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



43 



very plausible, not least because it admits of an explanation of the spiral form and 

 the frequent occurence of two spiral arms without resorting to any other expression 

 for the law of gravitation than Newton's. 



4. The spectral and photometric Researches concerning Spiral Nebulce. 



In 1898, Scheiner succeeded in obtaining a spectrogram of the Andromeda 

 nebula and thereby he found, in accordance with Sir W. and Lady Huggins, that the 

 nebula showed a continuous speetrum with absorption lines of the kind appearing in 

 stars of the Cr-type. Scheiner called attention to the fact that bis observations 

 might be explained by supposing the Andromeda nebula as a galactic system. 



Afterwards E. A. Fath 63 " 65 , Wolf 248 - 250 and Slipher 210 - 214 have with great 

 success devoted themselves to spectral researches of nebulse and we now know the 

 spectral type for 13 spirals. 



During the last few years Lundmark and Lindblad 110 have determined the 

 spectral types for nebulse by means of the effective wave-length method and obtained 

 the result that the examined spirals generally give Ä e ff. between 420 and 436'" 1 , corre- 

 sponding to the spectral classes G — K. We will here collect the results hitherto 

 published regarding the spectra and the effective wave-lenghts for objects known as 

 spiral nebula?. 



Table X. 



X. G. C. 



Observed 



type of 



speetrum 



Observera 



>eff. 



Speetrum 

 inferred 



Colour-index 

 inferred 



Magnitude 



(Holetschek) 



221 









432"" 



G, 



m 

 + 0,91 



ni 



8,7 



224 



G-K 



Wolf, 



Fath 



430 



G t 



+ 0,74 



5,0 



650,1 



G 



Fatii 





425? 



*v 



+ 0,45? 



9,4 



1023 



G 



» 











9,7 



1068 



G 



» 





420 



F 



+ 0,28 



8,7 



2841 









433 



K, 



+ 1,00 



9,1 



2903 









424 



F* 



+ 0,42 



9,0 



3031 



K 



Fatii 





433 



Ko 



+ 1,00 



8,0 



3034 









422 



F* 



+ 0,34 



8,8 



3623 









434 



A', 



+ 1,03 



8,9 



3627 









421 



F x 



+ 0,31 



8,6 



4214 



G? 



Slipher 









9,3 



4251 















9,5 



4449 



G 



Wolf, 



Slipher 









9,0 



4594 



F & , G 



Pease 



Fath 









8,7 



4725 



G 



Fath 





430 



G< 



+ 0,74 



8,7 



4736 



G 



» 





432 



G s 



+ 0,91 



7,7 



4826 



G 



» 





434 



K t 



+ 1,03 



8,G 



5194 



K 



» 





436 



K 3 



+ 1,U 



8,4 



5457,8 









431"" 



G t 



+ 0,82 



9,2 



7331 



G? 



» 











9,3 



