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THE PHOTOGRAPHS

duced by the particles which have been charged during the
whole of their journey. If the junction occurs at a consider-
able distance from the head of the primary, care has to be

taken in some cases to avoid confusing the secondaries with
primaries corresponding to a different value of ejm. Thus, for
example, if the shape of the secondary and primary were

FIG. 23.

similar to that shown in Fig. 23*2, and the point of junction
came off the plate, the appearance on the plate would be that
represented in Fig. 23$, and the secondary might be mistaken
for a primary with a value of e\m less than the true value. If
the magnetic field overlapped the electric field on the camera

FIG. 24.

side of the apparatus, the primary and secondary would re-
semble Fig. 23^, and if the right hand part were off the plate,
the curves would look like Fig. 246 and the secondary might be
mistaken for a primary with a value of e/m greater than the
true value. This possible confusion of a secondary with a
primary line is a point which requires careful attention when



	THE PHOTOGRAPHS	33

	duced by the particles which have been charged during the whole of their journey. If the junction occurs at a consider- able distance from the head of the primary, care has to be taken in some cases to avoid confusing the secondaries with primaries corresponding to a different value of ejm. Thus, for example, if the shape of the secondary and primary were



	FIG. 23. similar to that shown in Fig. 232, and the point of junction came off the plate, the appearance on the plate would be that represented in Fig. 23$, and the secondary might be mistaken for a primary with a value of e\m* less than the true value. If the magnetic field overlapped the electric field on the camera



	FIG. 24. side of the apparatus, the primary and secondary would re- semble Fig. 23^, and if the right hand part were off the plate, the curves would look like Fig. 246 and the secondary might be mistaken for a primary with a value of e/m greater than the true value. This possible confusion of a secondary with a primary line is a point which requires careful attention when 3