It seems rather risky to extrapolate our curves so far. But a million years are but a span in the life of the earth. Its records speak to us of many millions. The chalk cliffs of Dover took several million years to deposit on a former sea-bottom, and many more to rise to their present eminence. If there is a still farther advance in the life of the earth, what sort of direction can it take? Will a new race have arisen, as much above humanity as man is above the arboreal ape? Or will the further differentiation of man have come to a definite end, and progress be confined to an ever-increasing richness of intellectual, artistic, and emotional life? If there is any progress at all, it must be by _effort_, and the question could be answered with fair probability, if we could find an incentive to effort after the earth is entirely subdued. Such an incentive towards effort will lie in the ever-present danger of a celestial catastrophe, such as a collision with one of the smaller wandering planets or other denizens of outer space. It may be that the earth will by that time be alive to its own peril, and will take precautions! Its “grey matter”――our own descendants――will be confabulating and organizing in some great scheme of defence. The earth will have to adopt a Foreign Policy, if it is to be the master of its fate for all time. Here our dreams are checked by the realization that among the older planets of our solar system we can trace no activity attributable to a “foreign policy” of their own. But we must remember that ours is a small planet, which has very little influence upon its neighbours in space, and is certainly not a danger to them. If Mars, millions of years older than ourselves, has arrived at such a stage of advancement that it can think of transcending its own boundaries, it may make some attempt at communication, but the attempt might take the form which to us would be quite unrecognizable. Some observers thought that the persistent thunderstorms and magnetic disturbances experienced during the last opposition over wide areas were signs of such an attempt, but the coincidence may have been quite accidental. In any case, we cannot find any sign of the Martians having succeeded in exercising any powers beyond the surface of their own planet, though, if the “canals” really exist, their engineering feats must be truly stupendous. It may be that the earth, owing to its position between torrid Mercury and ice-bound Neptune, enjoys conditions specially favourable to mental and physical advancement. And so it may happen that it will for immense ages of time be the only planet to burst into consciousness. Thus it may at some epoch find itself the undisputed master of the solar system, and may be able to influence the other planets and make them subservient in some way to its own needs.