But I must not weary the reader by dwelling on this monotonous repetition of catastrophes--for must they not have been catastrophic if such ups and downs of whole continents are crowded within the human period? We may allow a number of thousands of years for Man's possible existence, but Archaeology and History alike protest against the =millions= of years required to explain these continental oscillations on any basis of uniformity. One such period of horror ought to be enough for us, and to understand or explain it in a truly scientific manner, we must with it correlate the sudden and world-wide change of climate already described. One more point demands consideration ere we complete this subject of what Man has witnessed of geological change. For, according to current theory =almost all the mountains have been either wholly formed or at least completed within quite "recent" times=: indeed many of the greatest mountain chains have been puckered up from the position of horizontal strata wholly since "Miocene times," which for us means since Man was upon the globe. Thus Dana in speaking of the part of Western America which has been elevated since "Miocene times," says that it-- "... probably included the whole of the Pacific mountain border, from the line of the Mississippi Valley to the Pacific coast line and outside of this line for one or more scores of miles."[91] And he adds the significant words: "Contemporaneously, similar movements were in progress over the other continents: along the Andes, affecting half, at least, of South America; the Pyrenees, Carpathian Alps, and a large part of Europe; the Himalayas and much of Asia." (p. 365.) Let us now take a brief glance at a few of the details of what these mountains were thus doing while Man was living in semi-tropical England, or at least Western Europe. In speaking of foreign examples of Tertiary mountain-making this author devotes especial attention to the Alps and the Juras, for their structure is better understood, having been more carefully studied. And of an example described by Heim, already spoken of, he says: "One of the overthrust folds in the region has put the beds upside down over an area of 450 square miles. Fifty thousand feet of formations of the Jurassic, Cretaceous, Eocene Tertiary and Miocene Tertiary, were upturned =at the close of the Miocene period=."[92] With what a whack must this mighty mass of rocks have fallen on itself--miles in thickness, and turned "upside down over an area of 450 square miles"!!! Of course I am here taking the record just as I find it, as I have already discussed this matter of "overthrust folds."