62 HERSCHEL AND HIS WORK 



not broad the twelfth part of the diameter of the moon. 

 This planet did appear very black, and her disk very 

 well defined, within the whiteness, which encompassed 

 it about, and whose colour was the same with that of 

 a white crown or halo, of about four or five degrees 

 in diameter, which accompanied it, and had the moon 

 for its centre. ... A little time after the sun had 

 began to appear again, the whiteness and the crown, 

 which did encompass the moon, did entirely vanish." * 

 Duillier's comment on this description of the corona is : 

 " The moon's atmosphere cannot well be supposed less 

 than of 130 miles, in perpendicular height. . . . Though 

 it was very plain that the atmosphere of the moon 

 must needs show itself, in the time of a total eclipse 

 of the sun; yet I do not know that anybody did 

 think of this, till in the last month of May, many 

 persons did actually see it." 2 



At Zurich Dr. Scheuchzer, in four lines of Latin, 

 describes how they had a solar eclipse, at once total 

 and annular; total, because the sun was wholly 

 covered by the moon ; annular, not properly so called, 

 but by refraction, since around the moon appeared a 

 ruddy brightness (fulgor rutilans), caused by rays 

 refracted through the moon's atmosphere. 



The blood-red streak, the corona, the ruddy bright- 

 ness observed during the total eclipse of 1706, the 



1 A letter from a friend at Marseilles informed Duillier that, during 

 totality, "there did remain one bright digit, all about the globe of the 

 moon " (Phil. Trans. (No. 306), p. 2237). 



2 "The red prominences were first seen during the solar eclipse of 

 8th July 1842 " (Proctor, JEncyc. Brit. vol. ii. p. 788). Baily was not 

 the first to see them. Captain Stannyan and Dr. Scheuchzer carried off 

 the honour 136 years earlier. Facio Duillier has the credit of first 

 describing the corona. 



