284 PROFESSOR L. BECKER ON 
TaBLE XVI. 
da, 
A 
” (s] Eee eas 
Nebule. 
3869°5 +0:1 
3968°0 0:0 
4103°4 +0°3 4101°8 + 2:1 
4341:0 +0°3 4340°7 + 0-6 
4364°5 +0°3 
4612°6 +0°4 
4642°0 +0-4 
or (4635°3) | +04 (4633'8) 
4687°8 +0°4 
4715-6 +04 
4726°1 +04 
4862°8 +04 4861°5 +1°6 
4959-4 +0-4 4959°0 +07 
5007°2 +0°4 5007-0 +0°6 
The five lines mentioned above give on an average da,,= +11 t.m. Aj calculated by 
the third formula is comparable with the wave-lengths of elements, and also with the 
A, derived from the March-April plates (Table VII.). The motion of the new star in the 
line of sight is here eliminated. If one should succeed in deriving from experiments, 
or theoretical considerations, the wave-length »’ of a certain point a) of the band belong- 
ing to a line ’,, a’ can be calculated from a’ = (X’ —A,)4500/X’, and the ratio (a) — a’)/4500 
is the ratio of the velocity in the line of sight and the velocity of light. 
The residuals entered in the column headed “ Difference” of Table XVII. exceed the 
quantity that might be expected from the average error of X,,, and perhaps the fact that 
they rest on fewer minima than those of the brighter bands made them less accurate 
than the latter. Some of the bands call for special remarks. The zero of the second 
band lies 1°6 t.m. from the calcium line 3968°6, and 3°2 t.m. from the hydrogen 
line 3970°2._ Owing to the good definition of its minima and its isolated position, its 
wave-length is one of the best determined of the spectrum, and its error is not likely to 
be greater than the calculated average error. As da, cannot be so much in error, | 
take the band to belong neither to calcium nor to hydrogen. The bright band whose 
zero has the wave-length 4641°3 cannot be identified. This band overlaps the band, 
A, = 4611°9, and only two of the three minima were measured. The zero would almost 
agree with the bright hydrogen line 4633°8 if the observed minima were not the first and 
second of the standard band, but the second and third ; an assumption which changes the 
wave-length of the zero by the distance of two minima. This identification is bracketed 
as an alternative, though it is questionable, because the first calculated maximum of the 
band has not been observed (see Table XII.). The next band, \, = 46871, is certainly 
