424 A. Blytt o?i the prohable Cause of 



any alternation, 33'5 m. ; Middle Bagshot, 91 m. ; Upper 

 Bagshot (sand, without alternations), 37 m. ; Lower Headon, 

 21 m., Middle, 7 m., and Upper Headon, 26 m. ; Osborne 

 Series, 19 m. ; Bembridge Limestone, 7-6 m. ; Bembridge 

 Mar], 23 m. ; and Hempstead Series, 52 m. 



From Belo'inm we have the following thicknesses : — Mon- 

 tien (coarse limestone with Foraminifera), 93 m. ; Heersien, 

 32 m. ; Landenien, abont 60 m. ; Ypresien, 140 m. ; Bruxei- 

 lien, 50 m.; Laekenien, JO m. ; Wemmelien, np to 80 m. 

 (only determined by boring) ; Tongrien, 21 m. ; Rupelien, 

 60 m. ; An version, 3-4 m. (but near Utrecht, in an Artesian 

 well, 130 m.). 



The thicknesses in the basin of Mayence are as follows : — 

 Alzeyer Sand, 50 m ; Septaria-c\Ay ^ 50 m. ; Elsheimer Sands, 

 60 m, ; Cyr^?ia-marls, 40 m. ; C^jvY/imm-limestones, 25 m. ; 

 Corhicula-YimesioneB, 25 m. ; Litorinella-c\nj , 20 m. In Italy 

 Seguenza gives the following thicknesses : — Bartonien (in 

 part conglomerates, and perhaps several oscillations), 300 m. ; 

 Tongrien, 50 m. ; Langhien, Astien,and Saharien,each 200 m.; 

 Zaneleen, 300 m. The Swiss Mollasse (which is a shore- 

 formation) is so thick that it forms whole mountains ; but, 

 according to Charles Mayer-Eymar, the Aquitanian has a 

 much greater and, indeed, quite exceptional thickness near 

 Bormida, in Tuscany. Here we find (probably inclined from 

 the first) freshwater and superiorly marine shore-formations 

 with manifold alternations of sandstone and shales, the thick- 

 ness of which, although it has not been exactly measured, is 

 believed to be 3000 m., and all supposed to be formed in the 

 Aquitanian period. And the same stage (according to 

 Gumbel) has a similar thickness in Bavaria. Etna, which is 

 12,000 feet high, has been built up by volcanic eruptions in 

 the most recent geological period, and since the Mediterranean 

 had acquired a fauna essentially the same as at the present 

 day. 



The formation of the Mediterranean, with its strong vul- 

 canism, has been distinguished (according to Suess and Neu- 

 mayr) by very considerable displacements of the earth's body. 

 The Egean Sea and the Adriatic have been formed by depres- 

 sions in the latest geological period. Under such circum- 

 stances, very thick deposits may be formed near land in a short 

 time. Eocene marine deposits are uplifted 21,000 feet above 

 the sea in folded ranges (e. g., in Upper Asia). But all these 

 are only local disturbances. If we turn, on the other hand, to 

 localities where the conditions have been more quietly deve- 

 loped, we find, as may be seen from the preceding statements, 

 that the stages have only a small thickness, The deposits 



