LOED OXMANTOWN ON THE GEE AT NEBULA IN OBION. 
78 
spectrum is extremely faint, except just at the nucleus, and even there it is pretty faint. 
When therefore we consider that a great part of the light of the Huygenian region of 
the nebula in Orion, the brightest parts of which are probably not much, if at all 
brighter than the nuclei of such nebulse as 2373, 2377, goes to form a gaseous spectrum, 
we can hardly expect that the remaining light could produce any but the feeblest conti- 
nuous spectrum. As a further confirmation of this view, it may be mentioned that on one 
occasion the spectrum of this nebula was examined in bright moonlight ; the light was 
so strong that the Huygenian region was scarcely visible ; in fact its boundaries were 
not more apparent than the boundary of the proboscis major at 131 is on a dark night ; 
yet although the three gaseous lines of the nebula were very fairly seen, no continuous 
spectrum from the moonlight, which was probably equal in intensity to the light of the 
nebula, could be detected. 
This observation, however, was not so satisfactory as I could have wished, as a haze 
which soon after eclipsed the nebula was beginning to come on at the time. 
Besides the central parts of the nebula, the nebula Mairiani was examined with the 
spectroscope, and a gaseous spectrum seen near the star 108. The proboscis major was 
also examined near 126, and a gaseous spectrum seen. / Orionis was also examined, 
but no spectrum but that of the star itself detected. 
A clock-movement for the 6-feet telescope is now in progress, and when this is com- 
pleted we hope to examine the spectra of this and other nebulae with more care. 
Memorandum. 
Through the kindness of Sir John Herschel I have been permitted to see his remarks 
on this paper, and gladly take advantage of his suggestions. The engraving is upon the 
whole very accurate ; a little more softening off in the faint outlying parts would have 
been desirable, but Mr. Basire did not think that it would be practicable consistent with 
the reasonable durability of the plate ; the forms, however, are correct. The sharpness 
of outline and the hard and marked character of the principal features are the result of 
the great light of the instrument ; with a diminishing aperture these characteristics gra- 
dually fade away. The engraving faithfully represents the object as it may be seen on 
any clear night, and the details are so well marked that no material change can take 
place hereafter which will not at once be recognized with an instrument of similar 
power. The interior of the trapezium has not been examined recently with the view 
to the question whether it is absolutely dark. With the 6-feet instrument the eye is so 
dazzled by the light of the four stars that it is difficult to form an accurate opinion ; 
and any nebulosity which may exist is probably too faint to affect the spectroscope. I 
am not certain that any part of the nebula is absolutely free from nebulosity, but the 
contrast is so great between the dark spaces alluded to by Sir John Herschel, and the 
contiguous portions of the nebula, that even in the drawing it was scarcely possible to 
indicate nebulosity so slightly as not to interfere with the proper gradation of light ; in 
fact it was scarcely possible to represent the bright parts sufficiently bright. 
MDCCCLXVIII. m 
