Priteket — Double Star Observations. 



301 



2. A small per cent of observers (generally when the instru- 

 ments are of poor definition ) measure distances systematically 

 larger than the average. 



3. Systematic differences in measures of position-angle 

 seem less serious than in measures of distance. In other 

 words the errors in measurement of position-angle seem 

 mostly accidental. 



In illustration the following comparison of the measures of 

 two observers is added. The observations were made by my 

 father and myself in 1880-81, and as the observations refer 

 to practically the same epoch, they are strictly comparable. 

 In the table which follows P denotes C. W. Pritchett and H 

 denotes H. S. Pritchett and the results are given in the sense 

 P-H. 



COMPARISONS OF MEASURES OF DISTANCE. 



Number of 



20 

 35 

 35 

 32 



Below 1 ".5 

 1 ".5 to 3 ".0 

 3".0to 6".0 

 Above 6".0 



PerEq. (P-H). 



+ ".13 

 + .12 

 -f .15 

 -f .13 



COMPARISONS OF MEASURES OF POSITION-ANGLE. 



