1877.) (ei | Draper. 
stances hitherto investigated in the sun are really metallic vapors, Hydrogen 
probably coming under that rule. The non-metals obviously may behave 
differently. It is easy to speculate on the causes of such behavior, and it 
may be suggested that the reason of the non-appearance of a dark line may 
be that the intensity of the light from a great thickness of ignited Oxygen 
overpowers the effect of the photosphere just as if a person were to look 
at a candle flame through a yard thickness of ignited sodium vapor he 
would only see bright sodium lines, and no dark absorption lines. Of 
course, such an explanation would necessitate the hypothesis that ignited 
gases such as Oxygen give forth a relatively large proportion of the solar 
light. In the outburst of 7 Corone Huggins showed that Hydrogen could 
give bright lines on a background of spectrum analogous to that of the Sun, 
However all that may be, I have no doubt of the existence of substances 
other than Oxygen in the Sun which are only indicated by bright lines. 
Attention may be called to the bright bands near G, from wave lengths 
4307 to 4337, which are only partly accounted for by Oxygen. Farther in- 
vestigation in the direction I have thus far pursued will lead to the dis- 
covery of other elements in the Sun, but it is not proper to conceal the 
principle on which such researches are to be conducted for the sake of per- 
sonal advantage. It is also probable that this research may furnish the 
key to the enigma of the D, or Helium line, and the 1474 K or Corona line. 
The case of the D, line strengthens the argument in favor of the apparent 
exemption of certain substances from the common law of the relation of 
emission and absorption, for while there can be no doubt of the existence 
of an ignited gas in the chromosphere giving this line, there is no corres- 
ponding dark line in the spectrum of the solar disc. 
In thus extending the number of elements found in the Sun we also in- 
crease the field of inquiry as to the phenomena of dissociation and recom- 
position. Oxygen especially from its relation to the metals may readily 
form compounds in the upper regions of the solar atmosphere which can 
give banded or channeled spectra. This subject requires careful investi- 
gation. The diffused and reflected light of the outer corona could be caused 
by such bodies cooled below the self luminous point. 
This research has proved to be more tedious and difficult than would be 
supposed because so many conditions must conspire to produce a good pho- 
tograph. There must be a uniform prime moving engine of two horse 
power, a dynamo-electric machine thoroughly adjusted, a large Ruhmkorff 
coil with its Foucault break in the best order, a battery of Leyden jars 
carefully proportioned to the Pliicker’s tube in use, a heliostat which of 
course involves clear sunshine, an optical train of slit, prisms, lenses and 
camera well focussed, and in addition to all this a photographic laboratory 
in such complete condition that wet sensitive plates can be prepared which 
will bear an exposure of fifteen minutes and a prolonged development. It 
has been difficult to keep the Pliicker’s tubes in order; often before the 
first exposure of a tube was over the tube was ruined by the strong Leyden 
_ sparks. Moreover, to procure tubes of known contents is troublesome. For 
