MOON'S ATMOSPHERE "RARE" 65 



Halley adds to this beautiful description that the 

 darkness was " more perfect," and the stars seen were 

 more numerous, in some places than in others; but 

 " the light of the ring was to all alike." From the 

 north of England, too, he heard "that the luminous 

 ring round the moon was seen there, which was 

 nowhere visible but while the eclipse was total " ! 

 Nine years before Halley conjectured that the cause 

 of the corona or ring lay, " probably, in those very 

 vapours, which produce that pointed light, that has 

 been observed lying in a manner along the ecliptic, 

 and that has the sun for centre," the zodiacal light. 



Into this traditional heritage of a lunar atmosphere 

 Herschel passed, till the blindness of unreasoning 

 belief was dispelled by facts. His atmosphere of the 

 moon, his three volcanoes on its surface, and its fitness 

 as a home for life, similar to what exists on the earth, 

 were long cherished beliefs, that had all to be un- 

 learned. Had the knowledge acquired from the total 

 eclipses of the sun in 1706 and 1715 not been laid on 

 the shelf and forgotten, he would not have fallen into 

 these mistakes. Unfortunately, though twentv-eight 

 solar eclipses occur every eighteen years somewhere on 

 earth, no total eclipse has been seen from our island 

 since 1715. A few years passed away, and, in 1792, 

 Herschel came to the conclusion that we " have great 

 reason to surmise that the moon's atmosphere," as well 

 as that of Saturn's fifth satellite, is " extremely rare." 



the moon's diameter. Its colour was quite white, not pearl colour, nor 

 yellow, nor red, and the rays had a vivid and flickering appearance, 

 somewhat like that which a gas-light illumination might be supposed 

 to assume if formed into a similar shape " (Astron. Trans, xv. p. 5). 



Halley's account of what he saw in 1715 is as distinct and vivid as 

 that of Baily in 1842. See also Lalande, ii. 443. 



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