1. The Star Density on the Harvard Map. 



1. The Harvard Map. 



The discussion of tlie distribution of the stars to the eleventh magnitude which 

 these pages contains, is based on the photographic maj) of the intire sky pul)lisiied 

 by Harvard College Observatory and described in Circular N;o 71 from this ob- 

 servatory. 



Tliis photographic map, the Harvard Map, consists of a series of 55 glass 

 negatives. 



The photographs are taken with two small anastigmatic lenses, one mounted 

 at Cambridge U.S.A., the other at Arec[uipa, Peru, each having an aperture of one 

 inch and a focal length of about 13 inches. 



The eight by ten inches (30 by 25 centimeters) plates used for these instruments 

 cover more than thirty degrees square on the sky. Of the numerous photographs 

 taken with the two lenses a set of 55 plates have been selected and copied by 

 double contact print. 



The arrangement of the plates is to be seen in the following table, which 

 gives the centres of the negatives. The fourth column contains the duration of 

 exposure. 



The plates taken at Cambridge are indicated by the letters AC, those at Are- 

 quipa by AM. 



TABLE I. Catalogue of Plates. 



PI. 



R. A. 



D. 



Ex. 





PL 



R. A. 



D. 



Ex. 





PI. 





D. 



Ex. 







o''oo'" 



+ 90° 



39"' 



AC 



20 



2()''00"' 



+ 30" 



62"' 



AC 



39 



lo''0()"' 



-3(»" 



61 



AM 



2 



0 00 



4-60 



63 



AC 



21 



22 00 





69 



AC 



40 



12 00 





67 



a:\i 



3 



3 00 









0 00 





58 



a:m 



41 



14 (10 







AM 



4 



6 00 









2.3 



2 00 





60 



AM 



42 



16 00 





60 



AM 



5 



9 00 





59 



AC 



24 



4 00 





71 



AC 



43 



18 00 





60 



AM 



6 



12 00 





7t 



AC 



2h 



6 00 





78 



AC 



44 



20 00 





61 



AM 



7 



15 00 





58 



AC 



26 



8 00 





64 



AC 



45 



22 CO 





CI 



AM 



8 



18 00 





70 



AC 





10 00 





65 



AC 



46 





— (iO 



61 



AM 



9 



21 00 





60 



AC 



28 



12 00 





65 



AM 



47 







(-.4 



AM 



10 



0 00 



+ 30 



57 



AC 



29 



14 00 





73 



AC 



4S 



(i 00 







AM 



11 



2 00 



G2 



AC 



30 



16 00 





60 



AM 



49 



9 DO 





CO 



AM 



12 



4 00 





59 



AC 



31 



18 00 





60 



AM 



.50 



12 00 





72 



AM 



13 



6 00 





75 



AC 



32 



20 00 





60 



AM 



51 



15 00 





60 



AM 



14 



8 00 





59 



AC 



33 



22 00 





60 



AM 



52 



18 00 





61 



AM 



15 



10 00 





56 



AC 



34 



0 00 





(50 



AM 



53 



21 00 





60 



AM 



16 



12 00 





67 



AC 



35 



2 00 





61 



AM 



54 



0 00 



— 85 



60 



AM 



17 



14 00 





68 



AC 



36 



4 00 





68 



AM 



55 



14 00 



-75 



60 



AM 



18 



1(5 00 





64 



AC 



37 



6 00 





60 



AM 













19 



18 00 





56 



AC 



38 



8 00 





60 



AM 













