearest to it, and that the streams of molecules, in consequence of 
their inertia, persist hr maintaining a nearly diametral path although the direction 
from which comes the demand for the negative discharge which is inclined at an angle 
to this.'" 
We will now return to the excepted case in which the positive luminosity is made 
to pass in a zigzag direction through the tube (Plate 29, fig. 27). As we have said, 
the places where it appears to impinge on the side of the tube are marked by patches 
of phosphorescence. These patches are as a rule exceptionally brilliant. If an object 
within the tube be situated so that the column of luminosity comes into contact with 
it on thus crossing the tube, it will be found that it casts a shadow in the direction in 
which the column strikes it—that is to say, in the direction of the course of the 
column as we proceed towards the positive terminal. In fact, in such cases the 
shadow is much as it would be if the column were threaded throughout its whole 
length by molecular streams coming from the negative terminal and proceeding 
towards the positive terminal. 
Now before we proceed further we must call attention to the fact that it is only 
* If the conductor be brought towards the other side of the tube exactly opposite to where the 
luminosity and its attendant phosphorescence is situated it often splits the line of phosphorescence into 
two, one situated on each side of the thin column of positive luminosity. 
