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CHAPTER XI.

THE STORY OF A LUMP OF CLAY.

"CAIN: And those enormous creatures,

Phantoms, inferior intelligence

(At least so seeming), to the things we have passed,
Resembling somewhat the wild habitants

Of the deep woods of earth, the hugest which
Roar nightly in the forest, but ten-fold

In magnitude and terror; taller than

The cherub-guarded wall of Eden, with

Eyes flashing like the fiery swords which fence them,
And tusks projecting like the trees stripped of

Their bark and branches-what were they?

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The mammoth is in thy world;-but these lie
By myriads underneath its surface."

BYRON'S Cain.

N outline of the biography of even such a humble individual as myself will not be without interest. I need not introduce myself in learned mineralogical language; for there is not a boy living, old or young, who has not made practical experiments on me. But as clay is not limited to any geological formation, but occurs most abundantly in the later deposits, perhaps it may be as well for me to say to which period I belong.

In the older rocks, what was once clay has since

taken the form of slates or shales, subsequent alterations having brought about this change. I may say, therefore, that I belong to that period termed the Eocene-a period remarkable for the great influx of warm-blooded animals. This period is the first of that last great division of geological time called the Tertiary. Of these I shall speak presently.

The "London Clay," as it is termed, is the parent deposit of which I am elected spokesman and representative. London has been chiefly built out of this huge bed of clay; whence its geological name. I have a dark bluish-brown appearance, and in some places the fossils enclosed are assembled in great abundance.

Do not confound me with the clay beds which will be referred to by-and-by, and which belong to the Glacial or "Ice" period. No mistake could be greater, although very frequently our general appearance is much the same. It is when you compare the fossil remains found in our beds only, that you would form a just opinion. I was born ages before the clay above mentioned, and, although of marine origin, I came into the world under vastly different circumstances. When I was born, a nearly tropical climate existed in what is now Great Britain-when my neighbour was formed the climature was arctic. I made my appearance at the commencement of the Tertiary epoch-he did not come until the final close. Between this beginning and end, this extreme of warm and cold climates, a long period of time had elapsed,

marked by the deposition of thick strata, some of whose members will presently tell you what occurred meanwhile. But, from the time when I was formed to the present, I know there exists a gradual series of beds, in which fossil plants and animals are imbedded, whose types link those of the past with the present living fauna and flora of the globe.

Fig. 136.

The Eocene formation comprehends other strata than that of which I form a part, but I do not think I am egotistic in stating that ours is regarded usually as the principal member. The total thickness of these beds is over two thousand feet. The upper series are well developed in Hampshire and the Isle of Wight, where they bear evidence of having been deposited in fresh water. These are represented on the Continent by the beds of the Paris basin, famous to geologists as having yielded to Cuvier the first materials for the young science of comparative anatomy.

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Nummulites.

Section of ditto.

Taking the upper Eocene strata in England, you find a gradual transition from purely marine to purely fresh-water conditions, the Headon series containing shells and other organic remains usually found under both circumstances. The Bracklesham sands are crowded with fossil shells, chiefly of Turitella, indicating how slowly such beds must have

been formed, and how suitable was the ancient seabottom to the luxuriant development of these molluscs. I should also mention that underneath the London clay proper is a series of strata, chiefly of sands and gravels, ranging to a total thickness of nearly two hundred feet. My hearers who have carefully studied the geology of older formations, will see that a marked feature about these newer deposits is their very local extension. Whereas the older beds are almost world-wide in their distribu

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tion, the newer are so limited that it is very difficult to identify their exact position in different countries. Again, the principle of geographical distribution of animals and plants is felt more palpably in these newer than in the more ancient organisms. In the old rocks all over the world you see fossils common to them, but every stratum in the more recent deposits is marked by its own suite of shells, &c., just as every sea now possesses its own peculiar forms of life.

I was formed along the bottom of the sea, at no great distance from land, and yet far enough off for the sediment brought down by the rivers to have had its coarser particles precipitated before it reached the area over which my parent stratum was laid. Consequently, the muddy matter which there fell to the bottom was of a very impalpable character. The distant land was watered by large rivers, whose mouths debouched into the sea, and furnished it with the sedimentary material whose accumulation, to the thickness of nearly five hundred feet, ultimately formed the London clay. This land was clothed with a gorgeous and luxuriant flora, more like that fringing the banks of the Indian rivers, or the islands of the Malayan Archipelago, than any elsewhere growing in the world. Principal among the tropical forms were the palm-trees, whose graceful leaves hung over the water, and were reflected in its rippling depths. The succulent fruits of these palms fell in the stream in immense numbers, sometimes literally covering the surface, and were carried seawards. In some places where the clay was forming, these fruits, now known as Nipadites, accumulated to an extraordinary thickness, as in the Isle of Sheppy, where no fewer than a dozen species have been met with. In this locality alone, no fewer than one hundred and six species of plants have been found. You will see the correctness of my inference that an Indian climate and scenery existed in England during Eocene times by-and-by;

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