( 122 ) 

 T A H r. E IV. 



Mean density of nebulae in the southern yal. hemisphere, 

 according to Stkatonoff. 

 (^4 including, B omitting the Xuhecidae). 

 A B 



If we consider wliat has been said aboxe on the incompleteness 

 of the observations also in the zone between 0° and — 20° gal. 

 latitude, little remains of the systematic increase as far as about 

 — 60° which, according to Stratonoff's table A, seems to exist. 



One more remark. An eminent obscr\er as John Hkrschel, 

 for the very reason that he naturally avoided the South Pole in 

 his "sweeps", is sure to have accounted for the incompleteness arising 

 from that circumstance and yet he says emphatically (Outlines, Ed. 

 1851, pg. 596) : "In the southern hemisphere a much greater uni- 

 formity of distribution prevails, and with exception of two very 

 remarkable centers of accumulation, called the Magellanic Clouds, 

 there is no very decided tendency to their assemblage in any parti- 

 cular region." 



We have, however, a means to lind indirectly whether the real 

 distribution of the nebulae with regard to the galactic plane is in the 

 main symmetrical, and consequently that the greater incompleteness 

 of the observations in the southern hemisphere is the cause that the 

 tables do not show a similar progression towards the galactic South 

 Pole as they do towards the galactic North Pole. 



The galactic equator and the celestial equator form a large 

 angle : 60^. A considerable segment of tlie northern galactic region 

 occurs south of the celestial equator — hence within the less thoroughly 

 investigated portion of the sky — ; on the other hand an equally 

 large segment of the southern galactic hemisphere lies within the 

 well-investigated region north of the equator. The strong influence of 

 the incompleteness of the observations (the real distribution of the 



