Page:The evolution of worlds - Lowell.djvu/294

252 upon the motion in the space permitted by Jacobi's integral, following Darwin's examination of this space. In the actual case of nature the effect is much more complicated, and at present is not capable of exact solution for masses other than indefinitely small, even supposing circular orbits for the chief bodies. It may, however, explain the curious relation shown in the arrangement of the direct and retrograde movement of satellites.