Geological Society/. 139 



proved by M. Brongniart to be of a date probably as ancient as 

 the upper fresh-water strata at Paris. 



The only difference remaining between the ancient and the 

 modern fresh-water formations is, 1. the absence in the latter of 

 silica, which is only known as a modern deposit from water con- 

 nected with volcanic agency; and 2. the small scale on which the 

 recent accumulations proceed. 



If these differences are ascribable to a higher temperature pre- 

 vailing where the ancient fresh-water rocks were formed, they 

 may perhaps disappear when the hitherto unexplored tropical 

 regions of the globe are fully investigated. 



A paper was also read, entitled. On the Fresh-water forma" 

 iions recently discovered in the environs of Sete (Cette)^ at a 

 short distance from the Mediterranean, and below the level of 

 the Sea; by M. Marcel de Serres, Prof, of Min. & Geol. to the 

 Faculty of Sciences of Montpellier. 



The fresh-water formations described in this communication 

 have been examined by means of several wells sunk at about the 

 distance of three-quarters of a mile, and a mile and a half, from , 

 the Mediterranean, near Sete, in the South of France. 



A detailed account is given of the several strata passed through 

 in the three different wells, and of the organic remains which they 

 contained. 



The strata are for the most part parallel and nearly horizontal. 



From the sections it appears that there are two fresh- water forma- 

 tions with an intervening formation of marine origin. The strata 

 of the upper fresh-water were found to vary from about 30 to 40 

 feet in thickness, those of the lower from 13 to 28 feet, the latter 

 being sometimes lower than the present level of the Mediterranean. 



The marine beds which are interposed are from 10 to 11 feet 

 thick. 



The fresh-water strata are composed of numerous alternating 

 calcareous and argillaceous marls, and compact limestones; and 

 their organic remains consist of a few bones of land quadrupeds 

 much decayed, a variety of fresh-water and terrestial shells, the 

 latter in the greatest abundance; the shells differing in species 

 but not in genera from the present inhabitants of the same country; 

 and lastly some traces of vegetables, chieily reeds. 



