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bouring region the same old volcanic rocks have risen to several 

 times that elevation. 



When we examine the upper rock marl of the Isle of Wight, we 

 see a deposit separated from us and the things about us, only by a 

 few feet of transported gravel. The outline of the country might 

 have been remodified and the gravel formed by some transient 

 inundation. We have therefore no measure of the time which may 

 have elapsed since the first existence of the phenomena before us. 

 If, however, we examine the shells in the rock marl, we find that 

 few, if any, belong to species existing in our lakes or rivers. We 

 cannot believe that there is so great a violation of continuity in 

 the forms of animated nature, except in subordination to nature's 

 laws ; and we feel almost forced to seek for a solution of our dif- 

 ficulties amidst the ideal revolutions of former ages. 



But how differently is the history of the same great period told off 

 among the volcanic mountains of the Cantal and Auvergne ! Great 

 lacustrine formations, of the same age with the rock-marl of the Isle 

 of Wight, are there proved by their organic contents to have been 

 formed and solidified at a time anterior to the trachytic eruptions 

 which upheaved and desolated the whole surface of the country. 

 How long these great eruptive forces were in action it is useless to 

 conjecture ; but they were followed by ages of repose, during which 

 the surface of the land was reformed, and deep valleys were exca- 

 vated by the erosive power of water. A new period of volcanic 

 agency succeeded, marked by domes of cinders and scoriae remain- 

 ing to this day almost unchanged, and by streams of lava which 

 maybe traced from them into the existing valleys. And even these 

 last operations, however recent in the order of geological events, 

 were anterior to the records of history; so that we can still only 

 approximate to their date, by a careful comparison of the effects 

 since produced upon these streams of lava by the destructive power 

 of the elements. 



A description by Mr. Murchison of the lacustrine strata and 

 fossils of GEningen is the last communication, connected with ter- 

 tiary formations, I am called upon to notice. He shows that 

 this deposit consists of horizontal beds of a considerable aggregate 

 thickness, laid bare in quarries on the side and near the summit 

 of a ridge of hills the base of which is washed by the waters of 

 the Rhine — that they do not alternate with the molasse but repose 

 upon it unconfonnably — and that from top to bottom they are of 

 freshwater origin. He enumerates in detail a great variety of fos- 

 sils (such as insects, plants, shells, fishes, tortoises, and mammalia,) 

 discovered at different times in these quarries ; and he adds a de- 

 scription (from the pen of Mr. Mantell) of a fossil fox not to be 

 distinguished from the Vulpes communis, found in the middle beds 

 of this system. From all these geological details, as well as from 

 the position of the strata, he concludes that they belong to a very 

 recent tertiary period. At the same time, the waters of the Rhine 

 descend from the lake of Constance at a level no less than 600 

 feet below that of the old lake in which the (Eningen beds origi- 



