354 ON THE MOVEMENTS OF THE EARTHS CRUST. 



laud and fresh- water formatious greater, the higher the place lay, aud 

 the shorter the time which it remained submerged in the sea, during each 

 oscillation. But this difficulty is of importance only when the continu- 

 ous profiles are so short that they do not embrace several oscillations. 



In the absence of longer, connected, and accurately traced profiles I 

 have first endeavored to determine the number of oscillations of coast- 

 lines as regards the Tertiary and Quaternary periods. Each of these 

 oscillations, of which there have been about thirty-six from the com- 

 mencement of the Tertiary period until now, has, in temporarily sub- 

 merged localities, produced an alternation of marine beds with fresh 

 water or terrestrial formations. To each more considerable oscillation 

 corresponds a geological " stage." In these " stages " there is a certain 

 number of alternations. By studying the literature of the Tertiary 

 basins of Europe I have in this way formed a combined profile, which, as 

 regards the alternations of strata, is not yet completed throughout, but 

 which efoes from the commencement of the Tertiary to the present time, 

 and which I shall now proceed to describe. 



The mode in which profiles can be compared with the curve to tes- 

 the correctness of the hypotheses is as follows: Each arc in the curve 

 will correspond to an oscillation of the sea. It is supposed that under 

 high latitudes the coastlines move up and down with the curve. Such 

 an oscillation I call a " geological stage." Each arc will therefore 

 have its corresponding oscillation or " stage," and in each "stage " there 

 will be as many alternations of strataas there are precessional periods in 

 the corresponding arc. When the eccentricity only sinks inconsiderably 

 between two or more arcs, the arcs run into one another, and form as it 

 were, ranges with two or three small summits. We have then "stages" 

 w^ith more oscillations and more alternations of strata than the ordinary 

 ones. We shall see examplesof this in what follows. We can draw aline 

 which indicates the boundary between marine and fresh-water forma- 

 tions. This line may he nearly or quite horizontal. Whether it is to 

 be drawn high or low depends upon how much above the sea the place 

 was situated where the deposits were formed at the time when the depo- 

 sition took place. The higher it lay, the higher must the line be drawn. 

 The place may have been so elevated that it never was submerged. 

 Then the lines are situated higher than the curve, and all the deposits 

 are fresh-water or terrestrial formations. But it may have lain so low 

 that it never rose above the sea, aud all the deposits are marine forma- 

 tious. But the line may cut the curve. Then marine formations alter- 

 nate with land and fresh-water formations. The former correspond to 

 those arcs of the curve which project above the line ; the latter to 

 those which lie below it. And when there are no gaps in the series of 

 deposits, there will be as many alternations of deposits in the marine, 

 fresh-water, and terrestrial formations as there are precessional periods 

 in the corresponding arcs of the curve, 



