HOW TO WEIGH THE SUN. 689 



course on the earth about 1700; visible as a total eclipse in our latitude, June 16, 

 1806; becomes annular again about 1968, September 22d, and finally passes off 

 or leaves the earth, at the north pole, May 11, 2347. 



Hence this eclipse will have continued its eighteen-year visits to the earth 

 during 1298 years and two months; having made itself visible on some part of 

 the globe seventy-three times — making seventy-two complete Saroses. When it 

 first struck the earth in 1049, it appears that the sun was 16° 13' east of the 

 moon's descending node ; and when it leaves the earth in 2347, that the sun will 

 be 17° 12' west of the same node; having gone backward through an arc of 33° 

 25' of the moon's orbit, which in this case would seem to be the "ecliptic limit." 

 Now as the sun will have retrograded (with reference to the Saros) 33° 25' in 

 1298 years, to go around the remaining part of the moon's orbit, /. e., 360° 00' 

 — 33° 25'=326° 35', will take 12,687 years, the time that must elapse before this 

 eclipse can fall on the earth again. Now, these results being only those of my 

 own investigation, I do not claim absolute accuracy for them, but feel satisfied 

 that the most elaborate computer will not find them greatly in error. 



In contemplating that about forty-one such eclipses as this, and twenty-nine 

 eclipses of the moon, are each one all the time making their periodical rounds of 

 eighteen years about the earth, there might seem, at first view, to be an irregular 

 and uncertain clashing, as it were, of dates and shadows, with other phenomena 

 of eclipses, which could hardly be reconciled. But it is a fact absolute, that the 

 various and intricate motions of the earth and moon are so well known that their 

 positions with each other and the sun can be obtained at any time ; and thus the 

 dates of all these seventy eclipses foretold to within a few seconds of the times of 

 their occurrence, for many years in the future. 



"Great and marvelous are thy works, Lord God Almighty. Just and true 

 are thy ways, thou King of Saints." 



HOW TO WEIGH THE SUN. 



BY EDGAR L. LARKIN, NEW WINDSOR OBSERVATORY, ILL, 



There are several methods, and we select the most elementary in the at- 

 tempt to make the case clear by the use of words instead of mathematical sym- 

 bols, if such a thing is possible. Useless sentences must be written where, if the 

 subject were treated mathematically, a few Greek letters and algebraic formulas 

 would express all in clearer terms. What we shall say is intended to assist youths 

 just beginning to expand their minds in the study of astronomy ; and we will 

 be pleased to receive letters from all such students between the ages of twelve 

 and seventeen years, who have read this article and are interested in the noblest 

 of all sciences. 



Gravity. — If a body at rest begins to fall, it will fall sixteen and one-twelfth 

 feet, or 193 inches, the first second ; but at the end of the second, it will be moving 

 at the rate of thirty-two and one-sixth feet, or 386 inches, per second. Among 



