each other; in other words, it is polarized in the complete sense of the term.
The phenomenon is easy to observe when the spark is well regulated; this means that the spark must be very small and faint.
If the focus tube is made to turn about its axis, which is parallel to the cathode rays, the observed phenomena do not change, so long as "X" rays reach the gap. The plane of action is thus independent of the orientation of the anticathode, being always the plane passing through the "X" rays and the generating cathodic rays.
The spark being kept in this plane, and turned round from the position in which it is at right angles to the "X" rays to that in which it is parallel to them, we observe that the effect of the "X" rays on the brightness of the spark is a maximum in the first position, and diminishes to nothing in the second.
Now, an "X" ray and its generating cathodic ray only determine a plane when their directions are different. Again, amongst the emitted "X" rays, some are in a direction very nearly the same as that of the cathode rays, being