Most of us have played at such ball games as bowls or billiards; and I have assumed that everybody knows something about golf. What happens in a game at bowls to the bowl which is not evenly weighted all through? It will not run straight. It has a bias. What happens to a billiard ball which is not perfectly round, or has lost its symmetry through age? It wobbles. And what happens to a badly made golf ball? That performs all sorts of exasperating antics. It ducks, it soars, it curls, it takes a slice. It also wobbles. Now that is exactly what the spinning, unevenly shaped globe which we call the earth has been doing for millions of years. It has been wobbling; and as we showed in the last chapter, it has always been trying to right itself. Thus the two poles have not always been in the same position; the oceans have not always been where they are. The waters have sometimes crawled up the land towards the poles and sometimes receded. Regions that have sometimes been frozen and cold have become warmer, and have covered themselves now with oceans, and now with forests, and now with deserts. There is no corner of the whole world which has not undergone changes of climate. These changes are very slow. There is no reason for supposing, in spite of the laments we sometimes hear about the loss of old-fashioned winters and old-fashioned summers, that the climate of England, for example, has changed in the least since Cæsar's legions landed on its shores. The Roman settlers in Britain doubtless experienced sloppy winters and wet summers now and again, just as we do; and King Arthur's knights, no doubt, had their saddening experiences of November fogs. Yet slowly and surely changes of climate do take place, and nothing except the winds influence them more than does the presence of a neighbouring sea or ocean. Most of us reckon the warmth of a locality's climate by the distance it is from the pole. That is, however, a very rough and ready method. Vladivostok is roughly the same distance from the North Pole as Venice; but there is a good deal of difference in the temperature of the two places. In Manchuria when the Russians and Japanese were entrenched before Mukden men died of cold and were frozen at their posts at a time when other people in Mentone and Monte Carlo, at the same distance from the Arctic Circle, were complaining of the heat. So that we see that it must not be assumed that a place like England (where for two thousand years we occasionally have had winters that would kill trees like eucalyptus or fig trees, and where oranges could never ripen in the open air) was always equally cold. It may have been, in fact we know it must have been, warm enough once to encourage and support what resembled a tropical vegetation. It must also have been at one time as cold as Siberia in the winter.