34 KNUT LUNDMARK, GLOBULAR CLUSTERS AND SPIRAL NEBULiE. 



by Shapley for the dependence on galactic longitudes of the globulars has also been 

 dotted. We find from this that spiral nebulse evidently concentrate in another di- 

 rection than globular clnsters. This circumstance does not exclude a correlation 

 regarding the galactic distribution betvveen the two kinds of objects but never- 

 theless makes the problem much more complicated. 



The conclusion resulting from these Apex-values, that the spiral nebulse and 

 the globular dusters are in some way related objects is also confirmed by the cir- 

 cumstance that Perrine has found nebulse near a number of globular dusters 147 . 

 Thus he finds, in the vicinity of: 



N. G. C. 7078 16 nebulse 

 7089 30 

 7099 31 



These nebulse are elliptical or circular, and spirals in such cases when the 

 structure has been plainly discernible. It must be more than a chance that so 

 many nebulse are to be found in the direction of these dusters. 



With regard to the plausible connection betvveen spiral nebulse and globular 

 dusters we are now going to examine the observations that might contribute to the 

 question of the distance of the spiral nebulse. 



III. The Parallaxes of Spiral Nebulae. 



Stephen Alexander 2 seems to have been the first who, taking Herschel's 

 star-gauges and Lord Rosse's at that time strongly doubted discovery of the spiral 

 forms of nebulse as a starting point, expressed the opinion, that the Milky Way is a 

 formation analogous to the spirals, which, consequently, are to he considered as remote 

 gigantic stellar systems. The theory of the Milky Way as a spiral vvas expressed 

 anew in 1870 by Proctor 159 , but the hypothetic spiral he constructed as an endea- 

 vour of explaining the structure of the Milky Way has, with respect to the 

 form, nothing to do with the structure observed in spiral nebulse. The theory of 

 the spiral form of the Milky Way has låter been exposed by Easton 59,60 in a series 

 of investigations. He has lately succeeded in constructing satisfactorily the form of 

 the Milky Way from the existing photographical material, supposing that it is a 

 spiral nebula of a form corresponding to a type intermediate between M 51 and 

 M 101 60 . 



The vievvs regarding the relation of spiral nebulse to the stellar system have 

 varied a great deal during the last few decades. Astronomers have sometimes been 

 inclined, in these objects, now to be found in so great a number, to see solar systems 

 just being formed (Moulton & Chamberlin 30 , See 187 ), sometimes very remote stellar 

 systems, »Island Universes>, Galaxies & C. (Curtis 00 , Very 224 and others), sometimes 

 nebulous vortices 24 and, quite lately, objects certainly remote, but nevertheless at 

 such distances that they form together with globular dusters and our stellar system 

 a gigantic world-unit, symmetrically distributed about the galactic plane 201 . 





