Sherman—Study upon the Atmosphere of B Lyre. 127 
the same line. No line has been admitted unless circumstances 
rendered its admission necessary. ‘The mean of each horizontal 
line has then been taken as the approximate wave-length. 
Throughout the observation the observer has absolutely no 
definite knowledge of the identity of any especial dot. Nor is 
it possible for him, while at the telescope, to connect one day’s 
work with another. Nor in tabulating is there any great 
chance for judgment. 
These appearances seem worthy to be classed as bright lines, 
for (1) they are seen as well with prism as with grating; (2) 
their number’ increases as the dispersion increases; (3) they 
occur for periods together, and are absent for periods together ; 
(4) they remain constant in position but vary in intensity; at 
times they are dazzling bright, and at times they are faded, 
scarcely noticeable; at times they remain a steady glare, at 
other times they sparkle in and out, are caught only in instants ; 
(5) these variations are not dominated by the weather, they 
may be bright or dull under the most favorable circumstances, 
and dull or bright under the most unfavorable. 
Our final list contains over a hundred and fifty positions ; 
some appear so few times that independently they could not be 
claimed as bright lines. Although probably correct to within 
two in the fourth figure, yet they are useless for purposes of 
identification. The number of observations, however, places a 
means of discriminating at our disposal. If those lines, which 
are capable of being referred to a single substance, varied to- 
gether, we may fairly consider that they belong to the same 
substance. 
In this way we have identified hydrogen, presenting in ad- 
dition to the four ordinary excitation lines to which we are 
accustomed, a large number, perhaps ninety, due to its low 
excitation spectra. 
Oxygen presents eleven lines of its high excitation spectrum, 
and in addition the glow of the negative pole represented by six- 
teen lines. 
Nitrogen presents probably eighteen lines of its high excita- 
tion spectrum, and in addition the glow of the negative pole 
represented by five lines. 
Carbon presents five lines, generally occurring together. 
Compounds of carbon and hydrogen present seven lines, gen- 
erally occurring together. Oxygen and carbon in combination 
present eight lines generally occurring together. Nitrogen and 
carbon in combination are probably represented by the most 
intense line of the cyanogen spectrum, but from the scantiness 
of the data we are unable to speak with certainty. 
Magnesium is represented by five lines generally occurring to- 
gether, and yet the traces of magnesium burning in hydrogen 
are very faint. 
