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 and masses of sedimentary rocks. There are first the Upper Palæozoic Rocks, and above these the geologists distinguish two great divisions. Next above the Palæozoic come the Mesozoic (middle life) rocks, a second vast system of fossil-bearing rocks, representing perhaps a hundred millions of swift years, and containing a wonderful array of fossil remains, bones of giant reptiles and the like, which we will presently describe; and above these again are the Cainozoic (recent life) rocks, a third great volume in the history of life, an unfinished volume of which the sand and mud that was carried out to sea yesterday by the rivers of the world, to bury the bones and scales and bodies and tracks that will become at last fossils of the things of to-day, constitute the last written leaf.

(It is, we may note, the practice of many geologists to make a break between the rest of the Cainozoic system of rocks and those which contain traces of humanity, which latter are cut off as a separate system under the name of Quaternary. But that, as we shall see, is rather like taking the last page of a book, which is really the conclusion of the last chapter, and making a separate chapter of it and calling it the last chapter.)

These markings and fossils in the rocks and the rocks themselves are our first historical documents. The history of life that men have puzzled out and are still puzzling out from them is called the Record of the Rocks. By studying this record men are slowly piecing together a story of life's beginnings, and of the beginnings of our kind, of which our ancestors a century or so ago had no suspicion. But when we call these rocks and the fossils a record and a history, it must not be supposed that there is any sign of an orderly keeping of a record. It is merely that whatever happens leaves some trace, if only we are intelligent enough to detect the meaning of that trace. Nor are the rocks of the world in orderly layers one above the other, convenient for men to read. They are not like the books and pages of a library. They are torn, disrupted, interrupted, flung about, defaced, like a carelessly arranged office after it has experienced in succession a bombardment, a hostile military occupation, looting, an earthquake, riots, and a fire. And so it is that for countless generations this Record of the Rocks lay unsuspected beneath the