AND SOME ANALOGOUS RAYS. 
487 
luminesced, though less brightly, when was used to produce para-cathodic rays. 
A horse-shoe magnet, placed with its poles on either side of the neck joining the two 
horizontal tubes, deflected the rays. When the screen of aluminium foil was shaken 
into its place to intercept the rays, the luminescence of almost-all the above-mentioned 
materials was stopped. The scheelite proved to be the most luminescible of them, 
but no effect was produced upon it at any exhaustion up to the highest, unless the 
screen was itself also made cathodic by joining the lead slide in Hi through a resistance 
to the cathode pole. The luminescence of the scheelite under these conditions was 
faint, and the tint, instead of the usual bluish-green, was of a lavender colour. The 
magnet did not seem to affect the production of this luminescence. Under no circum¬ 
stances did the ruby luminesce when the aluminium screen was present. 
A narrow aperture was punctured with a penknife through one of the thicker 
screens in the lead slide, and the effect was observed of throwing ortho-cathodic and 
para-cathodic rays through this slit upon the luminescible materials below. If the 
screen was itself neutral or anodic the luminescent effects of the rav that traversed 
the screen were exactly the same in kind as those produced on the same materials 
when the screen was absent. With para-cathodic rays the effects were the same as 
those with ortho-cathodic, but fainter, and in the case of several materials, particu¬ 
larly the ruby, so faint as to be practically invisible. When, however, the perforated 
screen was made cathodic, somewhat different results followed. The cathode rav, 
which was thus filtered through a slit in a negatively electrified or cathodic screen, 
no longer produced an effect identical in kind; the luminescence was, in general, 
weaker, but the tints differed, being in general duller. 
The action of the magnet on rays filtered through a narrow hole in the diaphragm 
was carefully observed, a patch of the leaden surface of the slide, Hg, coated with 
powdered scheelite, being used as a luminescent screen to watch the effects. The 
beam of cathode rays streaming downward from Kg, and falling upon the perforated 
screen, was intercepted save the small part which passed through the aperture. 
When this small beam entered the magnetic field between the magnet-j^oles it was 
spread out, as described by Wiedemann and Ebert, •''' and by the author,! several 
patches of luminescence appearing on the scheelite surface, where it was struck by 
rays of different degrees of deflectibility. The exhaustion was varied while the 
magnet remained in place, when it appeared that the deflexion of any given ray did 
not depend on the degree of exhaustion. But as the vacuum was carried to a higher 
point the more-deflected patches of luminosity died out, while the less-deflected 
patches persisted. This is not inconsistent with the observation of Crookes,^ who 
* O-p. cit. 
t See supra. The above apparatus was made early in June, 1896, before the publication of the 
researches of M. Biekeland on the magnetic spectrum. The results were briefly described by the author 
at the British Association meeting in September, 1896. 
X ‘Phil. Trans.,’ 1879, Part I., p, 160 (‘The Bakerian Lecture,’ Aid. 577). 
