CHAPTER XIV. IN THE DAYS OF THE CHALK In accordance with the view of the later story of the earth which was expressed on an earlier page, we now come to the second of the three great revolutions which have quickened the pulse of life on the earth. Many men of science resent the use of the word revolution, and it is not without some danger. It was once thought that the earth was really shaken at times by vast and sudden cataclysms, which destroyed its entire living population, so that new kingdoms of plants and animals had to be created. But we have interpreted the word revolution in a very different sense. The series of changes and disturbances to which we give the name extended over a period of hundreds of thousands of years, and they were themselves, in some sense, the creators of new types of organisms. Yet they are periods that stand out peculiarly in the comparatively even chronicle of the earth. The Permian period transformed the face of the earth; it lifted the low-lying land into a massive relief, drew mantles of ice over millions of miles of its surface, set volcanoes belching out fire and fumes in many parts, stripped it of its great forests, and slew the overwhelming majority of its animals. On the scale of geological time it may be called a revolution. It must be confessed that the series of disturbances which close the Secondary and inaugurate the Tertiary Era cannot so conveniently be summed up in a single formula. They begin long before the end of the Mesozoic, and they continue far into the Tertiary, with intervals of ease and tranquillity. There seems to have been no culminating point in the series when the uplifted earth shivered in a mantle of ice and snow. Yet I propose to retain for this period--beginning early in the Cretaceous (Chalk) period and extending into the Tertiary--the name of the Cretaceous Revolution. I drew a fanciful parallel between the three revolutions which have quickened the earth since the sluggish days of the Coal-forest and the three revolutionary movements which have changed the life of modern Europe. It will be remembered that, whereas the first of these European revolutions was a sharp and massive upheaval, the second consisted in a more scattered and irregular series of disturbances, spread over the fourth and fifth decades of the nineteenth century; but they amounted, in effect, to a revolution.