( J20 ) 



of the nebulae with regard to the Oalaxy. Also Bauschinger (V. J. S. 

 24, p. 43) and Stratonoff adopted this syiniiietry. Stratonoff sup- 

 poses first that the skv from the North Pole to d — 20° has been 

 surveyed uniformly with a view to nebulae (1. c. p. 43); secondly 

 — like his predecessors — that the actually- observed decrease in 

 the number of nebulae between about — 50° and the South Pole 

 of the Galaxy must be ascribed to the incomi)leteness of the obser- 

 vations made in the southern hemisphere. 



I shall now proceed to demonstrate that Stratonoff's first surmise 

 is certainly erroneous and that the second, considering the present 

 state of our knowledge, is not justifiable and moreover improbable. 



That the nebulae-maferial from the North Pole to ff — 20° would 

 be collected with equal completeness throughout, as would follow 

 from Stratonoff's first sup|)Osilion, cannot, apart from the lack of a 

 systematic "Durchmusterung", be the case on account of the great 

 difficulty to detect faint objects like the nebulae, which arises from the 

 atmospheric absorption in regions far from tlie zenitli. In Lord Rosse's 

 telescope, for instance, if has never been possible to observe properly 

 the Omega nebula, though it lies only at — 16°. (Dreyer, Trans. 

 Dublin Soc, N. S. II p. 151). 



Besides, the circumstance tiiat the summer nights are never totally 

 dark in the relatively high latitudes of the observatories of the northern 

 hemispiiere where the nebidae observations have for t lie greater part 

 been ma(k\ must render the numbei- of catalogued nebuhxe in the 

 southern I'egions wiiicii then rise above our horizon much too small 

 in [)roportion to tlie oj)posite equatorial region. 



With regard to this I have investigated the tables of Bauschinger. 

 1 have compared two cipuilly large areas, occupying the same position 

 witii res|)e('t to the celestial equator and the Milky Way, .-I; «5'' to 

 9b, ,f _|_ 150 __ 3(r. B: a I7I' to 21'', rf -f 15' — 80°. " 



Tlie numl)er of bright and taint nebulae in those areas A and B 

 may be seen on table 111: 



TABLE III. 



i\'uiiihers of hriijlit <iii(l fdiiit iwhulin' in opposite equatoriid rtu/ions. 



A B 



bright nebulae .... 26 .... 20 



faint nebulae .... 157 .... 101 



There appears indeed to exist a difference at the expense of area 



