18 Anniversary Address of the 



conclude that formerly, as now, the rate of change in the 

 vegetable kingdom was extremely slow, so that a stupendous 

 mass of stratified sand and mud, as well as great revolutions 

 in physical geography, might be slowly effected, without there 

 being time for any important fluctuation to be brought about 

 in the species of plants inhabiting the globe. 



I have endeavoured to shew in my " Second Visit to the 

 United States,"* that a great oscillation of level has taken 

 place in the valley of the Mississippi and its tributaries, by 

 means, first, of a slow downward movement, and then of an 

 ascending one, and that the whole was accomplished since 

 the period when the freshwater and land-shells now inha- 

 biting that great valley were already in existence. We ought 

 not therefore to be surprised when we discover sea-beaches 

 in Norway 700 feet high, in which the shells are identical 

 with those now inhabiting the German Ocean ; for we have 

 already seen that the rise of land in Scandinavia, however 

 insensible to the inhabitants, is rapid when compared to the 

 rate of contemporaneous change in the testaceous fauna. 

 Were we to wait therefore until the mollusca shall have 

 undergone as much fluctuation as they underwent between 

 the period of the liassic and upper oolite formations, or still 

 more between the oolite and chalk, or between the Wealden 

 and eocene strata, what stupendous revolutions in physical 

 geography ought we not to expect, and how many mountain- 

 chains might not be produced by the repetition of shocks of 

 moderate violence, or by movements not even perceptible by 

 man ! I may take this opportunity of stating, in reference to 

 the permanent effects of subterranean movements in our 

 times, that in all likelihood we are always in danger of un- 

 derrating their intensity, because we can only measure their 

 amount on the sea-coast, whereas the adjoining mountain- 

 chains seem generally to be more shaken by earthquakes, 

 and probably undergo a greater change of level than the low 

 countries. 



Let us now return to the Alps, and inquire whether geolo- 

 gists who ascribe their origin to paroxysmal forces have been 



* Vol. ii. chap, xxxiv. 



