1889]. THE DISPLACEMENT OF BEACH-LINES. 65 



rise and fall of the eccentricity of the Earth's orbit. That is 

 the case in respect of both, the respective arcs of the curve 

 and of the cycles. In such a cycle „the mean level of the sea" 

 rises and falls once in 16 oscillations. 



The sidereal day has (cfr. Darwin) become several hours 

 longer. It is therefore probable that there must have accumul- 

 ated such a great strain in the mass of the Earth, that a 

 slight increase of the strain would be sufficient to cause changes 

 of form at the weakest points. It is also likely that those par- 

 tial changes in the solid mass of the Earth must occur, especially, 

 at times of great eccentricity, or some time after such an oc- 

 currence, when the motive force increases quickest. 



The change in the tidal-wave caused by the variation of the 

 eccentricity, is presumed to be sufficiently great to explain the 

 displacement of the beach-lines. A few metres of vertical displace- 

 ment of the beach-line is sufficient to produce, in the deeper 

 basins, an alternation of many metres of thick marine and fresh- 

 water beds. And as regards the changes in the solid body of 

 the Earth, we must recollect that the series of beds is not com- 

 plete at any single spot. In other words, the oscillations were 

 not general to such an extent that they were contemporaneous 

 everywhere. Only by partial changes of form, sometimes here, 

 sometimes there, always at the weakest points in each age, has 

 the solid Earth approached to the spheriform. To each arc of 

 the curve there corresponds, therefore, only a partial and not a 

 general change in the form of the solid Earth. And the oscil- 

 lation of the beach-line, corresponding to the arc can, therefore, 

 not be pointed out everywhere, but only in the basins where 

 the forces at that time exerted their effect. In this way we 

 can obtain a perfect profile only by combining layers of all the 

 Tertiary basins. Neither were the changes of the solid Earth 

 everywhere equal in extent, but were greatest at the weakest 

 P°ints of its surface, so that quite extensive local upheavals may 

 he caused by slight changes in the length of the sidereal day. 



That is the case as regards the individual oscillations, but 

 ey en the great transgressions of the sea, of which one occurs 



Vid.-Selsk. Forh. 1889. No. 1. 5 



