It is therefore quite clear that these columns must have been under water to a depth of twenty feet or so, and also that they must have remained under water for some considerable time, during which the shell-fish made these borings. Then an upheaval took place whereby the whole building was elevated to its present level. But underneath the present floor, at a depth of five feet, were discovered the remains of an older floor. This probably belonged to an earlier building which had in like manner been depressed below sea-level. We thus learn that the land in this spot had been sinking for a long time, and that at some subsequent time it rose. The fallen columns suggest the idea that they were thrown down by earthquakes. At the present time the land here is again sinking at the rate of one inch in three or four years. But the first example of upheaval within comparatively recent times, and one which is instructive as throwing some light on the subject of the present chapter,--namely, the upheaval of mountain-chains,--is to be found along the western mountainous coast of South America. Here we have the magnificent ranges of the Andes running along the whole length of this continent. The illustrious Charles Darwin, during his famous trip in the "Beagle," discovered numerous raised beaches along this coast, and at once perceived their importance to the geologist. The terraces are not quite horizontal, but rise towards the south. On the frontier of Bolivia, they are seen at heights of from sixty-five to eighty feet above sea-level; but nearer the higher mass of the Chilian Andes they are found at one thousand feet, and near Valparaiso, in Chili, at thirteen hundred feet above the sea. Darwin also discovered that some of the upheavals thus indicated took place during the human period; for he found in one of the terraces opposite Callao, in Peru, at a height of eighty feet, shells with bones of birds, ears of wheat, plaited reeds, and cotton thread, showing that men had lived on the terrace. These relics of human industry are exactly similar to those that are found in the _huacas_, or burial-places, of the ancient Peruvians. There can be no doubt that the island of San Lorenzo, and probably the whole of the coast in its neighbourhood, have risen eighty feet or more since the Red Man inhabited the country. Callao probably forms the northern limit of the long strip of coast that has been upheaved, and the island of Chiloe the southern limit; but even thus the region of elevation has a length from north to south of about 2,480 miles. We noticed in the case of Scandinavia that the upward movement is greater in the interior of the mountain-range than at or near the coast; and it is interesting to find that the same difference has been observed in the case of the Andes. The upheaving force, whatever its nature, acts with more energy under the Chilian Andes than under the rocks of the adjacent coast.