340 ANNUAL, REPORT SMITHSONIAN INSTITUTION, 1910. 



points in which there is need for work in southern skies could easily 

 be pointed out. Much work still remains to be done by those who 

 are not possessed of powerful instruments in the study of the brighter 

 variable stars and meteor radiants. Excellent photographs have been 

 made with the Bruce refractor at Arequipa, but the field of southern 

 nebular photography with reflecting telescopes is almost untouched 

 as yet, and there is no more urgent need for the astronomy of 

 the Southern Hemisphere than the establishment of a large re- 

 flector to continue for the southern skies the work done by Roberts, 

 Keeler, Perrine, and others on the northern nebulas and clusters, for 

 the study of faint variable stars, for parallax investigations, and 

 many other allied lines of research. A program of nebular photog- 

 raphy has been inaugurated with the new reflector at Helwan, Egypt; 

 its southern limit, however, will extend only to —40°. The day 

 must come, also, when there shall be established at some favorable 

 point in the Southern Hemisphere a large solar observatory to carry 

 on solar studies and investigations of the sun's constant of heat in 

 the southern summer season, thus supplementing the work of the 

 northern solar observatories. 



Above all, so few are the workers in this southern field compared 

 with the men and the instruments attacking the problems of the 

 northern skies, that some scheme of cooperation among southern 

 observatories seems imperative, each one to devote its attention to 

 some one line of work or some definite zone. Prof. Cooke, of Perth, 

 has recently pointed out the disadvantages arising from scattered 

 and unsystematic observations in meridian circle work, and has 

 announced that for the future all the efforts of Perth Observatory 

 in determining stellar positions will be concentrated upon the zone 

 from south declination 31° to 41°. Some such plan of cooperation 

 and delimitation seems essential for the future progress of as- 

 tronomy, and more particularly for the astronomy of the Southern 

 Hemisphere; as Prof. Kapteyn has pointed out, the scope of this 

 science to-day, with its millions of isolated units demanding study, 

 is too vast for the combined efforts of all the observatories of the 

 world, and he has accordingly suggested the well-known plan of 

 limiting future studies to certain relatively small " selected areas," 

 a plan which promises to be the best method of extending our 

 finite knowledge in a realm that is practically infinite. 



