KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 43. N:o 10. Tl 
dices in the form of lateral jets of nebulosity as for example the nebula G. C. 1532, 
Plate 4 N:o 7. In order to explain these closed forms of planetary nebul&e as 
products of exaggerated matter, originally contained in a superficial hide or shell, as 
above mentionned, it is to be supposed that the evolution of such nebul&e is far 
more advanced than in the case of the proper ring nebule. Thus, in some cases, the 
ring itself proves to be condensed to a more cloudy form of a striking resemblance 
to a Via Lactea." But in most cases, even such a remainder of the primitive shell 
has vanished, either by gathering to an atmosphere around the general centre of the 
nebula as in G. OC. 4234 and G. C. 4514 or in giving off so much of its light as to 
be quite invisible. In fact, the prolonged exposure of some objects of this kind, 
extended for example to 4 hours for G. C. 1532, does not bring out any trace of 
atmosphere or Via Lactea. 
It is to be noted, that these closed nebul&e are generally very bright, with a 
colour of blue, verging upon green. 
A most interesting form of planetary nebula is exhibited by the above men- 
tioned G. C. 3258, Plate 5 N:o 3. This nebula has a big central nucleus, the 
atmosphere of which proves to be separated from the nucleus, forming around the 
centre a cloudy peripheric ring, irregularly deformed and broken as to have the 
appearence of a Milky Way, surrounding the central body of the nebula. 
6. The distribution of stars in the Galactic System. 
In the Vol. 31, 1817 of the Philosophical Transactions, in the Concluding re- 
marks (p. 330) to Astronomical observations and experiments tending to investigate the 
local arrangement of the celestial bodies in space amd to determine the extent and condi- 
tion of the Milky Way, W. HERSCHEL expresses as his opinion that » What has been said 
of the extent and condition of the milky way in the several papers on the construc- 
tion of the heavens, with the addition of the observations, contained in his attempt 
to give a more correct idea of its profundity in space, will nearly contain all the 
general knowledge we can ever have of this magnificent collection of stars». The 
results, referred to with these words, and the proceeding of research are well known. 
The instrument employed was the 20-feet reflector of 19 inches aperture. H. selected 
a pretty broad stripe crossing the milky way at right angles and counted the num- 
bers of stars in 3400 fields of view belonging to the stripe at six different zones, the 
total number of stars of the heavens, thus estimated, amounting to 20 millions, of 
which 18 millions in the Milky Way itself. In the same manner, J. HERSCHEL 
counted 2299 fields of view of the southern hemisphere. It was concluded from these 
gauges that the: stars, if supposed uniformely distributed, are arranged together in 
a body, the boundaries of which form a lens, whose greatest and smallest dimen- 
sions have the ratio of 5.5 to 1. In the further progress of his researches (Memoir 
GROT 3258: Plate 5. N:0. 3, 1S an examplesof. this kmd, 
