Pritchet — Double Star Observations. 



301 



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

 ments are of poor defiaition ) measure distances systematically 

 larger than the average. 



3. Systematic diflferences 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. 



