When the bulb hangs with the globe L down, the rotation is always clockwise.  In the southern hemisphere it would occur in the opposite direction and on the equator the brush should not turn at all.  The rotation may be reversed by a magnet kept at some distance.  The brush rotates best, seemingly, when it is at right angles to the lines of force of the earth.  It very likely rotates, when at its maximum speed, in synchronism with the alternations, say 10,000 times a second.  The rotation can be slowed down or accelerated by the approach or receding of the observer, or any conducting body, but it cannot be reversed by putting the bulb in any position.  When it is in the state of the highest sensitiveness and the potential or frequency be varied the sensitiveness is rapidly diminished.  Changing either of these but little will generally stop the rotation.  The sensitiveness is likewise affected by the variations of temperature.  To attain great sensitiveness it is necessary to have the small sphere s in the centre of the globe L, as otherwise the electrostatic action of the glass of the globe will tend to stop the rotation.  The sphere s should be small and of uniform thickness; any dissymmetry of course has the effect to diminish the sensitiveness.

The fact that the brush rotates in a definite direction in a permanent magnetic field seems to show that in alternating currents of very high frequency the positive and negative impulses are not equal, but that one always preponderates over the other.

Of course, this rotation in one direction may be due to the action of two elements of the same current upon each other, or to the action of the field produced by one of the elements upon the other, as in a series motor, without necessarily one impulse being stronger than the other.  The fact that the brush turns, as far as I could observe, in any position, would speak for this view.  In such case it would turn at any point of the earth’s surface.  But, on the other hand, it is then hard to explain why a permanent magnet should reverse the rotation, and one must assume the preponderance of impulses of one kind.

As to the causes of the formation of the brush or stream, I think it is due to the electrostatic action of the globe and the dissymmetry of the parts.  If the small bulb s and the globe L were perfect concentric spheres, and the glass throughout of the same thickness and quality, I think the brush would not form, as the tendency to pass would be equal on all sides.  That the formation of the stream is due to an irregularity is apparent from the fact that it has the tendency to remain in one position, and rotation occurs most generally only when it is brought out of this position by electrostatic or magnetic influence.  When in an extremely sensitive state it rests in one position, most curious experiments may be performed with it.  For instance, the experimenter may, by selecting a proper position, approach the hand at a certain considerable