LOED OXMANTOWN ON THE GEEAT NEBULA IN OEION. 
63 
the drawing, yet when once lost sight of they cannot be recovered again without return- 
ing to the brighter parts and tracing them in the preceding direction again. The great 
difficulty in tracing them, however, appears to he due, not so much to their extreme 
faintness, as to the uniform intensity of the nebulosity in this region; for when the 
nebula is examined with the equatoreal of 18 inches, a very low power capable of taking 
in a field of 1° being used, the whole sky in this region has a general luminous appear- 
ance when contrasted with the following and north following region, which itself is not 
entirely free from nebulosity. In drawing the greater part of the outlying regions of the 
nebula an eyepiece of a magnifying power of about 230 only, and having a field of 26', 
was generally used ; higher powers do not seem to show as much as the lower power, 
although with the higher powers the whole of the light from the large mirror is 
received into the eye, which is not the case with the lower power. With higher powers 
the field does not appear to be sufficiently large to allow of each streak of nebulosity 
being compared with the surrounding parts where the nebulosity is not quite so bright. 
The higher powers, however, bring out minute stars with ease which are hardly visible 
with the lower power. On the south preceding side the nebulosity appears to be much 
of the same character as on the preceding side ; long streaks have been traced from 1 VII 
and from a point about 3' or 4' south of it, which have been represented in the drawing 
just at their commencement. Another streak extends from the south side of 9 t through 
46 t , 46 n , which seems to extend considerably further than the drawing, — also another 
from t in a south following direction. 
It is probable that the drawing might be extended considerably further in various 
directions, but the nebulosity is of such extreme faintness that the work would advance 
very slowly, the eye requiring so long, after each exposure to even very feeble lamp-light, 
to recover its full power: 
** Form. 
Very little need be said on this subject as the drawing will speak for itself; it may, 
however, be well to call attention to the apparent connexion between some of the stars 
and the nebulosity near them. 
In some places the stars appear to have either repelled or absorbed the nebulosity, 
for instance at the trapezium, at 32 and 35, and 80 ; and in other places the nebu- 
losity is denser, as if the stars had attracted it, for instance at 2„ 4, 34, and 108. 
Around the star 108 the nebulosity seems to have a spiral character, and the same ap- 
pearance, though much less decided, may be seen round 4. Round the stars 46„ 46„, 
and 99j the nebulosity seems to have been concentrated, hut close to them there appears 
to be an absence of nebulosity; and in the case of 99 x the dark hole is situated excentri- 
cally with respect to the principal star, its nearer companion being close to the opposite 
side of the hole* ; but in the case of the double star 46j 46 n the hole is nearly symme- 
trically situated, but the nebulosity is brightest at the north preceding side. We can 
* A drawing of the nebulosity around < was published in the Philosophical Transactions for 1850, in which, 
the hole is well shown. 
