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RETROGRADE RA YS 79

collision the portion which is without charge, and
which have not made a collision the negatively electrified

portion of these rays.

These retrograde rays are very well developed when a
double cathode of the kind Introduced by Goldstein (see p. 5)
Is used instead of a flat cathode. If a cathode consisting of
two parallel triangular plates. Fig. 41, is substituted for the
flat cathode B in the apparatus, shown in Fig. 40, a plentiful
supply of retrograde rays come from the cathode when it is
turned into a suitable position. By twisting the triangle round
by means of the glass stopper the emission of the rays, both

SWWB^p

^-*~ /»

FIG. 41.

cathodic and retrograde, could be determined. In this way it
was shown that the maximum emission of cathodic rays is
along the line starting from the middle points of the sides.
At the higher pressures this is practically the only direction
in which cathode rays can be detected; at very low pressures,
however, cathode rays can be detected coming from the corners
of the triangle as well as from the middle points of the sides.
Few, if any, however, are given out in any intermediate direc-
tion. The positively electrified particles stream off at all
pressures from both the corners and middle points of the sides,
but not from the intermediate positions. The most abundant
stream comes, as for the cathode rays, from the middle points of



	*RETROGRADE* RA YS 79 collision the portion which is without charge, and which have not made a collision the negatively electrified portion of these rays. These retrograde rays are very well developed when a double cathode of the kind Introduced by Goldstein (see p. 5) Is used instead of a flat cathode. If a cathode consisting of two parallel triangular plates. Fig. 41, is substituted for the flat cathode B in the apparatus, shown in Fig. 40, a plentiful supply of retrograde rays come from the cathode when it is turned into a suitable position. By twisting the triangle round by means of the glass stopper the emission of the rays, both

	A: SWWB^p	^-*~ /»

	FIG. 41.

	cathodic and retrograde, could be determined. In this way it was shown that the maximum emission of cathodic rays is along the line starting from the middle points of the sides. At the higher pressures this is practically the only direction in which cathode rays can be detected; at very low pressures, however, cathode rays can be detected coming from the corners of the triangle as well as from the middle points of the sides. Few, if any, however, are given out in any intermediate direc- tion. The positively electrified particles stream off at all pressures from both the corners and middle points of the sides, but not from the intermediate positions. The most abundant stream comes, as for the cathode rays, from the middle points of