Page:The evolution of worlds - Lowell.djvu/132

102 hours and a half later. Then in May the variation vanished. More than one explanation has been put forward, but the best so far, because the most simple, is that the body is not a sphere but a jagged mass, a mountain alone in space, and that as it turns upon its axis first one corner and then another is presented to our view or throws a shade upon its neighbor. When the pole directly faces us, no great change occurs, especially if it also nearly faces the Sun. Yet even this fails to explain all its vagaries.

Eros is not alone in thus exhibiting variation. Sirona, Hertha, and Tercidina have also shown periodic variability, and it is suspected in others. Indeed, it would be surprising did they not show change. For they are too small to have drawn their contents into symmetry, and so remain as they were when launched in space. Mammoth meteorites they undoubtedly are.

With the asteroids we leave the inner half of the Sun's retinue and pass to the outer. Indeed, the asteroids not only mark in place the transition bound between the two, but stamp it such mechanically. In their own persons they witness that no large body was here allowed to form. The culmination of coalition was reached in Jupiter, and that very acme of accretion prevented through a long distance any other.

In bulk, the major planets compared with the inner or terrestrial ones form a class apart; and among the major