Now, if we find in various parts of the continents, and especially among the mountains, such strata sloping or "dipping" in various directions, sometimes only slightly, but sometimes very steeply,—nay, even standing up on end,—the conclusion that they have been upheaved and pushed or squeezed into these various positions by some subsequent process is irresistible. But this is not all; for in every mountain region we find that the rocks have been crumpled, twisted, and folded in a most marvellous manner. Solid sheets of limestone may be seen, as it were, to writhe from the base to the summit of a mountain; yet they present everywhere their truncated ends to the air, and from their incompleteness it is easy to see what a vast amount of material has been worn away, leaving, as it were, mere fragments behind. The whole geological aspect of the Alps (for example) is suggestive of intense commotion; and they remain a marvellous monument of stupendous earth-throes, followed by prolonged and gigantic denudation (see diagrams, chap. ix., p. [307]).

There are certain features found in all mountain-chains which must be carefully borne in mind, especially when we are considering the explanations that have been suggested with regard to their upheaval. These may be briefly stated as follows:—

  1. 1. Mountain-chains tend to run in straight or gently curving lines.
  2. 2. Their breadth is small compared to their length, and their height smaller still.
  3. 3. They rise sharply and are clearly marked off from the country on either side.
  4. 4. They form the backbones of continents.
  5. 5. The rocks of which they are composed have been greatly disturbed, folded, and contorted.
  6. 6. There is often a band of crystalline rocks (granite, gneiss, etc.) running along the centre of a high range.
  7. 7. They are connected with lines of volcanoes.
  8. 8. They are frequently affected by earthquakes.

Having arrived at the conclusion that the mountains show evident signs of upheaval, let us proceed to inquire whether any movements, either upward or downward, are taking place now on the earth, or can be proved to have done so within comparatively recent times. On this question there is ample evidence at our disposal.

More than one hundred and thirty years ago, Celsius, the Swedish astronomer, was aware, from the unanimous testimony of the inhabitants of the sea-coasts, that the Gulf of Bothnia was constantly diminishing both in depth and extent. He resorted to measurements in order to prove (as he thought) that the waters of the Baltic were changing their level. This was a mistaken idea; and we now understand that the level of the sea does not change, except under the influence of the daily rise and fall of the tide, which is easily allowed for. However, that was the idea then; and it survived for some time. But if the sea-level were continually sinking, the water, which, owing to the influence of gravitation, must always remain horizontal, would equally retreat all round the Scandinavian peninsula and on all our seashores. But this is not the case. Again, it would be impossible on this theory to explain the curious fact that in some parts of the world the sea is gaining on the land, while in other places it is as surely retreating; for we cannot believe that in one part the sea-level is rising, while in another (not far off in some cases) it is sinking. No body of water could behave in this irregular fashion; and the sea could not possibly be rising and falling at the same time.

Hence we may take it for granted that any change that we may notice in the relative level of land and sea must be due to upward or downward movements in the land.

But to return to Celsius. Old men pointed out to him various points on the coast, over which during their childhood the sea was wont to flow, and besides, showed him the water-lines which the waves had once traced out farther inland. And besides this, the names of places which implied a position on the shore, former harbours or ports now abandoned and situated inland, the remains of boats found far from the sea, and lastly, the written records and popular songs, left no doubt that the sea had retreated; and it seemed both to themselves and to the astronomer that the waters were sinking. In the year 1730 Celsius, after comparing all the evidence he had collected, announced that the Baltic had sunk three feet, four inches, every hundred years. In the course of the following year, in company with Linnæus, the naturalist, he made a mark at the base of a rock in the island of Leoffgrund, not far from Jelfe, and thirteen years afterwards was able to prove, as he thought, that the waters were still subsiding at the same rate, or a little faster. In reality, he had proved, not that the sea was sinking, but that the land was rising.

Similar observations show that nearly the whole of Scandinavia is slowly rising out of the sea. At the northern end of the Gulf of Bothnia the land is emerging at the rate of five feet, three inches, in a century; but by the side of the Aland Isles it only rises three and one quarter feet in the same time. South of this archipelago it rises still more slowly; and farther down, the line of shore does not alter as compared with the level of the sea.

But it is a curious fact that the extreme southern end of this peninsula is subsiding, as proved by the forests that have been submerged. Several streets of some towns there have already disappeared, and the coast has lost on the average a belt of land thirty-two yards in breadth.

The upward movement of the Scandinavian peninsula must have been going on for a long time, if we assume that it was always at the same rate as at present; for we find beds of seashells of living species at heights of six or seven hundred feet above the level of the sea. Great dead branches of a certain pink coral, found in the sea at a depth of over one hundred and fifty to three hundred fathoms, are now seen in water only ten or fifteen fathoms deep. It must have been killed as it was brought up into the upper and warmer layers of water. This is striking testimony.