They had at first a theory that the sea must once, in far back ages, have been a great deal higher than it is now.  But this explanation only brought about fresh difficulties.  It is quite impossible that the level of the sea should be higher in one part of the world than in another.  If the sea around England were then one or two hundred feet higher than it is now, it must have been one or two hundred feet higher in every part of the world where the ocean-waters have free flow.  One is rather puzzled to know where all the water could have come from, for such a tremendous additional amount.  Besides, in some places remains of sea-animals are found in mountain heights, as much as two or three thousand feet above the sea-level—­as, for instance, in Corsica.  This very much increases the difficulty of the above explanation.

So another theory was started instead, and this is now generally supposed to be the true one.  What if instead of the whole ocean having been higher, parts of the land were lower?  England at one time, parts of Europe at another time, parts of Asia and America at other times, may have slowly sunk beneath the ocean, and after long remaining there have slowly risen again.

This is by no means so wild a supposition as it may seem when first heard, and as it doubtless did seem when first proposed.  For even in the present day these movements of the solid crust of our earth are going on.  The coasts of Sweden and Finland have long been slowly and steadily rising out of the sea, so that the waves can no longer reach so high upon those shores as in years gone by they used to reach.  In Greenland, on the contrary, land has long been slowly and steadily sinking, so that what used to be the shore now lies under the sea.  Other such risings and sinkings might be mentioned, as also many more in connection with volcanoes and earthquakes, which are neither slow nor steady, but sudden and violent.

So it becomes no impossible matter to believe that, in the course of ages past, all those wide reaches of our continents and islands, where sedimentary rocks are to be found, were each in turn, at one time or another, during long periods, beneath the rolling waters of the ocean....

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These built-up rocks are not only called “Stratified,” and “Sedimentary.”  They have also the name of Aqueous Rock, from the Latin word aqua, water; because they are believed to have been formed by the action of the water.

They have yet another and fourth title, which is, Fossiliferous Rocks.

Fossils are the hardened remains of animals and vegetables found in rocks.  They are rarely, if ever, seen in unstratified rocks; but many layers of stratified rocks abound in these remains.  Whole skeletons as well as single bones, whole tree-trunks as well as single leaves, are found thus embedded in rock-layers, where in ages past the animal or plant died and found a grave.  They exist by thousands in many parts of the world, varying in size from the huge skeleton of the elephant to the tiny shell of the microscopic animalcule.