APPENDIX. TABLE ILLUSTRATING KEPLER'S THIRD LAW. (CHAMBERS.) IN the first column are the relative distances of the planets from the sun; in the second, the periodic times of the planets; and in the third, the squares of the periodic times divided by the cubes of the mean distances. The decimal points are omitted in the third column for convenience of comparison. The want of exact uniformity is doubtless due to errors in the observations. Arago, speaking of Kepler's Laws, says: "These interesting laws, tested for every planet, have been found so perfectly exact, that we do not hesitate to infer the distances of the planets from the sun from the duration of their sidereal periods; and it is obvious that this method possesses considerable advantages in point of exactness." TABLE OF THE PERIODIC COMETS. COMPILED BY LEWIS SWIFT, F.R. A.S., DIRECTOR OF WARNER OBSERVATORY, ROCHESTER, N. Y. QUESTIONS FOR CLASS USE. THESE are the questions which the author has used in his own classes for review and examination. In the historical portion, he has required his pupils to write articles upon the character and life of the various persons named, gathering materials from every attainable source. He has also introduced whatever problems the class could master, taking topics from the article on Celestial Measurements and the various mathematical treatises. INTRODUCTION.-Define Astronomy. Is the earth a planet? Is the moon a planet? What is the sky? Why does it seem concave? What gives it its color? What is the difference in the appearance of a fixed star and a planet? What is the Milky Way? In what direction does it span the heavens? In what season of the year is it most brilliant? I. THE HISTORY. 5-6. What can you say of the antiquity of astronomy? How far back do the Chinese records extend? Name some astronomical phenomena they contain. Why were these astronomers at fault in failing to announce the eclipse? (Ans. Certain religious ceremonies were performed on such occasions, and their omission was believed to expose the nation to the anger of the gods.) Why should the Chaldeans have become versed in this study? How ancient are their records? What discoveries did they make? How does the Asiatic differ from the Euro pean mind? 7. What Grecian philosopher early acquired a reputation in this science? What other discovery did Thales make (Physics, p. 251)? What did he teach? What memorable eclipse did he predict? What did Anaximander teach? In what century did Pythagoras live? What was his characteristic trait? Did he advance any proof of his system? Explain his theory. How does it differ from ours? What strange views did he hold? 8. When did Anaxagoras live? What did he teach? What theory did Eudoxus advance? What is the theory of the crystalline spheres? |