THE SUN AND SOLAR PHENOMENA. 



61 



sun as seen from the earth, and the earth passes above or below her shadow. Owing to 

 the irregularity of the moon's motions, she does not cross the plane of the earth's orbit at 

 the same point in every revolution, but these points shift through a certain interval, after 

 which the same change is repeated, and the same cycle of eclipses occurs. This interval 

 is eighteen years and about eleven days, a period early discovered by the Chaldean 

 astronomers, and used for the purpose of foretelling eclipses. Thus, on the sixth of May 

 1845, there will be a solar eclipse, and if we add to this era the ecliptic period just named, 

 we are carried on to the seventeenth of May 1863, which will be the epoch of another. 

 The complete period is 6585 days, 7 hours, 42^ minutes nearly. But though the eclipses 

 of each cycle correspond, and may be regarded as identical with respect to the earth in 

 general, they vary in their appearances, and as to the localities in which they are visible. 

 There was an eclipse of the sun visible at the north pole in the month of June 1295, but 

 ever since, it has been proceeding more southerly. It made its first appearance in the north 

 of Europe in August 1367. It was central in London in 1601, which was its nineteenth 

 return; and nearly so again on the 15th of May 1836, its thirty-second appearance. At 

 its thirty -ninth return, in August 1880, the lunar shadow will fall south of the equator, 

 and continue receding from it, until its seventy-eighth appearance will be at the south 

 pole, on the 30th September, 2665. 



Baily prepared a table of all the eclipses of the sun that will be visible in this country 

 during this century ; only those are here taken from it which will impair more than half the 

 solar surface. The time and number of digits are calculated for the middle of England. 



The appearance which Nature puts on during a full solar eclipse is startling and 

 mournful ; and hence the idea was general, in ages of ignorance, that the event was 

 premonitory of real disaster. Virgil expresses the common opinion of his time with 

 reference to solar changes 



" The sun reveals the secrets of the sky, 



And who dares give the source of light the lie ? 



The change of empires often he declares, 



Fierce tumults, hidden treasons, open wars. 



He first the fate of Caesar did foretell, 



And pitied Rome, when Rome in Caesar fell." 



The last total eclipse visible in London was in the reign of George I. ; and there had 

 not been one seen in that locality since the time of the first Plantage.net. Halley has 

 left on record a striking account of that of 1715, from the pen of a correspondent, who 

 observed it from an eminence on Salisbury Plain. The account states: "It was the 

 most awful sight I had ever beheld in my life. "We looked in vain for the town of 

 Amesbury, situated below us ; scarcely could we see the ground under our feet. The 

 instant the eclipse became total, till the emersion of the sun, we saw Venus, but no other 

 stars. We perceived at this moment the spire of Salisbury cathedral. The clouds 

 not dispersing, we could not push our observations further : they cleared up, however, 

 considerably towards evening. I have hastened home to write this letter. So deep an 

 impression has this spectacle made on my mind, that I shall long be able to recount all 



