1889.] THE DISPLACEMENT OE BEACH-LINES. 57 



Above the Calcaire Grossier begins the upper Eocene, with 

 the continuous series of beds of the Paris basin described above. 



The lower and middle Eocene appear, thus, to contain 12 

 oscillations, of which 6 relate to each of the two subdivisions of 

 the epoch. With this the first cycle of the curve is filled out, 

 in such manner that the beginning of the cycle will about coin- 

 cide with the margin of the Chalk and Eocene. The middle 

 Eoceue has 25 alternations of strata in the Paris basin and 

 probably some breaks. 6 oscillations correspond to about 25 

 —30 periods of precession. 



At the commencement of the cycles the mean value of the 

 eccentricity is low, it increases in the middle of the cycle, and 

 again sinks towards the close. The position of the beach-lines 

 must also depend on the mean value of the eccentricity. But 

 as it increases very slowly, through very long periods, it will 

 be a very long time before its influence is visible on the solid 

 Earth. The middle of the cycles ought, thus, to correspond to 

 the transgressions of the sea, and the close, to the periods of 

 denudation that divide the formations. Breaks in the series of 

 beds may thus be expected in the higher latitudes, specially at 

 the limit between the cycles. 



The margin between Chalk and Eocene is indicated by what 

 Sum (vide Antl. d. Erde II, 7ter Abschnitt, p. 376 ff.) calls a 

 negative phase; the sea had retreated in the higher latitudes. 

 During the Eocene epoch it again rose, and the Eocene seas had 

 a wide distribution : we find their formations even in the centre of 

 Upper Asia. The margin between Eocene and Oligocene is again 

 distinguished by a negative phase. In the latter part of the 

 °»gocene epoch, and still more in the Miocene, the sea again 

 rose; between the Miocene and the Pliocene it retreated far 

 backwards, and in the beginning of the Quaternary epoch it 

 again rose. And similar great oscillations are traceable also 

 "i North America and in Patagonia. The Miocene marine beds 

 are - however, absent in the last-named place, where the Miocene 

 tosh-water beds are accompanied by great masses of volcanic 

 Product.. 



