the <; anal-Ray Group 
379 
rectangles not only at the places in contact with the first 
layer, but those rays which pass in a grazing direction over 
the walls enter the slit along the directions which the rays 
of the first layer have at the corresponding portions of the 
edge. Now there appears to apply to the Sprays of a plane 
cathode a law entirely analogous to that which has long ago* 
been established in connexion with the ordinary cathode rays 
easily deflected by a magnet — viz.. that if the pressure be 
maintained constant, the rays are the more strongly inclined 
towards the axis of the plate the nearer the starting-point of 
the rays is to the edge of the plate, and that the less the 
pressure the more does this inclination of the rays increase. 
This not only explains why with decreasing pressure the 
boundaries of the band arising from a slit converge more 
and more (corresponding to the increasing divergence of the 
S L -rays), but also accounts for the fact that the luminous 
bands of a system of parallel slits in a plane plate converge 
towards each other and towards the axis of the plate. 
In the case of cathodes which either entirely or nearly fill 
the opening of the tube, we also have to consider, when 
working at low pressures, the recently investigated f obliquity 
of the boundaries of the first layer due, on the one hand, to 
the repellent anodic action exerted on its base at the cathode, 
and, on the other, to an attraction of the rays by a cathodic 
zone of the wall which lies in the neigh- 
bourhood of the outer limit of Crookes's 
space. If under this influence the ex- 
treme Sprays assume the form shown 
in fig. 8, there results a canal-ray band 
with very strongly convergent boun- 
daries (shown dotted in fig. 8). 
In this connexion it may not be out 
of place to refer briefly to the effect of 
very weak magnets on the canal rays. 
In the case represented in fig. 8, it is 
possible, by means of a weak and small 
horseshoe magnet held horizontally — the 
slit having an equatorial direction — to 
produce great changes in the directions 
of the boundaries of the luminous band, 
and to render one or other of the boun- 
daries verv much more oblique. 
Fig. 8. 
* E. Goldstein, Sitzungsber. d. k. Akad. d. Wissensch. zu Berlin, 1881 
p. 799; Wied. Ann. xv. p. 274 (1882). 
t E. Goldstein, Verltandl. d. Deutsch. Physih. Gesellsch.iv.ip.64: (1902). 
+ 
