ASTRONOMY: CAMPBELL AND MOORE 
131 
ure suggest an encircling ring of materials whose principal plane, passing 
through the nucleus, passes also near our (the observers') position in 
space. These extensions terminate in condensed nuclei at equal dis- 
tances from the nucleus and on exactly opposite sides of the nucleus. 
The faint extensions and condensations may be and probably are largely 
the effect of the edge-wise projection of such a ring, as in the case of 
Saturn's rings when the observer is in the plane of the rings. The forms 
of the two terminating condensations, and especially the wing extending 
up and out from the east condensation, suggest that we are not pre- 
cisely in the plane of the assumed ring. 
PLANETARY NEBULA N. G. C. 7009 (COMPOSITE DRAWING, FROM CURTIS'S PHOTOGRAPHS 
OF THE NEBULA MADE WITH THE CROSSLEY REFLECTING TELESCOPE. THE SCALE IS IN 
SECONDS OF ARC) 
The form of the main nebula appears to be ellipsoidal and not chiefly 
elliptical. 
The space immediately surrounding the central nucleus appears to 
be relatively vacuous. Aside from the nucleus, the principal mass of 
visible nebulosity exists in the brilliant ring, roughly elliptical as to its 
inner and outer boundaries, which occupies the region about midway 
between the nucleus and the outer edge of the nebular structure. The 
brilHant ring is probably in reality an ellipsoidal shell: the projection 
of such a shell upon a plane at right angles to the line of sight would nat- 
