330 ANNUAL KEPORT SMITHSONIAN INSTITUTION, 1910. 



result of his stay of four years at the Cape of Good Hope in the 

 years 1751-1755; the noteworthy investigations made at the same 

 spot by Sir John Herschel, from 1834 to 1838; the expedition sent 

 to Santiago under charge of Gilliss in 1819 ; and others of more recent 

 date to which attention will be called later. 



The observatories in the southern part of the north temperate 

 zone can extend their investigations in many lines of astronomical 

 research to a distance of 30° to the south of the celestial equator 

 without great difficulty or loss of accuracy, but from this limit to the 

 South Pole we have a region amounting to about one-fourth of the 

 entire sky which, relatively to the northern skies, was almost as much 

 a terra incognita 75 years ago as was Central Africa at the same date, 

 and which to-day contains many virgin fields which offer rich returns 

 to the exploring astronomer. 



In the first great subdivision of astronomy, the astronomy of posi- 

 tion, whose field is primarily the determination of the accurate posi- 

 tions of the fixed stars, the observed changes in these positions are 

 so minute that the element of time becomes the most important factor 

 to enable conclusions to be drawn from a given mass of observations 

 as to the proper motions of the stars and the structure of the sidereal 

 universe as a whole. Because of this relatively short time factor 

 since the earlier exact observations of the positions of the southern 

 stars, the astronomy of precision of the Southern Hemisphere can not 

 yet compete with the results from the northern heavens. Sir David 

 Gill has said, and there is doubtless no more competent authority to 

 pronounce upon this point than he, that the state of our knowledge 

 of the exact positions of the stars of the Southern Hemisphere is at 

 least a century behind that of the Northern Hemisphere. Neverthe- 

 less, if we consider the results already secured in the exact cartogra- 

 phy of the southern skies, and take into consideration also the re- 

 searches in this field at present well under waj', we may safely reach 

 the conclusion that the coming 20 years will render our knowledge 

 of southern star positions very little inferior to those of the northern 

 skies, always excepting, in this conclusion, the disadvantage arising 

 from the lack of early observations, a lack which will necessitate the 

 accumulation of Results for many years before our knowledge of 

 southern proper motions can equal that of the northern stars. 



In this task of bettering our knowledge of exact star positions in 

 the Southern Hemisphere it is doubtless superfluous to mention here 

 the excellent work that has been done in the past and is now in 

 progress at a number of southern observatories, especially the exten- 

 sive results from Cordoba and the Cape of Good Hope. In 1865 the 

 Astronomische Gesellschaft undertook the extensive task of mapping, 

 by means of exact meridian observations, all the stars in the sky 

 down to the ninth magnitude. This work for the Northern Hemi- 



