298 COSMOS. 



about 320 feet in the space of 8000 years; and in 12,000 

 years, if the movement be regular, parts of the bottom of the 

 sea \\hich lie nearest the shores, and are in the present day 

 covered by nearly fifty fathoms of water, will come to the 

 surface and constitute dryland. But v^liat ace such intervals 

 of time compared to the length of the geognostic periods re- 

 vealed to us in the stratified series of formations, and in the 

 world of extinct and varying organisms ! We have hitherto 

 only considered the phenomena of elevation ; but the analo- 

 gies of observed facts lead us with equal justice to assume the 

 possibility of the depression of wholo tracts of land. The 

 mean elevation of the non-mountainous parts of France 

 amounts to less than 480 feet. It would not, therefore, re- 

 quire any long period of time, compared with the old geog- 

 nostic periods, in which such great changes were brought 

 about in the interior of the earth, to effect the permanent 

 submersion of the northwestern part of Europe, and induce 

 essential alterations in its littoral relations. 



The depression and elevation of the solid or fluid parts of 

 .lie earth phenomena which are so opposite in their action 

 ihat the effect of elevation in one part is to produce an appar- 

 ent depression in another are the causes of all the changes 

 which occur in the configuration of continents. In a work of 

 this general character, and in an impartial exposition of the 

 phenomena of nature, we must not overlook the possibility 

 of a diminution of the quantity of water, and a constant de- 

 pression of the level of seas. There can scarcely be a doubt 

 that, at the period when the temperature of the surface of the 

 earth was higher, when the waters were inclosed in larger 

 and deeper fissures, and when the atmosphere possessed a to- 

 tally different character from what it does at present, great 

 changes must have occurred in the level of seas, depending- 

 upon the increase and decrease of the liquid parts of the 

 earth's surface. But in the actual condition of our planet, 

 there is no direct evidence of a real continuous increase or de- 

 crease of the sea, and we have no proof of any gradual change 

 in its level at certain definite points of observation, as indi- 

 cated by the mean range of the barometer. According to ex- 

 leriments made by Daussy and Antonio Nobile, an increase 

 in the height of the barometer would in itself be attended by 

 a depression in the level of the sea. But as the mean pressr 

 ure of the atmosphere at the level of the sea is not the same 

 at all latitudes, owing to meteorological causes depending upon 

 the direction of the wind and varying degrees of moisture, tho 



