1889.] THE DISPLACEMENT OF BEACH-LINES. 45 



of the curve which extend above the line, and the last-named 

 to those that lie below it. And if there are no gaps in the 

 series of beds there will be as many alternations of strata in 

 the marine, fresh-water, and land formations as there are periods 

 of precession in the corresponding arcs of the curve. 



To commence with I will take the profile obtained from the 

 Basin of Paris 1 , and will attempt to connect it with modern 

 days. I shall then speak of the Lower and Middle portion of the 

 Eocene epoch. 



The section from the Basin of Paris taken at Mery-sur Oise 

 (Bull. Soc. geol. Fr. 1878 p. 243 ff.) shows, in ascending order, 

 the following oscillations and alternations of strata, and may, in 

 respect of the continuous portion of it, be fitted into Sfoc/.-trc(('# 

 curve, in the manner that the numbers attached to the arcs 

 show for each oscillation: 

 Sables de Cuise, marine. 



Calcaire grossier, lower and middle, marine, with 7 alternations. 



Calcaire grossier: Caillasses a Cerithium, 2 marine alternations, 

 and between these a layer of fresh-water shells. 



Calcaire grossier: Caillasses a Lucina, marine with 5 alternations. 



Calcaire grossier: Caillasses a Cardium, marine, with 11 alter- 

 nations. A gap in the series of beds. 



Sables de Beauchamp, freshwater and marine, about 4 alterna- 

 tions. Arcs 14—15. 



Calcaire de St. Ouen, arcs 15—2': 4 freshwater alternations, 

 above them a marine bed (the apex of arc 16) and then 

 6 freshwater alternations. 



%psum, marine, about 11 alternations. Arcs 2'— 4'. 



Gypsum, palustrian, freshwater, about 6 alternations. Arc. 5'. 



Green Marl (Marne verte) brackish, 2 alternations. Arc. 6'. 



Calcaire de Brie, freshwater, 1 alternation. Between the arcs 

 6' and 7'. 



