SLOW UNDULATIONS OF THE CRUST. 



tracts, formerly covered, dry. Considering the solid and appa- 

 rently permanent character of the land on the one hand, and the 

 extreme mobility of water on the other, such a conclusion was 

 natural, and almost inevitable, until clear evidence of the con- 

 trary was obtained. It has, however, been proved that the very 

 reverse has been the case of such phenomena, the mobility apper- 

 taining to the land, and the permanence to the sea. It has been 

 shown, by observations made upon the level of the ocean, that it 

 has not suffered any general change within historic times ; but, 

 on the contrary, that the cases in which the land has been inun- 

 dated by the ocean must be ascribed to the sinking of the land, 

 and those in which the waters have deserted their bed to the 

 rising of the bottom of the sea. 



118. These changes in the level of the crust of the earth have 

 been in some cases sudden, as when they are produced by earth- 

 quakes, but in others they have been so gradual that they could 

 only be ascertained by observation extending over long intervals 

 of time. It had been long observed in different parts of Sweden, 

 that the level of the surrounding ocean was subject to an apparent 

 but slow and gradual change, in some places rising, in others 

 falling. The Academy of Upsal, in 1731, commenced a series of 

 observations with a view of determining the fact whether this 

 apparent change of the ocean were real, or whether it were not 

 caused by an actual change in level of the land. Marks were 

 accordingly cut upon the faces of rocks at the level of the sea, and 

 at the end of some years these marks were several inches above 

 that level, from whence it was in the first instance inferred that 

 the Baltic had suffered a depression of its level, so as to leave 

 more or less of the bottom dry. These observations, however, 

 being continued and multiplied, it was soon rendered apparent 

 that, while the level of the Baltic remained unchanged, the 

 phenomena were produced by actual changes in the level of the 

 land. It was found that the apparent depression of the level of 

 the ocean was different in different places, and that in some 

 places, on the contrary, it appeared to have been even raised. 

 Thus, while at certain points the apparent depression amounted to 

 several inches, in others it did not exceed a fraction of an inch ; 

 at some places, such as the coast near Christianstad, the level of 

 the sea appeared to be elevated. The conclusion deduced from 

 all these observations was, that the apparent change of level of the 

 sea was produced by a slow and gradual upheaving of the land in 

 some places, and a sinking in others ; that in Finland, and in a 

 great part of Sweden, the surface was gradually raised without 

 any perceptible shock, while in the southern parts of the peninsula 

 a corresponding depression was produced. 



91 



