THE MOON'S ATMOSPHERE 63 



doubts about the moon's atmosphere, and the difficulties 

 experienced in accounting for the crown, "or else 

 concerning a meteor observed, not in our air, but in 

 the vapours that encompass the sun," might have 

 warned Dr. Halley and others to be especially watchful 

 when a total eclipse was due in Britain on April 22, 

 1715. Halley admitted the points named to be "very 

 singular, and deserving a great deal of attention." He 

 believed that a total eclipse of the sun had not been 

 seen in London since March 20, 1140 A.D. He passes 

 a gentle censure on the French astronomers for their 

 indifference to the total eclipse of 1706, but excuses 

 them on the ground that it was the first which " had 

 been observed with the attention the dignity of the 

 phenomenon requires." Strange to say, he made no 

 preparation to watch for " the blood-streak " and " the 

 luminous ring" that crowned the black body of the 

 moon, when the chance of seeing them again was 

 presented in 1715. They were seen and described by 

 him with a singular turning aside from facts to fables 

 about the moon's atmosphere, and the vapours that 

 were raised or the dews that fell on her surface. 

 Here is the account Halley gives of the red clouds 

 and the luminous ring in the eclipse of 1715: 1 



"A few seconds before the sun was all hid, there 

 discovered itself round the moon a luminous ring, 

 about a digit, or perhaps a tenth part of the moon's 

 diameter in breadth. It was of a pale whiteness or 

 rather pearl colour, seeming to me a little tinged with 

 the colours of the Iris, and to be concentric with the 

 moon, whence I concluded it the moon's atmosphere. 

 But the great height thereof far exceeding that of our 

 "Dews," Phil. Trans, xxix. p. 248. 



