CVlll rEOCEEDlNGS OF THE GEOLO&ICAL SOCIETY, 



I. Pormatiou of mountains and A-alleys by elevation and sub- 

 sidence of the land. Science has not yet come to any conclusion 

 as to the causes which have led to these phenomena. The hypo- 

 theses which have been imagined to explain these mighty opera- 

 tions of nature are connected with the views respecting the forma- 

 tion and the original condition of the earth ; and the contest w'hich 

 has been going on for 2000 years, whether fire or water has had 

 the greatest share in it, is not yet decided. But the mode of 

 operation is visible in a thousand ways ; and the author proceeds 

 to show how the endless variety of mountain-forms and valley's has 

 been the result of the elevations and subsidences of the previously 

 horizontally-bedded strata, influencing the surface-distribution of 

 water as well as the contotu' of the land. He describes the various 

 risings and sinkings of the land which have taken place in Switzer- 

 land, and which were generally of a very gradual character; but this 

 remark does not apply to the last Pliocene elevation of the Alps. 



II. By the effect of water. The streams which flow from the 

 mountains received their first direction from the forms of the 

 mountains themselves and the disturbed strike of the stratified 

 rocks, although in the coiu^se of thousands of years they have 

 deepened their beds and widened their channels. It would only 

 occur to the wildest Neptunist to maintain that such gorges as 

 the Via Mala and others have been excavated by the Bhiue, &c., 

 although undoubtedly these streams, flowing through original 

 cracks and crevices, have gradually widened and deepened them. 

 It is otherwise in the Molasse country, where the valleys and 

 river-beds are generally the work of erosion. These began in the 

 Pliocene period during the elevation of the Alps ; and when after- 

 wards the glaciers descended from the mountain-tops, they filled 

 up the valleys and lake-basins with ice, and thus protected them 

 from being filled up by the gravel and other materials which they 

 brought down from the mountains. 



III. Modification of the surface of the land by the climates of 

 the diff'erent periods. Amongst other causes of a change of 

 climate, Professor Heer again refers to the probability that diu'ing 

 the Miocene period a great Atlantic continent extended from the 

 w'estern shores of Europe to the east coast of America, stretchiug, 

 in the form of a promontory, from Iceland in the north to the 

 Atlantic Islands in the south. Thus we can understand how the 

 Tulip-tree existed in Ireland and in Switzerland, while many other 

 phenomena both in the Flora and Fauna of the Miocene age are 

 accounted for in the same way. But I must refer you to the 

 W'ork itself for the interesting observations contained in this 

 chapter respecting the change in the configuration of the Eu- 

 ropean continent and the surrounding region, which took place 

 during the Pliocene age, and the diluvial period which followed 

 it. These are becoming daily of more importance in connexion 

 with those recent changes which accompanied man's first appear- 

 ance, and led to the present configuration of tlie earth's surface. 



The second part of this chapter refers to organic nature. The 

 author show^s that there ai'e no sharply defined lines of separation 



