26 A. BLYTT. [NO. 1. 



Sand, calcareous sandstone, marine .... 2.0—2.3 m. 



The same, fresh-water 3.0 „ 



Sand, clay, ironstone, marine 5.0—6 „ 



Clay, limestone, iron-sandstone 5.0—7.0 „ 



Sand, marls, iron-sandstone, lignite . . . . 30 — 60 „ 



In each stage there are usually, when there has only been 

 one oscillation of the sea, 4—5 such alternations, so that the 

 thickness of the stages is only small as a rule. I will give the 

 following examples. First from the Basin of Paris: Calcaire 

 grossier, which represents 25 alternations, and several, 5—6 

 oscillations, is only 31.5 m. in thickness; sables de Beauchamp 

 13—14 m.; Calcaire de St. Ouen, having 10 alternations, is 

 only 6—7 m. in thickness; gypse marin 16— 17 m.; gypse palustre 

 20 m.; sable d'Etampes 11—12 m. The beds of the Isle of 

 Wight are thicker, but also richer in mechanical deposits: 

 Plastic clay 26 m.; London clay 61 m.; Lower Bagshot (sand, 

 clay, lignite, iron-sandstone, 7 alternations) as much as 200 m.; 

 Bracklesham of same description as the last, but without any 

 alternation 33.5 m.; Middle Bagshot 91 m.; Upper Bagshot (sand 

 without alternation) 37 m.; Lower Headon 21 m.; Middle Hea- 

 don 7 m. and Upper Headon 26 m.; The Osborne stage 19 m.; 

 Bembridge limestone 7.6 m.; Bembridge marl 23 m.; The Hemp- 

 stead stage 52 m. From Belgium we have the following thick- 

 nesses stated: Montian (coarse limestone, containing foraminifera) 

 93 m. ; Heersian 32 m.; Landenian about 60 m.; Ypresian 140 m. ; 

 Bruxellian 50 m.; Laekenian 10 m.; Wemmelian up to 80 m. 

 (only arrived at by boring); Tongrian 21 m.; Eupelian 60 m.; 

 Anversian 3-4 m. (but near Utrecht 130 m. in an Artesian 

 well). The thicknesses in the Basin of the Maine are as follows: 

 AlzeyersandSO m.; The septaria clay 50 m. ; Elsheimersand 60 m. ; 

 Cyrena marl 40 m.; Cerithium limestone 25 m.; Corbicula lime- 

 stone 25 m.; Litorinella clay 20 m. From Italy, Seguenza states 

 the following thicknesses: Bartonian (partly conglomerates and 

 probably several oscillations) 300 m.; Tongrian 50 m.; Langhian, 

 Astian and Saharian each 200 m. ; Zanclean 300 m. The Swiss 

 Molasse (where it exists as a beach formation) is so thick that 



