172 HERSCHEL AND HIS WORK 



a musician in Bath, ll.-rsch.-l " fuiin.l that the poles of 

 Mara were distinguished with remarkable luminous 

 He believed that, by observing them carefully, 

 are a key to a knowledge of the planet, 

 and its history, the length of its day, its atmospln >< . 

 its MMQBft Th<-M- < ,l.s-r\ at inns were continuc.l during 

 six or seven years. Sometimes he saw a \v< -ll-mai -U. ! 

 lucid Hpot on Mars: "it is its south pole, for it remains 

 in the same place, while the dark equatorial spots 

 perform their constant gyrations : it is nearly circular. 

 It was not only circular; "it was very brilliant 

 white." At other times he saw also another " lucid 

 spot" at the planet's north pole. Occasionally both 

 spots were seen, but the one was "thicker," or "much 

 thicker," than the other, while the thinner was, or 

 seemed to be, longer. After six years of watching h. 

 writes, " The white polar spot increases in size ; it is 

 very luminous." The conclusions he drew from i 

 notes in his journal, and from his calculatioi 

 ascertain the seasons on Mars, must have been listened 

 to by those who first heard them read as if they were 

 a page or two from a romance by Fielding or SmolKtt. 

 We give them in Herschel's own words. 



" The analogy between Mars and the earth is, perhaps, 

 by far the greatest in the whole solar system. ... If 

 then we find that the globe we inhabit has its polar 

 regions frozen and covered with mountains of ice and 

 snow, that only partly melt when alternately exposed 

 to the sun, I may well be permitted to surmise that 

 the same causes may probably have the same effect on 

 the globe of Mars; that the bright polar spots are 

 owing to the vivid reflection of light from frozen 

 regions : and that the reduction of those spots is to be 



