Page:The evolution of worlds - Lowell.djvu/255

Rh to lag behind, is torn two ways, and the friction acts as a break upon the body's rotation, tending first to turn it over if it be rotating backward and then to slow it down till the body presents the same face in perpetuity to its primary. The tides are the bulge, not simply those superficial ones which we observe in our oceans, and know to be so strong, but substantial ones of the whole body which we must conceive thus as egg-shaped through the action that goes on—the long diameter of the egg pointing somewhat ahead of the line joining its centre to the distorting mass. All the bodies in the solar system are thus really egg-shaped, though the deformation is so slight as to escape detection observationally. The knowledge is an instance of how much more perceptive the brain is than the eye. For we are certain of the fact, and yet to see it with our present means is impossible, and may long remain so.

Two concomitant symptoms follow the friction of the tidal ansæ: a shift of the plane in which the rotation takes place, and a loss of speed in the spin itself. The first tends to bring the plane of rotation down to the orbital plane, with rotation and revolution in the same sense. This effect takes place quicker than the other, and in consequence different stages may be noted in the creeping paralysis by which the body is finally overcome. Loss of seasons characterizes the first. For the coincidence of the two planes means invariability in the Sun's