Furthermore, the beds in which these monstrous reptiles are entombed were overlaid by a stratum of calcareous ooze, now forming a solid mass of Chalk Rock, often a thousand feet in thickness. This Chalk, as we have seen, is nothing else than a vast accumulation of shells, so minute that millions of them would fit together on the blade of a small pen-knife, and hundreds of millions are carried about by every carpenter in his waistcoat pocket. How many generations of animalcules it took to pile up such an immense thickness of rock, by the action of their vital powers, and how many ages were consumed in the process it is beyond the reach of science to calculate, almost beyond the power of imagination to conceive. And yet the Chalk itself was followed by the various Formations of the Tertiary Age; while the last of these is separated by the Drift and Boulder Clay from the superficial deposits which correspond with the period of history, and which go by the name of Recent.
This topic has been illustrated in a lively and striking manner by Professor Huxley, in a Lecture delivered not long ago before the working-men of Norwich. “At Cromer,” he says, “one of the most charming spots on the coast of Norfolk, you will see the Boulder Clay forming a vast mass, which lies upon the Chalk, and must consequently have come into existence after it. Huge boulders of chalk are, in fact, included in the clay, and have evidently been brought to the position they now occupy by the same agency as that which has planted blocks of syenite from Norway side by side with them.
“The Chalk, then, is certainly older than the Boulder Clay. If you ask how much, I will again take you no further than the same spot upon your own coasts for evidence. I have spoken of the Boulder Clay and Drift as resting upon the Chalk. That is not strictly true. Interposed between the Chalk and the Drift is a comparatively insignificant layer, containing vegetable matter. But that layer tells a wonderful history. It is full of stumps of trees standing as they grew. Fir-trees are there with their cones, and hazel-bushes with their nuts; there stand the stools of oak and yew trees, beeches and alders. Hence this stratum is appropriately called the Forest-bed.
“It is obvious that the Chalk must have been upheaved and converted into dry land before the timber trees could grow upon it. As the trunks of some of these trees are from two to three feet in diameter, it is no less clear that the dry land thus formed remained in the same condition for long ages. And not only do the remains of stately oaks and well-grown firs testify to the duration of this condition of things, but additional evidence to the same effect is afforded by the abundant remains of elephants, rhinoceroses, hippopotamuses, and other great wild beasts, which it has yielded to the zealous search of such men as the Reverend Mr. Gunn.
“When you look at such a collection as he has formed, and bethink you that these elephantine bones did veritably carry their owners about, and these great grinders crunch in the dark woods of which the Forest-bed is now the only trace, it is impossible not to feel that they are as good evidence of the lapse of time as the annual rings of the tree-stumps.
“Thus there is a writing upon the wall of cliffs at Cromer, and whoso runs may read it. It tells us with an authority which cannot be impeached, that the ancient bed of the Chalk sea was raised up and remained dry land until it was covered with forest, stocked with the great game whose spoils have rejoiced your Geologists. How long it remained in that condition cannot be said; but the ‘whirligig of time brought its revenges’ in those days as in these. That dry land, with the bones and teeth of generations of long-lived elephants hidden away among the gnarled roots and dry leaves of its ancient trees, sank gradually to the bottom of the icy sea, which covered it with huge masses of Drift and Boulder Clay. Sea-beasts, such as the walrus, now restricted to the extreme north, paddled about where birds had twittered among the topmost twigs of the fir-trees. How long this state of things endured we know not, but at length it came to an end. The upheaved glacial mud hardened into the soil of modern Norfolk. Forests grew once more, the wolf and the beaver replaced the reindeer and the elephant; and at length what we called the history of England, dawned.
“Thus evidence which cannot be rebutted, and which need not be strengthened, though, if time permitted, I might indefinitely increase its quantity, compels you to believe that the Earth from the time of the Chalk to the present day, has been the theatre of a series of changes as vast in their amount as they were slow in their progress. The area on which we stand has been first sea and then land for at least four alternations, and has remained in each of these conditions for a period of great length.
“Nor have these wonderful metamorphoses of the sea into land, and of land into sea, been confined to one corner of England. During the Chalk Period not one of the present great physical features of the Globe was in existence. Our great mountain ranges, Pyrenees, Alps, Himalayas, Andes, have all been upheaved since the Chalk was deposited, and the Cretaceous sea flowed over the sites of Sinai and Ararat.
“All this is certain, because rocks of Cretaceous or still later date have shared in the elevatory movements which gave rise to these mountain chains, and may be found perched up, in some cases, many thousand feet high upon their flanks. And evidence of equal cogency demonstrates that, though in Norfolk the Forest-bed rests directly upon the Chalk, yet it does so, not because the period at which the forest grew immediately followed that at which the Chalk was formed, but because an immense lapse of time, represented elsewhere by thousands of feet of rock, is not indicated at Cromer.
“I must ask you to believe that there is no less conclusive proof that a still more prolonged succession of similar changes occurred before the Chalk was deposited. Nor have we any reason to think that the first term in the series of these changes is known. The oldest sea-beds preserved to us are sands and mud and pebbles, the wear and tear of rocks which were formed in still older oceans.”[105]