KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 60- NIO 8. 37 



At the provisional determination of the magnitudes of the measured stars 

 Götz has employed Schiller's 178 photometric scale. According to this scale he 

 obtains at his measurement a number of 1198 stars brighter than the 16th magni- 

 tude. In counting plate B 265, he obtained within the same area 1050 stars, from 

 which follows, that the counted plate includes stars up to 15 w .so. Out of Hertz- 

 sprtjng's determinations of the photographical magnitudes of the central Pleiades 86 , 

 which closely agree with Chapman and Melotte's scale 36 , based upon the Harvard 

 Polar Sequence, we obtain from the 22 stars between 16 m ,oi — 16 m ,86, also measured by 

 Dugan 56 , the following systematic difference: 



^Hebtzspe. — m Dugan = + 1 m . 89 . 



As, further, in Dugan's scale, 14 OT ,48 corresponds to the magnitude 15 TO ,5o in 

 Schiller's, we finally obtain the result that Götz's counts include stars brighter than 

 the magnitude 16,37 in the polar sequence scale. 



If the number of stars per 49 squares [= l°xl°] in Götz's Table are summed up 

 for the part of the plate situated between a 0H3 m ,8 — Ä 26"\4 and S + 39° 0'— + 42° 1', 

 we obtain the following nnmbers: 



1474 1466 1498 

 1642 1571 1714 

 1614 1514 1579 



or, on an average, 1563 stars pr square degree. Using van Rhijn's table 164 , we 

 obtain, when the Andromeda nebula has a galactic latitude of — 21°, a limiting magni- 

 tude for the stars on Götz's plate equivalent to 16 m ,56, consequently in good accord- 

 ance with the determination performed above. 



If the supposition here made, that the nebula is farther away than the faintest 

 stars on Götz"s plate, is correct, the parallax of the nebula should be smaller than 

 the mean parallax for stars of the magnitude 16,5. There exists no determination 

 of this mean parallax, but if we extrapolate from Kapteyn's most recent determina- 

 tion of mean parallaxes 179 , we obtain: 



7r 16,5 = 0".000360. 



Measuring the positions of 517 small nebulse in the neigbourhood of M 33, Wolf 

 was struck by their peculiar distribution in relation to the nebula. He found that 

 the measured nebulse were grouped in chains which seemed to constitute an extension 

 of M 33:s spiral arms. In order to throw some light upon this remarkable discovery, 

 I ha ve with the aid of Wolf's catalogue drawn up a map representing the distribu- 

 tion on the plate of the examined nebulse. We there find how the nebulse seem to 

 emanate from the spiral arms and that between them channels free from every ne- 

 bula might be drawn on to the central nebula. It is of course not known, which 

 class of nebulse the measured objects belong to, but from their oblong form (Wolf's 



