NEWS FROM HERSCHEL'S PLANET. 12 7 



posed to lie very much nearer than the fainter ; and it 

 was because, being so much nearer, the brighter star 

 should be much more affected (seemingly) by the 

 earth's motion around the sun, that Herschel hoped to 

 learn much by studying the aspect of these unequal 

 double stars at different seasons of the year. He hoped 

 yet more from the study of such bright orbs as are 

 surrounded by several very faint stars. It was a case 

 of this kind that he was dealing with, when accident 

 led him to the discovery of Uranus. ' On Tuesday, the 

 13th of March (1781),' he writes, 'between ten and 

 eleven in the evening, while I was examining the small 

 stars in the neighbourhood of Eta in Gremini, I per- 

 ceived one that appeared visibly larger than the rest. 

 Being struck with its uncommon magnitude, I com- 

 pared it to Eta and the small stars in the quartile 

 between Auriga and Gemini, and finding it so much 

 larger than either of them, suspected it to be a comet. 

 I was then engaged in a series of observations (which 

 I hope soon to have the opportunity of laying before 

 the Royal Society) requiring very high powers, and I 

 had ready at hand the several magnifiers of 227, 660, 

 932, 1,536, 2,010, &c., all of which I have successfully 

 used on that occasion. The power I had on when I 

 first saw the (supposed) comet was 227. From experi- 

 ence I knew that the diameters of the fixed stars are 

 not proportionally magnified with higher powers, as 

 those of the planets are ; therefore I now put on the 

 powers of 660 and 932, and found the diameter of the 

 comet increased in proportion to the power, as it ought 



