340 HH. Draper—Spectrum of the Nebula in Orion. 
During the month of March I have made two good photo- 
graphs with each of these arrangements. Those with the 
cult to get as good photographs of the nebula itself. On the 
contrary, those obtained with the slit spectroscope do not re- 
quire the same steadfast attention. 
The results derived from these photographs are interesting 
partly from what they show and partly from what they promise 
in the future. A number of photographs, under various con- 
ditions, will be needed for the full elucidation of the subject. 
The most striking feature is perhaps the discovery of two 
condensed portions of the nebula just preceding the trapezium, 
which give a continuous spectrum. At those places there is 
either gas under great pressure or liquid or solid. J have not 
been able to detect any stars of sufficient magnitude in these 
portions to produce this effect either in my photographs of the 
nebula or in any of the well known drawings of this object. 
It seems to me also that the photographs show evidence of con- 
tinuous spectrum in other parts of the nebula. In these 
respects the conclusions arrived at by Lord Rosse in his 
memoir (Phil. Trans. Royal Society, June 20, 1867, page 70), 
are to a certain extent borne out. 
he hydrogen line near G, wave-length 4340, is strong and 
sharply defined ; that at h, wave-length 4101, is more delicate, 
and there are faint traces of other lines in the violet. Among 
these lines there is one point of difference, especially well 
shown ina photograph where the slit was placed in a north 
and south direction across the trapezium; the H7 line, 4 4840, 
is of the same length as the slit and where it intersects the 
spectrum of the trapezium stars a duplication of effect is visi- 
ble. If this is not due to flickering motion in the atmosphere 
it would indicate that hydrogen gas was present even between 
the eye and the trapezium. I think the same is true of the 
He line, 44101. But in the case of two other faint lines in 
this vicinity I think the lines are not of the length of the slit, 
one being quite short and the other discontinuous. If this 
observation should be confirmed by future photographs of 
greater strength it might point to a non-homogeneous constitu- 
tion of the nebula though differences of intrinsic brightness 
would require to be eliminated. 
e April number of the American Journal of Science con- 
tains an account of a photograph of the spectrum of this neb- 
ula taken by Dr. Huggins. ave not found the line at 
2 3730, of which he speaks, though I have other lines which 
he does not appear to have photographed. This may be due 
