52 ROUGH WAYS MADE SMOOTH. 



planet near Theta, and of this star which he took for Zeta, 

 he says, ' they were probably really brighter [than the 4^ 



Suggested explanation of Watson's 

 and Swift's observations. 



and 3^ magnitude respectively], because the illumination of 

 the sky was not considered in the estimates.' Before he had 

 thoroughly examined the pencil marks on his card circles, 

 and made the necessary calculations, he supposed the brighter 

 star to be Zeta, because he did not see the latter star. But 

 when he examined his result carefully, he found that the 

 bright star was set (according to his pencil marks) more 

 than one degree east of Zeta. Writing on August 22, he 

 says, * The more I consider the case the more improbable it 

 seems to me that the second star which I observed, and 

 thought it might be Zeta, was that known star. I was not 

 certain, in this case, whether the wind had disturbed the 

 telescope or not. As it had not done so in the case of any 

 other of six pointings which I recorded, it seems almost 



Fig. 4. Showing all the stars observed by Watson and Swift. 



certain that the second was a new star.' It would be easy 

 to understand why Professor Watson had not seen Zeta, for 



