Of these two factors, I need not say much about the first. It is about forty years since meteorological observations have been regularly and continuously made in this country and the results published in periodical reports, so that almost all requisite data pertaining to the climatology of Japan are at the disposal of the investigator. Assuming that the climate of Japan at present, which can be ascertained, not exhaustively perhaps, but scientifically enough, is not a widely different one from what it was in the past, there is the less need of dwelling upon the topic, so far as the scope of this book is concerned. I will content myself, therefore, with treating it very briefly. Generally speaking, it must be admitted that the ideal climate for the progress of civilisation must not be either a very hot or a very cold one; in other words, it must be a temperate one. At the same time, it is necessarily true that, for the sake of fostering a civilisation, the climate should be stimulative, that is to say, should be variable, but not running to such extremes as to impede the vital activity of the population. When a climate is constant and has no seasonal change, that climate, however mild it be, is very enervating, and not fitted for any strenuous human exertion, physical or mental, and is therefore adverse to the onward march of civilisation. Judged by this standard, the climate of Japan is a good one. If we put aside all the recently organised or annexed parts of the Empire, that is to say, Korea, Saghalen, Formosa, Loochoo, and Hokkaido, the remaining part, that is to say, the whole of historic Japan, which includes the three principal islands, was formerly divided into sixty-six _kuni_ or provinces, and stretches over a wide range of latitude, extending from 31 deg.--41.5 deg. N., so that the difference in temperature at its two extremes is very considerable. It must be remembered, however, that the difference is not so great as to necessitate totally different modes of living. In the province of Satsuma, for instance, the falling of snow can often be witnessed, while in Mutsu the temperature, in the height of summer, frequently climbs above 90 deg. F. The southern Japanese, therefore, can settle in the northern provinces quite comfortably without changing many of their accustomed habits, and the northerners, on the other hand, can shift their abode to the island of Kyushu, with very little modification in their ways of living. This almost similar way of living throughout the whole of historic Japan, with very slight local modifications only, is the cause why the unity of the nation was accomplished comparatively easily.