532 
Proceedings of Royal Society of Edinburgh. [sess. 
While we notice a displacement of the centres of the lines 
towards the red in the first period, we also see clearly their shiit 
towards the violet in the second period, therefore confirming the 
conclusions drawn from figs. 6 and 7. Now, Professor Campbell 
of the Lick Observatory has given special attention to this shift 
of the bands during the second period, and has found evidence 
of a tendency of these bands to approach their normal positions. 
His measurements were made on the chief nebular line X= 5007*15 
(normal). They are exhibited in the following table taken from 
p. 293 of Scheiner-Frost’s Astronomical Spectroscopy. 
1892. Aug. 
20-30. X 
= 5003*3 
AX = - 3*8 t.m. 
Sept. 
3-22. 
5002*2 
-4*9 
Oct. 
12-19. 
5003*7 
-3*4 
Nov. 
2-24. 
5004*6 
-2*5 
1893. Feb. 
10-27. 
5006*0 
-1*1 
Mar. 
26-May 9. 
5005*3 
-1*8 
Aug. 
6-Oct. 10. 
5005*9 
- 1*2 
The decrease in AX is quite apparent. In 1892 the displacement 
amounted to about - 4 t.m., a value which agrees very well with 
that of the H-lines of the preceding table. In 1893, on the other 
hand, the displacement was only about - 1*5 t.m. Since we had 
found before from other considerations that this was probably in 
amount and sign the common displacement of the whole system, 
we conclude that at this stage the intensity-curve of the hands 
must have approximately agreed with that given in fig. 8. 
Thus the theory here discussed seems to offer a simple and 
probable explanation of an otherwise extremely puzzling pheno- 
menon, viz., of the enormous shift of the bands from red towards 
violet during the time between the first and second period of the 
history of Nova Aurigae. 
So far, our attempt to explain the character of the spectrum of 
Novae on the basis of Seeliger’s theory has been of a purely 
qualitative character. It is important to show now its possibility 
also from the quantitative point of view. In order to explain the 
displacements of the absorption-bands towards the violet by 
motions in the line of sight, we have to assume average velocities 
of the expanding gases amounting to about 600 km. per second. 
