18 BOHLIN, ON THE GALACTIC SYSTEM WITH REGARD TO ITS STRUCTURE. 
from the Galactic zone is equally remarkable as the aggregation of clusters in the 
neigbourhood of the Galaxy. HSir WILLIAM HUGGINS view with regard to the pla- 
netary nebul&e was referred to above and contains nothing as tho their distribution. 
In several popular works the assertion of the distribution of the planetary nebulsae 
along the Milky Way is repeated. 
Such a close distribution along the Milky Way would meanwbhile prove to be 
contradictory to our hypothesis that the Galaxy and the Planetary Nebule are to 
be regarded as coordinated celestial objects. It became, therefore, important to take 
up the question of the distribution of the planetary nebulxe again. The charts thus 
constructed [Plate 31], involving all the planetary nebulxe of the New General Cata- 
logue, afford, indeed, no indication of an exclusive concentration of these bodies to 
the Milky Way. They show rather a somewhat uniform distribution of the planetary 
nebul& over the celestial sphere. By excluding the objects designed by H. as questi- 
onable, a slight tendency to gathering in respect to the Milky Way seems neverthe- 
less to become prevailing. : 
In this respect, it is further to be remarked that the nebule, denoted planetary 
and stellar in DREYER'S catalogue, are excluded from our statistics. It should further- 
more be noted that the classification of the planetary nebulg in HERSCHEL'S General 
Catalogue may be somewhat uncertain. I have, however, hitherto found no one 
object that seems to have been erroneously classed by Herschel as a planetary nebula. 
Thus the distribution of the planetary nebul&e seems rather to be in favour of our 
hypothesis on the relations of these bodies to our Galaxy than against it. 
9. On stellar nebulce. 
It is obvious that most of the stellar nebulz& are small planetary nebulze. TIt 
is, however, impossible to associate these objects with the statistics of the planetary 
nebulze, because they have not been investigated in a systematic manner. Most of 
these not very numerous objects have been found by R. COPELAND! and by E. OC. 
PICKERING” and are tested spectroscopically as gaseous bodies. COPELAND announces 
a few such objects, found in May and April 1883. In a short note, he adds five 
objects found by a number of sweeps over the heavens in the richer part of the 
Milky Way about Cygnus. 
PICKERING enumerates, in a short note, 11 stellar nebul&e between 18"25” and 
19: 20" of Right Ascension. The objects were discovered during an extensive exami- 
nation of the stars with the aid of a direct vision prisme. They are mostly undi- 
'R. Copeland, An account of some recent astronomical experiments at high elevations i the Andes. 
Copernicus Vol. III pag. 206. 
R. Copeland, Spectroscopic observations, made at the Earl of Crawfords Observatory, Dun Echt. Aber- 
deen, Monthly Notices, Vol. XLV pag. 90, 91. 
2 E. OC. Pickering, Small planetary nebule, discovered atthe Haward College observatory, The Observatory 
1882, pag. 294, 205. 
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