KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 60. NIO 8- 49 



From his measurements of internal motions in M 101 van Ma axen 121 derives a 

 common proper motion for the examined points and, consequently, for the nebula 

 as a whole: 



1*101 = 0",013. 



Lampland bas found for M 51, on an average, ;j. = 0",o8i. van Maanen at his 

 parallax-determination finds for ;x a , which is, according to Lampland, the greatest 

 velocity component the value 0",oo3. 



As a mean we thus obtain: 



For M 99 Lampland obtains 



"■99 



0",040. 



0" 8 043, 



a value which he consklers uncertain, and to which he does not assign any great 

 weight. 



The same author finds for N. G. C. 4594: 



•j... 



4594 



0",088. 



For N. G. C. 4565 and 7814 he does not find any trace of proper motion. 

 Summing up, we obtain: 



N. G. C. 224 



0" ; 018 



5194 



0.040 



4254 



0.043 



5457 



0.013 



4594 



0,088 



4565 



0,00 



7814 



0,00 



0",029 



Excluding the last two, we obtain ;x = 0".o40. 



It will be unnecessary to mention that the above values must be considered 

 as very uncertain, and that the authors themselves have made a reservation against 

 attaching too great importance to them. 



If we write down the formula (2) : 



~ m = 4.74 , ( f\ ( 13 ) 



K. Sv. Vet. Akad. Handl. Rand 60. N:o 8. 7 



