Page:The Solar System - Six Lectures - Lowell.djvu/31



their color. They are only red-hot. The Perseids move with medium velocity. They strike us on the quarter at twenty-five miles a second, and they are yellow. The Leonids, or November meteors par excellence, meet us head on at forty-three miles an houra second [sic], their swiftness giving them a bluish-green tint or a white heat. To Professor Newton again we owe our first step to knowledge of them. After the shower of the Leonids in 1866, he determined, from all the observations upon them, five orbits which they might have pursued; and then Adams, of Neptunian fame, from the motion of their node, showed that only one of the five, an orbit with a period of thirty-three years, would satisfy the problem. Thus was explained the similar shower of 1833 and the yet earlier one of 1799, seen by Humboldt. We should have had them again in 1900, but that Jupiter probably interfered. In the same way, the Andromedes prove to travel in an orbit whose period is thirteen years, and whose aphelion lies just outside the orbit of Jupiter. So, also, the Perseids pursue a closed orbit, but a much larger one, which takes them far beyond the orbit of Neptune. Shortly after Newton and Adams had worked out the path of the November meteors,