KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 60- N:0 8. 



Observer 



Wolf 



Pease 



Slipher 



Pease 



51 



Object 



Rotational 

 component 



Distance from 

 the nucleus 



M81 



100 km./ sec 



»Ne ar» 



N. G. C. 4594 



330 



120" 



» 



(600) 



120 



M31 



88 



121 



Mean 



173 



120 



Kostinsky has not stated at which distance from the nucelus the rotation 

 for M 51, found by him, is valid, but we may suppose, that it is for the distance 

 of 300". We obtain from Lampland's data \t. TOt = 0",025, and as a mean between the 

 values of van Maanen, Kostinsky and Lampland, [x rot = 0",03i. According to the 

 Table, F ro t= 173 km 7 8 ec, from which follows 



and 



X m = 0",000358 



^m = 0",ooo22i (employing Slipher's value for N. G. C. 4594). 



The measured u rot are probably too great. Tims Curtis 4 ' 5 , in examining the 

 proper motions of 66 large spirals has not been able to find any internal motion in 

 them. A decrease of ^ ro t would diminish the mean parallax, and our values for the 

 same may certainly be considered as upper limits. 



From Kepler's third law van Maanen derives the following relation between 

 the parallax and a central mäss which would cause a rotation of the magnitude he 

 has found for M 101: 



M = 0,0037 « 



-3 



With the adoption of our mean parallax 0",ooo22i we find a central mäss of 

 0,6 ■ 10 e O, where o designates the mäss of the sun. If we call to mind that Chap- 

 man and Melotte have estimated the number of stars in our stellar system to 2.10 9 , 

 and if we consider, that according to Russell's data 172 the stars ought to have on 

 an average a mäss not quite as great as that of the sun, we find that the results 

 regarding the masses seem to confirm the theory of the spirals as being remote galactic 

 systems. Their distances however tum out relatively small, but even a slight varia- 

 tion in \i would considerably change the value of ic m , which of course can only be 

 considered as a rough estimate. 



7. Wolfs Measurements of the Gaves in the Millcy Way and in the Spiral Nebula?. 



Supposing that the spiral nebulae are remote galactic systems of a structure 

 comparable with that of the Milky Way, Max Wolf 247 has, with every reservation, 

 given a way of deducing parallaxes for some of the large spiral nebulse. He assumes 

 that the so-called dark nebulse in the Milky Way (for instance the caves near and 



