Page:The Solar System - Six Lectures - Lowell.djvu/134

 VI COSMOGONY

the present, the past. The forces that the we have found to be moulding the system to-day must be those that fashioned it earlier. Given, therefore, the condition at the moment, if we apply to it the forces now at work reversed, we shall get the condition that was.

Similarly, we can cast its horoscope for the future, by Taylor's theorem. Unfortunately, the problem is so complicated that no solution, even approximately satisfactory, has yet been obtained; but that the mystery baffles us renders it all the more fascinating.

In the solar system, as we find it to-day, are several remarkable congruities which are quite independent of gravitation, and bespeak a cause.

I. The central body is much larger than its attendants.

II. The planets move in orbits nearly circular.

III. They travel nearly in one plane.

IV. And in the same sense (direction).

As for the planets themselves—