Many interesting experiments with these rays may be performed with tubes permanently exhausted to the proper degree. The power of the rays to produce phosphorescence is shown in a most striking way with a tube fixed in a horizontal position upon a stand, and containing a light cross made of aluminium, placed in the path of the rays. This is hinged at the base, so that it can be stood up on end or thrown down by jerking the tube. Some of the rays streaming from the cathode are intercepted by the cross, while others pass by it and reach the other end of the tube. The result is that a black shadow of the cross is thrown on the glass, sharply contrasted with those parts of the tube reached by the rays, and which phosphoresce brilliantly. After a little while this brilliance decreases, for the glass becomes fatigued, and loses to a considerable extent its power of phosphorescing. If now the cross is jerked down, the rays reach the portions of the tube before protected by the cross, and this glass, being quite fresh, phosphoresces with full brilliance. The black cross now suddenly becomes brilliantly illuminated, while the tired glass is dark in comparison. If the tired glass is allowed to rest for a while it partly recovers its phosphorescing powers, but it never regains its first brilliance. An even more striking experiment may be made with a horizontal tube containing a tiny wheel with vanes of mica, something like a miniature water-wheel, mounted on glass rails. When the discharges are sent through the tube, the cathode rays strike against the vanes and cause the little wheel to move forward in the direction of the anode. Other experiments show that the cathode rays have great heating power, and that they are deflected by a magnet held close to the tube.