MOUNT WILSON SOLAR OBSERVATORY. 



273 



natural to conclude that they must be very distant, consequently also 

 very luminous. A direct confirmation of the great distance is, how- 

 ever, exceedingly desirable. At Professor Kapteyn's request the obser- 

 vatories of the Cape of Good Hope and of Leiden courteously undertook 

 the observation of all the stars of these types not lately observed, for 

 which there are older observations promising a tolerable determination 

 of the proper motion. The new positions having been received, all 

 the observations, old and new, were collected and proper motions were 

 derived. From the parallactic motions the parallaxes were found as 

 shown in table 5. 



Table 5. 



For the N type another determination has already been obtained 

 from other data {Astrophysical Journal, 32, p. 93, 1910). The enor- 

 mous distances implied by these numbers will best be appreciated by 

 the comparison with similar determinations for other stars, given in 

 table 6, in which the older and newer determination for the N stars 

 are combined. 



Table 6. 



The last line relates to the stars called "c" by Miss Maury, occurring 

 in Boss's catalogue. Hertzsprung was the first to call attention to 

 the smallness of the proper motions of these stars. The determination 

 here given is by Hertzsprung and Kapteyn and is now published for 

 the first time. 



(3) Selected Areas. — Now that Mr. Seares's photometric researches 

 are approaching completion, it has seemed desirable to use his results 

 for obtaining statistical data for the whole sky down to the lowest 

 possible limit of magnitude. Such data based on a reUable photo- 

 metric scale have long been felt as one of the most urgent desiderata 

 in the study of the arrangement of stars in space. Accordingly photo- 

 graphs of all the Selected Areas from declination — 15° to the North 



