Geological Society. 297 



shells, which seem to connect it with the period of the London clay. 

 We have further shown, that there are within the basin of the Upper 

 Danube two or three higher zones of lignite separated from each 

 other by sedimentary deposits of enormous thickness. 



The tertiary system of Bavaria is shown to pass into, and to be 

 identical with, the inolasse and nngeljlue of Switzerland. The higher 

 part of this series must therefore (on the system of M. Studer) be of 

 the same age with some of the formations of the Sub-Apennines. We 

 have proved that enormous masses of sandstone and conglomerate 

 many thousand feet in thickness, stretching from tlie base of the 

 Alps to the plains of the Danube, are chiefly derived from the degra- 

 dation of the neighbouring chain — that many of these masses cannot 

 be distinguished from the newest detritus which lies scattered on the 

 surface of the earth — that in their prolongation into Switzerland 

 they sometimes contain bones of mammalia — that they are regularly 

 stratified, and alternate with beds containing marine shells — and that 

 they cannot have been caused by any transient inundation. 



Finally, we point out the probable effect of debacles which took 

 place when the basin was deserted by the sea. We show that the ex- 

 cavations produced by the retiring waters have been augmented by 

 the bursting of successive lakes, of which we found traces in all the 

 upland valleys of Bavaria ; and that these excavations have been since 

 carried on by the erosive power of the streams which roll down from 

 the sides of the Alps to the plains of the Danube. 



The greatest number of tertiary formations hitherto described ap- 

 pear to have been produced either in estuaries or mediterranean 

 seas ; the depth of which, however considerable, was probably much 

 less than that of the wider oceans, wherein some of our secondary 

 rocks have had their origin. These circumstances tend to explain 

 the frequent alternations of marine and freshwater beds in the tertiary 

 seas ; and they satisfactorily account for the appearance of land shells, 

 lignite, and other terrestrial remains, drifted, at many different pe- 

 riods, into the regular marine deposits of the tertiary groups. By 

 the help of these alternations are certain species of marine and fresh- 

 water shells demonstratively shown to have been contemporaneous. 

 And when this conclusion is once established, it may be applied to 

 determine the age of those lacustrine formations which have never 

 communicated with the sea. 



In this way it has been shown that the enormous lacustrine depo- 

 sits of Aix in Provence, of the Cantal, of the Limagne d'Auvergne, and 

 of other districts in the south of France, belong to the period of the 

 great tertiary system of the Paris basin. I have no time even to allude 

 to the important works connected with these subjects, which we owe 

 to the naturalists of France : and the two Memoirs of Messrs. Lyt-U 

 and .Murchison," On the tertiary (lej)osit of the Cantal," and " On 

 the freshwater formitions of Aix in Provence," have been already 

 published*. I am not, therefore, called upon to give any regular 

 analysis of their contents. I may, however, be permitted to recall 



• See Edinburgh New Phil. Journal, Oct. 18'2!); and Avnalcs dei 

 Sciences Nalurelles, vol. xviii. p. 172. 



N.S. Vol. 7. No. 40. April 1830. 2 Q your 



