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.