SPECTRUM ANALYSIS OF THE HEAVENLY BODIES. 157 
It must not be forgotten that the whole of the proper motion which can 
be directly observed by us, consists of that portion only which is at right 
angles to the visual ray. This motion, according to the parallax we attri- 
bute to Sirius (Henderson=0""150, Abbe=0'27), will vary from 24 miles 
to 43 miles per second. 
The real motion of the star will consist of this motion, combined with the 
motion at right angles to it, obtained by the present investigation, of 29 miles 
from the earth. 
Similar observations have been made of several other stars; I desire, how- 
eyer, to submit them to a re-examination. 
B. Other Spectroscopic Observations of the Fived Stars. 
a Herculis—On several occasions the spectrum of this star was re-ex- 
amined. The observations agree with the measures and comparisons of 
the chemical elements of this star obtained in 1863. The spectrum is con- 
tinuous, with numerous groups of dark lines. 
Mira Ceti gives a spectrum apparently identical, or nearly so, with a 
Orionis. At the time the star was waning in brightness there was an appear- 
ance of greater intensity in several of the groups, but further observations 
are required before any opinion is hazarded as to the cause of its remarkable 
periodical variation in brightness. 
y Cassiopeiw.—In addition to the bright line near the boundary of the 
green and blue observed by Father Secchi, I discovered a line of equal bril- 
liancy in the red. ‘There are also in the spectrum of this star dark lines due 
to absorption. The two bright lines are narrow and defined, but are not 
yery brilliant. Micrometrical measures of these bright lines show that they 
are doubtless coincident in position in the spectrum with Fraunhofer’s C and 
F, and with two of the bright lines of luminous hydrogen. 
I have confirmed the interesting observations of MM. Wolf and Rayet, so 
far as to the presence of bright lines in the three small stars described by 
them. I haye not determined the number and positions of these lines. 
§ I. Oxservartons or roe Nesune. 
My observations on these bodies have confirmed the results of my former 
investigation, but have not afforded much information which is new. Out 
of about seventy nebulw, nearly one-third gave a spectrum of bright lines. 
The differences which have been observed between the spectra of the 
objects which give bright lines, may be regarded as modifications only of the 
typical form of spectrum represented in fig. 2. Pl. Y. 
The variations consist of differences of relative intensity, and, in some 
cases, of the absence of one or two of the lines. It is worthy of remark 
that, so far as the nebula have been observed, the brightest of the three 
lines, which is coincident with a line of nitrogen, is always present, and 
sometimes the spectrum consists wholly of this line. It is a suggestive fact 
that in no nebula haye any additional lines been observed on the less refran- 
gible and brighter side of the line common to all the nebulx. In two or 
three nebule a fourth line, more refrangible than those represented in the 
diagram, has been detected. 
The spectrum of the Great Nebula in Orion was observed and compared 
with terrestrial lines, in the powerful spectroscope described in this paper. 
The coincidence of the strongest line with a double line of nitrogen, though 
now subjected to a much more severe trial (to a spreading out of the spec- 
trum nearly three times greater than in my former observations), appeared 
as perfect as before, 
