( 694 ) 



There remain 168 nebulae. 



A good judgment about the accurac.v of the observations may be 

 obtained by the probable error derived by Mönnichmeyer for his 

 own observations on page 9. For the other observers I ha\e availed 

 myself of the data contained on pages 18 — 25. 



The accuracy was found little ditferent for the several observers 

 with the exception of Rümker. 



I therefore simply assumed the weights to be proportional to the 

 number of observations. For Rümker only the weiglit was reduced 

 in the proportion of three to one. For Schmidt the number of obser- 

 vations is not gi\'en. For reasons given by Mönnichmeyer they are 

 "immerhin etwas fraglich" (1. c. page 14). The results of Schmidt 

 got the weight of only a single observation for that reason. 



An overwhelming majority of the observations has been made 

 between 1861 — 1869 and 1883 — 1893. It was possible therefore in 

 nearly every case to contract all the observations in tioo normal 

 ditferences from which the proper motion and its weight could be 

 derived at once without any serious loss of accuracy. 



From these p.m. I then derived the components t and v, assuming 

 for the position of the Apex, the coordinates 

 yl75 = 273°, As = + 29°5. 



The whole of the materials was divided into the three classes of 

 Mönnichmeyer. They are described by him on page 9 of his paper 

 in the following way: 



Class I. Nebulae with starlike nucleus not fainter than 11''^ mag- 

 nitude ; 



Class II. Nebulae with moderately condensed nucleus not fainter 

 than ll'i^ magnitude; 



Class III. Difficult objects, in the first place irregular nebulae 

 without any sharply marked point ; furthermore all very faint objects 

 and the very oblong nebulae. 



Most of the objects have been classified by Mönnichmeyer himself 

 on page 9 of his paper. The nebulae wanting in this list have been 

 classified by myself, in accordance with the descriptions on p.p. 27 — 54, 

 as follows: h 693, 1088, 1225 in Class I; A 421, 1017, 1212, 1221, 

 1251, 3683 in Class II; h 316, 1461 in Class III. 



The p. m. as derived are relative p. m. ; they are the motions 

 relative to the comparison stars. Mönnichmeyer has investigated the 

 p.m. of the comparison stars themselves ; he has found a sensible 

 p.m. for only 7 of the objects used for my investigation. The 

 following table contains his results for these 7 stars. 



