This section of the argument may however be adequately sustained, without having recourse to any such hypothetical illustrations as the foregoing. The astronomical attributes of the Earth, will even alone suffice our purpose. Consider first the effects of its momentum round its axis. There is the oblateness of its form; there is the alternation of day and night; there are certain constant marine currents; and there are certain constant aërial currents. Consider next the secondary series of consequences due to the divergence of the Earth’s plane of rotation from the plane of its orbit. The many differences of the seasons, both simultaneous and successive, which pervade its surface, are thus caused. External attraction acting on this rotating oblate spheroid with inclined axis, produces the motion called nutation, and that slower and larger one from which follows the precession of the equinoxes, with its several sequences. And then by this same force are generated the tides, aqueous and atmospheric. Perhaps, however, the simplest way of showing the multiplication of effects among phenomena of this order, will be to set down the influences of any member of the Solar System on the rest. A planet directly produces in neighbouring planets certain appreciable perturbations, complicating those otherwise produced in them; and in the remoter planets it directly produces certain less visible perturbations. Here is a first series of effects. But each of the perturbed planets is itself a source of perturbations—each directly affects all the others. Hence, planet A having drawn planet B out of the position it would have occupied in A’s absence, the perturbations which B causes are different from what they would else have been; and similarly with C, D, E, &c. Here then is a secondary series of effects: far more numerous though far smaller in their amounts. As these indirect perturbations must to some extent modify the movements of each planet, there results from them a tertiary series; and so on continually. Thus the force exercised by any planet works a different effect on each of the rest; this different effect is from each as a centre partially broken up into minor different effects on the rest; and so on in ever multiplying and diminishing waves throughout the entire system. * * * * *