194 THE BORDERLAND OF SCIENCE. 



communication and a very odd interchange of light 

 one day one head being brighter and another the other 

 till they seem to have agreed 'finally to part com- 

 pany. The oddest part of the story, however, is yet to 

 come. The year 1852 brought round the time for 

 their reappearance, and behold ! there they both were, 

 at about the same distance from each other, and both 

 visible in one telescope.' 



In 1859, when the comet next came near the earth, 

 circumstances were such that it was useless to look for 

 it. In fact, it was so situated as to be lost in the sun's 

 light. But in 1866 the double comet should have 

 been well seen. In the confident expectation that both 

 comets would appear, astronomers carefully searched 

 the track which had been calculated for these bodies, 

 but without success. In some as yet unexplained 

 way both the comets had been either dissipated or 

 destroyed. 



Now, during the autumn of 1872, another period of 

 the comet's revolution was completed, and again a 

 search was instituted. Mr. Hind calculated the path 

 of the chief comet of the pair on three different suppo- 

 sitions as to the date of nearest approach ; more care 

 was expended in the search than in 1866 (when the 

 non-appearance of the comet took astronomers by 

 surprise) ; but all attempts to rediscover the comet 

 proved ineffectual, and it is now generally believed 

 among astronomers that Biela's comet will never be 

 seen again as a comet. 



I do not discuss here the probable manner or 



