HERSCHEL THE DISCOVERER. 37 



by the famous gap in the Milky Way. The 

 Universe was, in fact, supposed to be a cloven 

 disc, and the Milky Way was merely a vastly 

 extended portion of it and not a region of 

 actual clustering. On this theory the clusters 

 and nebulae were supposed to be galaxies ex- 

 ternal to the Universe. Even in 1785, how- 

 ever, Herschel believed that there were regions 

 in the Milky Way where the stars were more 

 closely clustered than others. " It would not 

 be difficult," he wrote in 1785, "to point out 

 two or three hundred gathering clusters in our 

 system." 



Strange to say, Herschel's original ideas re- 

 garding the Universe were accepted for many 

 years by astronomical writers. Arago accepted 

 Herschel's original theory, unaware that he had 

 in reality abandoned it, and he was followed by 

 a host of French and English writers who did 

 not take the trouble to read each of Herschel's 

 papers, merely quoting that of 1785, and believ- 

 ing that it represented his final ideas on the 

 subject. Even Sir John Herschel seems to have 

 been unaware that his father gave up the disc 

 theory of the Universe. The famous German 

 astronomer, Wilhelm Struve, after an exhaustive 

 study of Herschel's papers, was enabled to prove 

 in 1847 that the theory had been abandoned 



