VARIATIONS OF LATITUDE. 



By E. Miller, University of Kansas, Lawrence. 



INHERE was published in the Astronomical Journal of No- 

 vember, 1891, an article on "The Variation of Latitude." 

 Its author was Mr. S. C. Chandler, an American amateur in as- 

 tronomy. The article- attracted the attention of the astronomical 

 world, and at once was subjected to fierce criticism from almost 

 every quarter. To-day, however, the question is no longer an open 

 one, for those who assailed it have, one by one, accepted it as es- 

 tablished beyond a doubt. 



In order to make clear what is to be said on the variation of 

 latitude, it is necessary to go back about 200 years, to ascertain 

 what was known and what was done along the line indicated by 

 the title of this paper. In 1693 there was born, in Sherbourn, 

 England, a child, James Bradley by name, who was to become one 

 of the greatest of astronomers. He was one of those who are not 

 content simply to amuse themselves with a telescope, but rather 

 had the ambition to do earnest work, and the spirit to choose a 

 problem which his predecessors for more than a century had failed 

 to solve. 



The Copernican theory that the sun is the center of the solar 

 system and that the earth moves round the sun established a cor- 

 responding apparent change in the places of the stars. The ab- 

 sence of any appreciable change in the position of the fixed stars, 

 when observed at opposite extremities of the earth's orbit, was one 

 of the earliest objections, as well as the most serious one, that had 

 been urged against the earth's motion ; and it was always considered 

 that the detection of such a change by observation would furnish ab- 

 solute proof that the earth is not the center of the solar system. In 

 the attempt to detect the annual parallax of the fixed stars, Bradley 

 made his famous discovery of the aberration of light. Its dis- 

 covery is universally regarded as one of the most important ad- 

 vances ever made in the field of astronomical science. The sa- 

 gacity of Bradley in the establishment of this law, as well as in the 

 detection of its physical cause, entitles him to a place among the 

 greatest philosophers of ancient or modern times. 



While at work investigating the phenomenon of aberration, Brad- 

 ley found that some stars near the equinoctial colure had a greater 



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