DOPPLER EFFECT 155

lines was, however, very small compared with that of the
undisplaced lines, while in the spark lines the displaced
intensity1 is quite comparable with the normal intensity.

Nitrogen has a line spectrum which has not been resolved
into series, and some banded spectra. The line spectrum and one
of the banded spectra are found where nitrogen positive rays
go through nitrogen ; the banded spectrum does not show the
Doppler effect. Some of the lines in the line spectrum show
it very distinctly, while it is quite absent from others (Her-
man, Wilsar). A very interesting point about the effect in
nitrogen is that even for those lines which show the effect the
value of AHl is not constant Wilsar3 gives the following
table for the Doppler effect for some of the nitrogen lines:—

Wave Length.
AA/A.

5002*9
II'4

4643-4
10-35

4630-9
10-14

4S30"3
10*60

3995'2
6-90

Thus the effect for the line 3995'2 is much less than for
any of the others, showing that the velocity of the source of
this line is considerably less than that of the sources of the
others. The different states in which nitrogen occurs in the
positive rays are atoms with two charges, atoms with one
charge, molecules with one charge, and in exceptional cases
atoms with three charges and a tri-atomic molecule with one
charge. If the majority of the lines were given out by the
doubly charged atom, and the line 3995"2 by the singly charged
one, we should get relative values of Alfl, approximately
equal to those in the preceding table.

1 Paschen, u Ann. tier Phys./J 23, p» 261, 1907,
.' 8 "Phys. Zeit," 7, p. 568, 1906,' with the series