KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 60. NIO 8. 63 



The tables XIV and XV, without aiming at completeness, contain the nebulse 

 that are known as spirals and for which observational data of the diameter d and m 

 are available. 



With the adopting of 



"Andr. 



0".0000050 



the absolute parallaxes have been derived from the diameter-values according to 

 the formula: 



7C = 0", 00000004 n d 



and from m according to the curve in Fig. 11. 



The values for m have been corrected for systematic errors in accordance with 

 Wirtz' discussion and reduced to Holetschek's scale. 



The values for the diameters are taken from the surveys of Pease, Fath, 

 Curtis, Knox Shaw, Bailey, Wolf and Kritzinger. The values given by Bailey 

 are corrected for systematic errors because B:s values are systematically too small. 

 The present writer has further measured the diameter from published photographs 

 and in a fevv cases from plates of his ovvn. 



It stånds to reason that the values for x m might be considerably changed by 

 future investigations, when more detailed observations will have been made regarding 

 the nebulae. I have nevertheless given the parallax- values in the tables, XIV and XV 

 in the hope that they might have some value as a first attempt of reconnoitring the won- 

 derful system of spirals which obviously seems to be connected with the globular dusters 

 and with the Milky Way, a connection, the nature of which is not yet satisfactorily known. 



Upsala, Astronomical Observatory, 15 th May, 1919. 



